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Electric Car Conversion
9

Electric Car Conversion

Electric Car Conversion

(OP)
How have I missed this forum until now? Wow, I've been missing the really good stuff!!!!

As my handle may suggest, one of the things I do for fun is to melt metal. I've built a simple propane-fired box kiln and pour brasses and bronzes mostly, using home-made greensand and more recently oil-bonded sand molds. I make mostly drawer pulls and knobs/handles and even a few chisel planes, all for one of my other passions- my woodworking projects.

But I got bored...so time for something new!

I've owned a 1975 Triumph Spitfire since the late '80s when I was in uni and wanted to learn about cars from my dad, a long-retired auto and diesel mechanic. Oh, and it taught me, the hard way- the Leyland 1500 engine was an utter piece of crap, disappointing me numerous times. I put a Toyota 20R engine and transmission in it in the early '90s, but it never really fit the car. The last sticker on the license plate was the year I moved in with the girl who DIDN'T like this car- we've been married now for 15 years. I kept the car though, with the intention to do something fun with it some day.

My son is 11- old enough to be useful (when he can be pried away from video games), but young enough to still think what his dad does is worth paying attention to. So the two of us have embarked on an electric conversion of the Spitfire. Goal is a daily driver for my commute in the spring, fall, and days in the summer where the lack of A/C won't roast me to death. 60 km one way, with a charge at work to get home.

Current status is that we've pulled the engine, exhaust system, gas tank etc., separated the body from the frame, restored the frame (lots of practice welding!), painted it with surface tolerant epoxy, replaced the brake lines and hoses, and ordered the parts for the conversion. Body is going to take quite a bit of work- floor pans, rocker panels etc.

Going with an AC system- a HPEV AC50 motor and Curtis controller, and LiFePO4 prismatic cell battery pack. I've seen lots of conversions done using this system including this one, which used an AC51 (just a higher voltage version of the AC50):

http://www.youtube.com/watch?v=BlSb4It9ZdY

(warning- language- and make sure you watch the guy come back around the corner a couple times!)

Should be a fun car when I'm done!

Will be no doubt asking lots of questions here, as well as on a particularly good DIY electric car forum.

RE: Electric Car Conversion

My brother had a Spitfire...I "borrowed" it one day when he wasn't home. The radiator boiled over about 4 miles from home...and I spent a panicked hour or two finding decent water and containers to refill it and get it back in its parking spot before he came home again. I don't remember how, but he knew I'd moved it.

RE: Electric Car Conversion

Welcome to the forum moltenmetal. Glad to have you.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

Succeed or fail, your boy is going to think very highly of the experience in 15 years time, and wonder why most people around him don't understand much about the physical world around them.

RE: Electric Car Conversion

(OP)
I hoped the educational opportunity for my son would warm my wife's heart toward the project, but no dice. She hates that car...and has a long list of furniture projects for me to complete which of course cannot be done now because the car is in the way. I've never liked my hobbies being turned by others into work- I have enough work in my life already, thanks!- so the car's a blessing!

My son is great when there's a task he can tackle on his own, with help available when he needs it. He has no patience for fetching tools, which I could do for my dad for hours. Struggling to find things he can do on his own without mucking things up- was easier when there was stuff to take apart that wasn't needed in the finished car.

RE: Electric Car Conversion

Let him muck up some. That is a valuable learning experience.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

Good choice of "donor" car, light frame, and doesn't need power steering IIRC.

My privileges may be suspended for doing this, but..
... look through this other forum: http://www.diyelectriccar.com/forums/ (unless that's the one you're already found, of course)
and this may also provide inspiration: http://www.evalbum.com/

I've been watching those guys for a while, but haven't quite jumped in yet. Maybe I ought to hurry up. My son just turned 13.

STF

RE: Electric Car Conversion

(OP)
Thanks SparWeb- I found that forum a long time ago, before I decided to go through with this conversion. Very useful and helpful with all the decisions about what conversion parts to get, the benefits of the LiFePO4 cells, pack balancing and battery management etc. There's a "garage" with quite a few converted Spitfires in there, and quite a few brains to pick!

Tough decision though- I'm fundamentally a cheapskate, and just the parts for the conversion have been expensive, beyond what I wanted to spend by at least a factor of two. I was tempted to go the total DIY route, salvaging an old forklift motor, getting a Chevy Volt pack from a wrecker and chop-shopping it, building a kit motor controller etc., but the spend on the battery pack alone was so substantial for my required range that it didn't make sense. I'm too much of a cheapskate still to be spending any of this money twice! That seems to be a common theme with these conversions- people cheaping out, then going back and spending more money to replace something which was unsatisfactory. I'm sure I'll tinker with it forever, but I do hope that the Leyland evil spirits that stranded me repeatedly at the side of the road will be well and truly purged by the time I'm done!

The kid was a big help last night- right in there with me, scraping away the remnants of the carpet underpad while I sliced away rusted bits of the remaining floor pans with the angle grinder- I'm getting to be a surgeon with that thing. I've definitely got nothing to complain about with respect to this kid! He likes painting, which I hate...I think the bodywork is going to be something he'll enjoy and will definitely be able to contribute to. Plus there's still a lot of stuff to disassemble that I didn't get around to yet- he can pull the ignition coil, heater core hoses, starter relay and a bunch of other crap I left attached to the body bucket when we pulled it. I'm sure there's something for him to help with at every stage.

Yeah, get on it! 13's not too old- he'll be able to contribute a lot! And if my experience so far as been any indication, the father-son time working together will be worth whatever it costs.

As to letting him muck things up, I don't mind it at all- I do plenty of it myself. This car's a wreck already so there's really nothing irreparable that he can do to the thing, assuming I'm around to keep him from getting himself hurt of course. But I do need to jump in when he's about to round or snap off a bolt that I'll have to extract from some horrible location etc. The two of us had to fight for two hours with one of the four bolts which held the gas tank in place- the threaded boss tore out of the sheetmetal. It was like the car was clinging on to its fossil fuel addiction...

RE: Electric Car Conversion

(OP)
Progress update: after many hours of grinding, power wire brushing, welding, tin-whacking and cursing, new floor pans were fabricated for the car- Fred Flintstone would no longer be able to drive it. Body is back on the frame, all the crap removed from the firewall and the shelf above it, and it was epoxy coated too. Rocker panel replaced on one side, patched on the other- but still lots of rust patches to fabricate and weld in, then endless bodywork this winter to make it look pretty. The electric motor is installed (the hub to mount the flywheel and the transmission mounting plate I bought were both perfect fits- well worth the money spent), and the main 2/0 cable runs between the front and rear battery packs have been pulled- 1/2" ENT conduit throughout for extra protection of the conductors under the car, but nowhere is the cable a low point. Batteries come in a week or two, at which point I'll begin laying out the main electrical components and start wiring. A few brake parts to go in yet- redid all the brake lines and hoses with a cupronickel line kit- beautiful stuff to work with. Found some nice leather Miata seats at a wrecker that got a little crispy on the headrests when the soft top of the car caught fire, but nothing that a little clever sewing can't fix by means of some headrest cover "bags"- hoping to convince my wife, who is an expert cutter, tailor and seamstress, to do that for me- for money of course, but since she hates this car with a passion- even money may not be enough.

Hoping to get the kid involved more in the wiring- he got bored of watching me weld and grind pretty quick.

RE: Electric Car Conversion

Who can blame him? It's summer.

I found a MG chassis that's been stripped and re-painted, but the owner hasn't bothered to reassemble. Almost perfect for an EV conversion. I still haven't convinced myself to do one of these so I haven't mentioned anything to the owner yet. He's an old-school type so he might not sell it to me if I let him know my intention of stuffing it full of electrons, not pistons. But I sure am deep in research mode. Found two similar conversions, one thoroughly documented on a website. Looks like a 9" Impulse is all a MG would need, both a good fit in the space and power to hustle it along. I'm not thrilled by the range reported by the builders of the two MG conversions I've seen so far. Not much room for batteries in those 2-seaters. They may have preserved too much trunk space. The entire electrical system would be "carte blanche" so to speak.

STF

RE: Electric Car Conversion

The two builds I've looked at so far both use the same LiFePO4 cells (Thunder Sky) and the same motor (Warp 9 Impulse series-wound). One uses a Zilla and the other a Soliton controller but I think the main difference in range comes from one carrying 3800 AH of charge and the other 6000 AH. The one with the larger bank is reported to get 80 miles when discharging the cells down to 80% DOD. I guess for a homebuilt conversion it's good but it barely gets me to work and back.

STF

RE: Electric Car Conversion

There shouldn't be much range difference with controllers, maybe 1 or 2%. Basically it depends on how many high quality FETs they use in the output stage, for solar cars we used to fit $8000 controllers, as it was a relatively cheap performance boost.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

Just buy a Tesla...

Mike McCann, PE, SE


RE: Electric Car Conversion

Roughly speaking a normal electric car conversion will manage about 5 miles per kWh, with exceptional design double that is possible. A solar car manages about 60 miles per kWh, and a lightweight streamliner could double that due to lower drag and weight.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

I've seen much the same - though it's hard to sort out the actually-measured from the predicted-to-be projects that aren't finished yet, when reading about this on the internet.
Using a simple 200 Wh per mile, or in my case 120 Wh per kilometre, then I'm going to need at least 15 kWhr of charge to do my daily round-trip, 120 kilometres.
Bigger picture: an EV conversion project will take several years to complete, but in the near future I have to demolish my mouldy old garage and build a new one. It really must go. I would much rather spend all that time to build an EV in a garage with a nice shop space, and without the mould. If a new garage is under way, then I ought to arrange the roof to take a few solar panels, too, huh?

STF

RE: Electric Car Conversion

Speaking of the realtionship being EV's and solar projects, the CEO of Tesla, Elon Musk, is also the chairman of Solar City.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

RE: Electric Car Conversion

Conflating or linking electric cars with solar power seems to be more greenwash marketing than actually practical at this point in time.

One company (Nissan?) is marketing solar panel installations for your house, so you can recharge you eCar using solar power, presumably at night.

RE: Electric Car Conversion

(OP)
My pack will be 32 x 180 Ah Sinopoly LiFePO4 cells which average about 3.2 V each. I'm counting on 300 Wh/mile on the highway with my fairly lightweight and small (narrow, low) but not very aerodynamic car. That should require about 12 of my 18 kWh of stored energy for my 37 mile commute, which is bit below 70% depth of discharge, where these cells apparently last around 3000 charge/discharge cycles. Will be able to charge off an ordinary 120V outlet, but I did buy the expensive socket for a Type 2 charger should I ever run into one.

I went AC, both because I didn't like the thought of brushes and their maintenance, and because I wanted the regenerative braking, not just for the range improvement but because the car has rear drums only and the brakes are 100% mechanical. I have an HPEVS AC50 with a Curtis AC controller- motor's already in, I'm laying out the various parts on a piece of plywood to figure out the best way to fit everything. The car will be capable of pushing 500-650 A forward and 200 A reverse on regenerative braking. The plan right now is for 100 A to come on when I take my foot off the accelerator- kind of like the "drag" you get on an automatic transmission car- and another 100 A to come on with the early travel of the brake pedal. I'll have a pot so I can reduce that to zero in bad weather if I start locking the rear wheels.

Regrettably I'm down another car- fortunately nobody was hurt, but my 2008 Prius is probably a write-off. Ran a stopsign that was completely hidden by tree boughs. Wow, those crumple zones work- neither cars' airbags went off. But mine is likely toast, which is a shame because insurance won't give me what it's worth to the family as transportation...

Yeah, it's summer, but the kid spends his time inside playing video games unless we kick him out...it's both fun and his way of socializing with his friends- tough to compete with it.

RE: Electric Car Conversion

I'm not advocating solar for street cars, that was just a point of reference. The Volt and the little Nissan are useful estimators for energy per mile, 3 and 4 miles per kWh roughly in the real world (should have checked this before).

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

Quote:

...One company (Nissan?) is marketing solar panel installations for your house, so you can recharge you eCar using solar power, presumably at night.
Yes the marketing message behind this is best not scrutinized too closely. I've seen this in Pop Science/mechanics magazines, and of course it always relies on the power grid to be your "battery" to make this work.

Moltenmetal,
Thanks for the extra info about your plans. I too would like to use an AC system but it's still not the norm. I would rely upon some expert advice to choose components and integrate them properly - there are some EV conversions that use AC (on EV Album) that clearly do not perform well.

Sorry to hear about the Prius biting the dust, too.
Curious about something: I've been in some nasty collisions too. When the firefighters arrive, they are pretty aggressive about rendering the car inert. Cutting battery cables and so on. Presumably with an EV this could be very invasive indeed, even counter-productive in a home-built EV. Did anything of the sort happen at your accident scene?

STF

RE: Electric Car Conversion

My solar cars use a wheel motor, with 3 phases of shaped DC pulses, electronically commutated. We use them because they are very efficient (98.4% at the optimum). The guts of the motor aren't expensive, and is more or less the same as the type used in Fisher and Paykel washing machines.

http://www.csiro.au/Outcomes/Energy/Powering-Trans...

I'm not a huge fan of wheel motors for production cars, but I think the advantages of that location are so great that it will become inevitable down the track as cars get (hopefully) smaller.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

Why have you and CSIRO referred to them as "solar car" motors? Surely the motor can be used on an electric vehicle, with our without solar panels? Is this purely a question of unsprung weight? Or that it is acceptable on a solar car, where many such trade-offs have already been made, versus a road car, in which a certain handling quality is expected?

STF

RE: Electric Car Conversion

Did I call them solar car motors? Well, that's what that design is, it would probably overheat if used for a real car, it's a 5 kW motor not 20-30.

I'm not too worried about the ride issues from them, I just don't like relatively expensive/fragile electronic bits out on the wheels.

Ride issues were investigated by Lotus and Damian Harty they didn't seem very worried.

http://www.proteanelectric.com/en/wp-content/uploa...

Mr Hurdwell and the younger of the Andersons also had a look

http://www2.eng.cam.ac.uk/~djc13/vehicledynamics/d...


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

(OP)
The Prius's front end was bashed quite a bit- very square-on tee-bone collision. Her damage was localized only to the passenger side front door and for some reason a flat passenger side front tire. We didn't need emergency services- no injuries aside from to my pride, no fire, and both front doors remained operable. My car did lose its coolant- the first thing to go on a Prius in a front end collision is the thermos bottle that holds hot coolant to get the engine up to temperature faster after a stop- but my rad is also squashed so coolant was going regardless. The police when called originally said they wouldn't need to send anyone because there was no injury, but there was a policeman on site in at most five minutes. He investigated on site and documented the stop sign condition- I have photographs too- but it won't help - in a collision like this, even if the stop sign was missing entirely it would still be assessed as my fault.

Rule of thumb that the EV conversion crowd use is that the Wh/mile correlates well with the weight of the vehicle in pounds/10. A Chevy Volt apparently has a range of 61 km on a 16.5 kWh pack which is used to something less than 70% DOD before the IC engine is switched on- almost dead on 300 Wh/mile, but that car is both greatly heavier and more aerodynamic than mine, so there are factors both ways. I figure on highway speeds all the way in the morning so I went with 300 Wh/mile to be conservative.

The AC systems that have sucked are either chopshop combinations of industrial induction motors and VFDs or transmissionless/clutchless conversions unless I'm missing something. Here's an example of a VW Beetle conversion done with an AC51, which is the same motor operating at higher voltage- same torque, modestly more peak horsepower than what I'm using. Make sure you watch him come back around the corner and do a burn-out start- well into the video, and warning, the language gets a little "excited" when they see how well the car performs...

http://www.youtube.com/watch?v=BlSb4It9ZdY

I'm not expecting mine to behave like that, but having up to 120 ft-lbs of torque available at near zero RPM should make for a fun drive! Even that 2.2L Toyota 20R that I had in it didn't generate that kind of torque until you were well up in RPM.

RE: Electric Car Conversion

The only problem with AC motors is that the controller electronics cost more (AC locomotives are in the order of a $1 million more than DC locomotives). Just know they cost more.

AC motors are typically very rugged, so I would see no reason to be concerned about them as wheel motors. Except if you have non-electric issues like too much force on the bearings, or vented motors.

If you don't like brushes, don't AC motors have brushes? Maybe not all of them but some types do. The ones that don't have brushes (assuming you need slip in one or more wheels and you only have one AC controler, and not one for each motor) is an induction motor, which won't allow dynamic breaking. So I assume they aren't induction motors. Therefore you most likely have a controller for each motor, which is why AC controllers cost more.

RE: Electric Car Conversion

A four quadrant drive has no problem with dynamic/regenerative braking of an induction motor.

RE: Electric Car Conversion

"...my 2008 Prius is probably a write-off..."

Glad to know that everyone is okay.

Does this accident perhaps offer up any useful e-car parts for your project? Depending on how insurance works in your area, you might be able to buy the written-off car from the designated junk yard for a slight markup (e.g. $400) over some agreed fraction (e.g. 40%) of the Write Off value (i.e. what the junk yard pays the insurance company).

RE: Electric Car Conversion

david, you are correct. I missed that. But it is more limited to how low it can go in speed for regeneration.

RE: Electric Car Conversion

(OP)
VE1BLL: good suggestion, but unfortunately or fortunately I have all the kit I need for my other car aside from horns and perhaps the A/C compressor- but I would imagine that was all up front too and probably damaged. It would be tough to use a Prius drivetrain in a rear wheel drive conversion, and the battery pack is pretty much useless for an EV- it's apparently only 2 kWh and very high voltage. Now if I knew this was going to happen beforehand, I might have had to do some serious thinking...Surprisingly, my wife was also onto this thought around the same time that I was- she had visions of another hulk of a car hanging around the place with me salvaging parts off it, and that was NOT in the cards as far as she was concerned! This was the family car, i.e. her car, so she's the one who will be suffering as a result of my mistake- but she's glad it happened to me instead of to her as she knows she'd never hear the end of it from me!

RE: Electric Car Conversion

Tesla's claim works out to about 8 mi/kWh, but let's say it's 4. Then, for me, with a 400 mi/wk net travel, that would be 100 kWh per week, and about 430 kWh per month, which would put me further into Tier 4, and they might even create a Tier 5, just for me poke. Tier 4 is 34 cents/kWh, so that's $146/mth. That's only barely better than what I pay for my Prius' gas now, and that's only because I'm a bit lead footed. The only way an electric car would be significantly better would be if I had a separate electric service just for the charging station, which might drop me down to Tier 1 or 2, with Tier 1 being only 14 cents/kWh and Tier 2 being 16 cents
.

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RE: Electric Car Conversion

"AC electronic controllers cost more..." but they typically include regeneration braking, while DC controllers don't, so you get more.
"AC motors have brushes..." Some do, but many don't. The vast majority don't, in fact.

Correct me if I'm wrong, but the only AC motors with brushes are field-excited types (whose speed can be controlled by adjusting the current in a winding on the rotor). That style of motor has been on the decline for decades.

When discussing AC motors now, I believe most people assume you are talking about an induction motor, with no brushes or magnets or field windings at all. Just those induction bars encased in the rotor core. If talking about varying the speed, this can be done with an induction motor, but I believe it is limited. If I'm not mistaken, the "AC50" motor in the OP's project is an induction motor, and he is expecting regeneration braking.

There are also AC motors with permanent magnets in them. They are either called synchronous motors (because they don't slip like induction motors do) or BLDC (brushless DC) motors. Despite the reference to "DC" in the name, they are wound with poly-phase stators so that the electronic drive can control their direction with alternating phase rotation, like any other AC drive. I don't know if these are available or affordable for homebuilt EV projects yet, but they are in the Prius and the in-wheel motors that GregLocock has mentioned (or perhaps more correctly "Electronically commutated").

STF

RE: Electric Car Conversion

(OP)
Sorry for double- posting the link to the video...should read what I wrote a few months ago I guess!

Excited- batteries just arrived!

The motor is indeed a brushless 3 phase induction motor with a quadrature encoder on it which apparently helps the controller greatly with low speed regulation, though it's also used to limit maximum speed of the motor. Here are a couple links:

http://hpevs.com/catalog-ac-50.htm

http://hpevs.com/Site/power_graphs/imperial/peak/p...

The motor is paired with a Curtis controller:

http://curtisinstruments.com/index.cfm?fuseaction=...

The motor is open drip proof, i.e. internally fan ventilated rather than TEFC. That helps it develop the short term peak power it needs, without frying, while also being lighter weight and less bulky. Service life on these is reported to be excellent, properly protected by a properly programmed controller of course.

RE: Electric Car Conversion

SparWeb - what you are describing sounds like a brush-type synchronous motor which is not variable speed capable via the rotor current. You can also get wound rotor and universal motors which run on AC.

That motor and drive should control well pretty much right down to zero speed. Regenerative braking really doesn't recover much energy at very slow speeds so using the brakes vs regenerative braking when close to zero speed wouldn't make any significant difference in the battery life.

RE: Electric Car Conversion

If DC controllers don't allow regeneritive breaking, it's not because the motors won't. It's because the controllers can't. Buy better DC controllers.

RE: Electric Car Conversion

(OP)
The estimated range boost from regen braking, unless you live in hilly country which I don't, is about 10%. Not insignificant with the cost of cells, and almost enough to pay for the small cost difference between an AC and a DC system. You get the benefits of no brush maintenance and no carbon buildup/cleaning for free. I'll also get the benefit of additional rear braking capacity which the car needs anyway (in dry weather at least), and reduced brake maintenance. On the Prius, the brakes went twice as many km between replacements as on my previous cars due to the benefit of regen braking.

The motors usually used in DIY vehicle applications are used DC forklift motors- series wound- that the users have advanced/rotated the brushes on so they can run at higher speeds. The DC vehicle motors are pretty much the same, but with some of the work done for you and with a bit of extra reliability over an over-volted forklift motor. With series wound, regenerative braking is possible but not easy. The DC controllers which do DC regeneration are a little sketchy from the perspective of the DIY conversion community if I've taken their pulse correctly, whereas with AC it's pretty easy.

RE: Electric Car Conversion

I worked on the first Elevated Light Rapid Transit system in Vancouver BC. I spent a few weeks on platforms while the initial run testing was done. The regen braking on the linear induction motors would slow each train from about 50 MPH almost to a stop as it came into a station. You could tell by the sound when the regen braking cut off. You could hear the brakes apply. The brakes typically brought the cars to an easy stop in about five feet.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

"Correct me if I'm wrong..." smile Yeah I didn't think of universal motors - they certainly can be reversed and speed-controlled, but not in the same way as the AC induction motor control/regen/reverse that we were talking about before. I guess they aren't so different from a series-wound DC motor either.
It's interesting that you bring it up because there is no real size limit in universal motors - they've even been used in electric trains, so technically universal motors have been used in EV's already. Not in those nifty linear-induction drive trains that Vancouver's got, though! (I rode that train every day for a week during the Olympics).

STF

RE: Electric Car Conversion

There are substations along the line where AC is rectified. The DC is fed to two bus bars running alongside the rails. The cars/trains pick up the DC and invert it into three phase AC to feed the Linear Induction Motors or LIMs.
The LIMs regenerate and the recovered power is fed back into the DC bus bars. Usually the total power used is more than the total power regenerated. There may be infrequent times when the regenerated power exceeds the total power used. If the bus voltage rises too high, resistor banks are switched in at the sub stations to waste the excess power.
This has to rate as one of the world's largest VFDs with one of the physically longest DC buses.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

Yes, regenerating can help extend battery life, but not by regenerating while your speed is very low. The energy available for recovery is proportional to the velocity squared, so traveling near zero speed doesn't have much energy to recover. Compared to 2km/h, increasing speed to 10km/h gives you 25 times the energy to recover and increasing to 25km/h gives you 156 times the energy to recover.

I do agree that the AC induction motor has advantages compared to a DC motor that make it worth the extra cost.

RE: Electric Car Conversion

I wanted to learn more about regen braking, too, and got out a book that I'd recommend: Austin Hughes, Electric Motors and Drives. Somewhere between layman's guide and textbook - has enough math to improve the explanations, not enough math that a layperson couldn't skip it and understand anyway.

When seeking regenerative braking, on either an AC or a DC motor drive system, the motor can probably do it, whether DC series wound, AC induction, AC synchronous or any similar type. It's the drive electronics that must be capable of the necessary switching/frequency adjustments, and be able to direct the reversed current to the batteries under some control (because some batteries cannot accept recharging at the same rate they give it out, less of a concern with Lithiums). The neat thing is that the drive can switch to regeneration mode without changing the speed of the motor immediately. The controllers are different but the effect may appear the same to the driver of the vehicle. The AC motor torque will reduce immediately when the AC drive frequency is changed, but as long as the frequency control stays ahead of the vehicle driver's input and the deceleration under the car's inertia, then the response can follow the driver's inputs with gradual changes in speed not abrupt ones. On the other hand, the DC drive only needs to switch the polarity of the motor's field coil and (again) without changing speed it has already entered regeneration mode. When the applied voltage is reduced now, the current is induced to the supply, which recharges the batteries. So, clearly in both cases, regeneration can be available as soon as deceleration is requested by the vehicle driver, at any speed. The high kinetic energy of the vehicle's inertia at high speed can be regenerated, as long as the controller and the batteries can handle the current. Otherwise the energy might have to be dissipated by a resistor or something equivalent (can't see anything like that in the Curtis datasheet though, so maybe I've guessed wrong about this).

As a side note, I see that a DC drive varies voltage as a PWM of the battery supply (knew that) but the AC drive must vary the AC voltage in proportion to the frequency as it changes the speed of the motor. That's news to me and very interesting. Must read more!

Seems like an EV can't rely entirely on regeneration for its braking. Not at slow speed, as LH pointed out, but also just as a safety measure - what if the controller fails while rolling? Looks like MoltenMetal has re-done his entire mechanical brake system and the lines, so he should be good to go. What percent of the kinetic energy can be recovered in a typical braking action?

STF

RE: Electric Car Conversion

If you want a generator to switch from motoring to g=charging you don't reverse the polarity. You increase the terminal voltage. Increasing speed or increasing field strength are some ways to do this.
Reducing the supplied voltage below the back EMF is another way to regenerate.When a DC machine is running there is only a couple of Volts or a couple of RPM difference between motoring and generating.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

Thanks Bill, that's better.

STF

RE: Electric Car Conversion

"What percent of the kinetic energy can be recovered in a typical braking action?"

perhaps 50% in a typical 0.3g stop from 30 mph, depending on about 10 different things, the most important of which is how much friction braking you are using. A google search is not especially productive, the definitive studies are paywalled.

http://www.ecrostech.com/prius/QandA/Brake.htm is useful, graham davies is a very cluey guy

Cheers

Greg Locock


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RE: Electric Car Conversion

(OP)
The figure of 10% range increase due to regeneration is based on measurements, which are particularly easily made on the Prius as it tracks how many watt-hours of regeneration are done every 5 minutes. What surprises me most about the Prius is how much the Atkinson Cycle and other tricks they use actually improves fuel economy, since the regenerative braking itself only amounts to around 10% of the energy expended moving the vehicle forward, yet the real-world fuel economy improvement of a Prius relative to a similar but non-hybrid vehicle is way more than 10%- in fact it's more than 30%, based on my own measurements after nearly 200,000 km on vehicles of both types driven mostly on the same commute, rather than just comparing EPA fuel economy figures.

I've definitely put some focus on repairing the brakes- no point in being able to accelerate quick if you can't decelerate quick! My brakes on the Spitfire are all direct hydraulic without assist, and I've already put a lot of effort into repairing/restoring them. New lines and hoses throughout already, and it'll have freshly machined or new rotors and properly adjusted rear drums before it goes on the road. Surprisingly, everything in the hydraulic system has been pristine inside so far- nothing rusted or badly seized- but fittings in some cases have been very reluctant to come out. Have had to resort to the wonderful Ridgid long rip stud extractor set more than once, and it's usually successful after the fitting or bolt has snapped off and the resulting cursing has died down. If you haven't seen these before and are still trying to use those useless "easy outs", throw those away and buy one of these sets- worth their weight in gold actually:

http://www.ebay.com/sch/i.html?_kw=ridgid+10+Screw...

It's a set of drills, drill guides, splined shafts you drive into the hole, and matching splined nuts with double hexes on them so you can use two wrenches for balanced torque. The splines are incredibly tough and strong- don't know what they made them from, but it certainly was clever metallurgy.

RE: Electric Car Conversion

22% isn't actually all that unusual in the rather odd world of solar car racing. The cost roughly doubles with every 2% (ie 10%!) step in efficiency, up to whatever limit your supplier can manage. I think with GaAs 26% is fairly achievable, 30% not. With SiO2 i think the highest I can remember is 24. We certainly used to get some very high 23s when we bought 22s. (Dull job, sorting 1000-2000 cells so that the strings are made of equal efficiency cells).

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

(OP)
Update: batteries received, battery boxes fabricated, and the plate that all the EV electric components will be mounted to is in place. Should start wiring when I get back from my family vacation. Assuming I can get the Miata seats in, the brakes working and I don't fry anything, I should be able to drive this thing around the block in the fall, which was the goal.

RE: Electric Car Conversion

"...the real-world fuel economy improvement of a Prius relative to a similar but non-hybrid vehicle is way more than 10%- in fact it's more than 30%, based on my own measurements after nearly 200,000 km on vehicles of both types driven mostly on the same commute..."

From a different thread: "I have a 2008 Prius base model which has averaged 5.77 L/100 km (40.8 mi/US gal) over 190,000 km, taking all fill-ups and dividing by the odo reading. My current Prius C averages around 4.5 L/100 km (52 mi/US gal) in the summer- worst tank in the worst of the winter was 6.1."

5.77 + 30% = 7.5 (your intent?). 7.5 L/100km is perhaps towards the high end of fuel consumption for similar economy cars. Many of my colleagues are getting more like 6.5 L/100km +/- on their daily commute in similar size and vintage economy cars. Those with VW TDI (turbo diesel) Jetta are in the 5s, easily matching the hybrids. So the 'more than 30%' might be just a bit generous for the dear-departed Prius. 10% is certainly an understatement.

On the other hand, your new Prius C is there, easily.

Fuel economy seems to be improving across the board year-on-year.

RE: Electric Car Conversion

So I have to ask, with a car so efficent how do get things you buy from home depo home?

Never made since to me to drive a car when I have to pay extra to have things delivered to my house.

RE: Electric Car Conversion

(OP)
cranky, I built a sizeable addition to my house pretty much entirely by myself when the only car in the household was a '99 Honda Civic hatchback. I get things home from Home Depot just fine without a truck, thanks. I did have to rent the van for an hour a few times, but I saved far more than that on gas- and most of the time, things came home either in or on top of the Civic- that included a 24" sonotube as well as a 4'x8'x30" tall shrinkwrapped bale of 1" Styrofoam sheets, tons of lumber etc. A hatchback with some compression straps and some imagination is a pretty good hauler. Large orders are delivered free by truck, and they have a little forklift on the back so they can drop the load right where you want it. I had shingles delivered to the roof, drywall delivered by crane to each floor etc. for the same reason- to save sweat and time. I try to select my main car based on the needs of most of my driving rather than my occasional needs.

VE1BLL- I did overestimate that a bit. My '99 5 speed Civic hatchback without A/C did that commute for roughly 7 L/100 km year-round average. 7.5 would be pretty high for the Civic, so that's a little less than 30% improvement with the '08 Prius. But to be fair, the Civic hatchback was a much smaller car- much closer to my Prius C than to the '08 which was a base model, larger, had A/C etc. The C is better than the Civic was by more than 30%, which easily pays off the capital premium of the hybrid versus the ordinary car at current Canadian gas prices. You get the environmental benefits of the lower emissions essentially for free, which in my mind makes it pretty much an obligation rather than a choice. Much harder sell on the Prius base model though- it's a much more expensive car. We bought the '08 Prius when we had two kids in child seats or boosters at the same time- you could do that in the Civic but it was a very tight squeeze especially with only 2 doors. As to the 6.5 L/100 km figure for your friends' performance, I'm not sure how or what they're driving. Most people exceed the EPA mileage estimates by around 20% in real world driving, and I'm no exception. There are morning drives where I manage to get my Prius C to do 3.8 L/100 km which is the EPA combined fuel economy rating for that car, but on average it's closer to 4.5 tank to tank. For comparison the Yaris (Echo in the US I think) with auto transmission is about 5.5 L/100km EPA highway/6.8 city with no combined figure given on Toyota Canada's website- so, a real-world combined economy might be around 7.4 L/100 km (20% more than the mean of city and highway EPA). I'd take the hybrid benefit therefore as at least 30%- certainly a great deal more than 10% which is all you should get from regen braking alone. Yes, fuel economy of all vehicles is improving, and that's great. But people still don't care all that much about it, judging by the size of single-driver vehicles I see day in and day out on my commute.

The electric car project isn't about money for me- if it was, I'd be an idiot. The Spitfire's a totally impractical car- but pretty and really fun to drive, which I think is only going to improve with the conversion. But I'm buying parts retail for the most part, and you'd never think of building a car from retail replacement parts if you cared about money. The batteries will almost, in theory, but never really, pay me back in gas saved if I drive them until they're over 3000 charge/discharge cycles. While there is an environmental angle to this for me for sure, the main driver on this is a learning opportunity for both me and my son, and a chance to rescue a classic car that I fell in love with over 25 years ago.

RE: Electric Car Conversion

Sure a car should be fun from time to time. I on the other hand perfer other projects that require I transport bulky items from 10 ft in length, to materials that weigh up to half a ton.

Renting a vehicle on a weekly basis for me isen't very efficent, in terms of money spent.

RE: Electric Car Conversion

(OP)
Well cranky, a man needs his hobbies, and a vehicle capable of making those happen I guess! Renting weekly would be just as stupid as commuting a long distance in a gas guzzler. Regrettably, insurance for occasional use vehicles is a big rip-off here or else I'd probably have a truck or minivan sitting around somewhere- but my driveway will already be full once the E-Fire is on the road!

RE: Electric Car Conversion

"The Spitfire's a totally impractical car- but pretty and really fun to drive, which I think is only going to improve with the conversion."

I think with an electric motor of reasonable reliability (as compared to the original power plant) it could prove to be a very practical car. But "pretty and fun to drive" are both good reasons for the project too, as is getting your kid out from behind a screen from time to time. Hope you can post some pictures one of these days - good luck and have fun in the meantime, molten.

RE: Electric Car Conversion

It's best to balance you car needs, as fun to drive normally dosen't fit with energy efficent.

A little less efficent, and useful for other things is a balance. But still my PU get above 25 MPG, which isen't bad. But the other PU is 4WD for winter needs, and dosen't get as good of milage.

RE: Electric Car Conversion

(OP)
Front pack and control plate. The device to the left is the charger, to the right is the controller, with my JB in the middle. There's a second 10-cell pack between the rear seats and the trunk, where the old gas tank was, with 2/0 cables running in ENT conduit connecting the two packs, recessed between the frame and the floor pans- nowhere is that wire the low point on the car.

RE: Electric Car Conversion

Great pics, molten. keep em coming!

RE: Electric Car Conversion

(OP)
Update: the EV wiring is done, with the exception of the battery management system alarm boards which go on every cell. Now to re-wire all the 12V on the original car...what a mess! I pulled wires with three or four splices in them- and will basically be building a new wiring harness wire by wire. Fortunately the scope is pretty small- headlights, signal lights, dash instruments and their lights, and the fan- but I also need to rebuild the dash as the plywood delaminated.

To pass a safety here I need a defrost/defog heater, even though it will never be winter driven and it's a convertible, so the plan is a ceramic element out of one of those little fan-driven space heaters to be kludged into the place of the old heater core.

Rear brake bleeders are rusted solid. Suspect I may be spending some quality time with those rear brakes before I can test drive the thing, even after sorting through all that 12V wiring. And the differential, the only bit of Leyland drivetrain left in the car, is leaking oil from both of the wheel shaft oilseals. Fortunately I have a spare which doesn't appear to be leaking, but unfortunately the bolts which connect the rear leaf spring to the differential are underneath my rear battery pack- what used to be the gastank. Fortunately the rea pack is not completely in place yet, so I guess I have to tackle the differential in the next little while too.

RE: Electric Car Conversion

(OP)
The wheels are spinning, and there's not only no gas in the tank, there's no gas tank! The fossil fuel era has ended for the Spitfire!

Yesterday I got clarification on a few wiring issues from the guy I bought most of my parts from- he's been doing conversions and then building his own EVs for over 20 yrs now so he knows his stuff and is very helpful. I also found the programming manual for the controller, which I'd downloaded months ago and forgotten about. The issue was that the controller was set up for the wrong throttle type. Took about 5 minutes to figure out how to set that, and I was up and running!

I opted to use the zinc-in-grease paste on the aluminum + terminals of the batteries and a fluorocarbon grease on the - copper terminals and everywhere else the unplated copper lugs were used. I may buy some Belleville washers or Nordlock washers for the connections later. Right now it has the dreaded split helical spring washers that were supplied with the batteries.

I also commissioned my DC/DC converter and my "fuel gauge" last night- no issues. The BMS was commissioned first and tested and works great. Just the charger yet to test, and the first charge has to be monitored manually with me brooding over the thing with a voltmeter checking it all cell by cell, pulling the low cells up with a 6V charger and dragging the prematurely filled ones down a bit with a headlight to get them to an initial state of balance. The BMS shunts about 2A of charge around the high cells to top off the rest, but the pack has to be pretty close already for it to work.

Now it's full speed ahead on the dash and re-wiring the rat's nest of 12V original car wiring left under the dash. At least all the dead IC engine-related crap has been pulled out so it'll be an easier job.

RE: Electric Car Conversion

Having just spent a whole day re-wiring a horse trailer, I think I know your pain. It's like trailers are built, and then, suddenly, out of the blue, someone gets the idea to put lights on them, so a bunch of welders get out their cutting torches to make holes for all the bits to go. This is the third trailer I've owned like that's like this.

Sounds like the result of careful research on the terminal grease. As for the split washers, well, you know what I think of those already!

STF

RE: Electric Car Conversion

I sympathize. One of my horse trailers needs rewiring. I'm not looking forward to the job.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

(OP)
Phew, if this were only a trailer I'd be delighted... I have a hell of a lot more to rewire than that!

RE: Electric Car Conversion

Maybe a dumb question, but how much do you believe this will increase your electric consumption?

I've reading about numbers that electric car homes consume about 56% more electricity.
I'd just like to know if this is accurite.

RE: Electric Car Conversion

Based on 55kWh/300mi, my mileage would result in 350kWh. If I were a Tier 1 or 2 customer, that would actually double my consumption, but, as it is, we use about 750kwh each month, so it would indeed be almost 50% additional consumption, and at the Tier 4 price of $0.32/kEh, $108.43 additional on my bill. My fuel bill for my Prius would be about $122 per month.

TTFN
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Of course I can. I can do anything. I can do absolutely anything. I'm an expert!

RE: Electric Car Conversion

32 cents a kWh!? I've never seen a cost that high. I pay about 13 cents in Tennessee and it was about 15 when I left California 10 years ago.

RE: Electric Car Conversion

(OP)
Just got my most recent electrical bill cranky so I can give you some idea. We used 1713 kWh in 60 days, which is about 28.6 kWh/d or a little more than 1.1 kW draw on a daily average- a lot higher than I'd like and we're working on reducing that further.

I would be charging once at home, once at the office, about 35 days in that 60 day period- assuming the car isn't broken down or it isn't so hot that I'll melt without A/C. My charging would be off-peak at $0.075/kWh, and I'm expecting about 300 Wh/mile and 40 miles per trip, so about 12 kWh/trip each way, or $0.90 per trip. There's also a "delivery" charge which is pretty complex (part fixed, part related to peak kW draw in the day) plus tax, which will bump that up to perhaps $1.10-$1.20/trip. For reference, my Prius C is costing me $3.50 each way in gas in the summer, ignoring oil changes etc. My charge at work will cost about the same, or maybe slightly more, since although it's not off-peak, we're buying electricity wholesale at industrial rates. So I save what, $4-$5/day? On a straight economic basis, the payback on the electric car versus the Prius C is basically never, mostly because the Prius C is so awesome. Whatever I might save on gas, I'll spend on replacement batteries eventually. But as I said before, this project isn't about that at all.

Two charges per day at home, if I did them both at home, would amount to 35*12*2 = 840 extra kWh per 60 day period, or an increase in my household electrical demand of almost 50%. Note that my charger is very efficient- >93%, and the Wh/mi figures include all losses from the batteries to the wheels. But that's not the whole story either. My trip in the Prius would use 2.7 L of gasoline, or about 0.71 US gal, which has a chemical potential energy of about 93 000 BTU (about 27.5 kWh, not that you could produce anything close to 27.5 kWh of electricity from that much gasoline!). The energy used to refine that gasoline is about another 4.2 kWh with the same caveat, since most of that is fuel gas used as heat rather than electricity used as work. I'm ignoring transport etc. for both gasoline and the electrical grid. On that basis, I'm replacing about 31.7 kWh worth of chemical potential energy with about 12 kWh of electricity to do the same job, i.e. to get me to work.

Our electricity here on average is about 40% fossil (100% gas except for whatever we import), 60% nuclear and renewables, so on that basis I'll be shifting my consumption dramatically away from fossil fuels. Taking public transit would of course take less still, but doubles the amount of time I spend on my commute so isn't really a practical option for me more than perhaps a day per week.

The estimate of refinery efficiency and energy content of gasoline is from this reference, which of course answers a question totally different than the one asked because chemical potential and electrical energy aren't directly comparable.

http://gatewayev.org/how-much-electricity-is-used-...

RE: Electric Car Conversion

"Tier 1 is capped to 187 kWh."

If that's for a month, then it's 24/7 of an average of just 260 watts. That would be just about enough to power up my satellite TV receivers.


@ moltenmetal - I'm enjoying this vicariously. Thank you.

RE: Electric Car Conversion

An old rule of thumb for electric power production from diesel fuel was about 13 KWHr per gallon of diesel fuel. If you can convert the energy content of diesel fuel to the energy content of gasoline you may be able to get a ball park check figure.
buried in the specs of most diesel generators is fuel consumption data including the specific gravity of the test fuel.
(One manufacturer who shall remain nameless, posted 10% better fuel efficiency than any of the competition. Buried in the fine print was the SG of the test fuel. Yup, 10% heavier SG than the competitions test fuel.)

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

(OP)
Greg: by my calcs my weight distribution swill be nearly the same as the original car with a full tank of gas, but that's done on a rough guess of weights of stuff I'm adding versus stuff I've removed. I don't know what the front/back weight distribution was originally- don't even know the real gross weight actually. I have original steel rims, and don't remember the tiresize offhand. Wasn't planning on low rolling resistance tires, at least not from the get-go. Before new tires of any sort go on it I have to find someone to do a reliable alignment for me, and just getting the car driveable to a garage I can trust is going to take a while yet. The previous front end alignment was done by my dad and me with string lines and a tape measure, and tires definitely show excessive wear on the outer edges.

Bill: diesel is about 35-36 MJ/L or about 10 kWh/L or 38 kWh/L chem potential. 13 kWh/L from a diesel generator would put it at a thermo efficiency of 34% which sounds about right.

VE1BLL- you're welcome! I'm having a good time with this too- most of the time. I'm very much a cheapskate at heart so spending the money on the parts nearly killed me, but it's been a blast- think I might like this "spending money" thing a bit, but hopefully it doesn't become a habit! The rust repair sucks though- wish the "donor" was in better shape! All these guys on www.diyelectriccar.com who get nice Arizona, California or New Mexico cars with zero rust are making me pretty jealous.

RE: Electric Car Conversion

It may not matter, but Aluminum rims weigh less than steel rims. I found that out when we ordered a moble transformer, and to reduce the weight they used Aluminum rims, as a measure to reduce the weight to street legal.

Yes Otto cycle engines are not very efficent, and adding the modern conviences like A/C, radio, automatic transmission, heated seats, etc. just adds to the energy consumption.

RE: Electric Car Conversion

(OP)
That's the beauty of using an old car for the conversion- none of that crap to worry about. Steering and braking are 100% manual without assist, so no vacuum pumps or hydraulic pumps to worry about. A/C would be tricky in this car under any circumstances, which will actually be a problem for me in the hottest summer months. But the old car used to leak a hell of a hot of hot air off the engine and rad into the passenger compartment (the tranny cover is a joke on this thing), which would cook me in my own juices on hot days even with the top down. I won't have that to worry about now- nor to warm me in the early spring or late fall...

RE: Electric Car Conversion

(OP)
Just ran some calcs to debunk some of the crap claims made by EV proponents like Elon Musk, who claim that they can drive as far on the energy used to make a gallon of gas as a gasoline car can drive on the gas itself- that claim is out by perhaps an order of magnitude in my opinion. The refinery losses per gallon of gasoline work out to about 0.5 kWh of refinery electricity use averted and perhaps another 1.0 kWh of electrical generation potential from fuel gas used in the refinery, according to my best estimates groundtruthed at least a little. At 300 Wh/mile, that would get me about 5 miles down the road with my EV just on the energy not being used to make a gallon of gasoline for me. That takes distribution losses as a wash between electricity and gasoline, and forgets about production of crude from the ground and distribution of crude to the refinery.

RE: Electric Car Conversion

(OP)
Thanks for the links Greg- amazing what a different person will turn up! The weights and measures page I'd found before but never bookmarked. The guy doing the total teardown of the master cylinder picture by picture will come in handy sometime- the MC seemed fine, and I had the brake pressure differential switch apart and its internals and seals are all good. It was exterior corrosion on all the parts low in the vehicle that was the problem, so the car got a complete new set of cupronickel brake lines and stainless hoses. Should have bought some wheel cylinders though, but can probably get those locally. The bleeders are frozen solid, and one is corroded enough that there's no purchase for a wrench on it even if it were willing to come loose.

RE: Electric Car Conversion

(OP)
Success! The car is nowhere nearly safe, or pretty- that's what I'll be up to this winter! But it rolled right out of the garage and down the street! I put probably 15 km on it just tooling around the neighbourhood- on 25 yr old tires I might add...they have to go, once I have an alignment done. Controller settings are really conservative at the moment, so it ramps current very slowly- but you can almost squawk a tire already shifting between 1st and 2nd, which was the highest gear I managed to use in the neighbourhood.

http://youtu.be/KkOyihRqsJ4

http://youtu.be/_96AYv73IEA

Brakes took a while- rear cylinders and adjusters are aluminum with steel parts, so galvanic corrosion took its toll. But everything holds solid now.

RE: Electric Car Conversion

Almost creepy to see/hear that thing moving so quietly. But very cool, way to go molten. When does the kid get to take it for a spin around an empty parking lot?

RE: Electric Car Conversion

(OP)
You hear a guy down the street rev his huge engine while I'm backing out of the driveway- but a friend of mine listened carefully and described the sound as "Star Trek shuttlecraft"...!

RE: Electric Car Conversion

Then "E" is for "El-Baz" (depending on which 'generation' you watched)

and...

CONGRATULATIONS


Thank you for sharing your awesome project with us.

STF

RE: Electric Car Conversion

(OP)
Update: the car is working marvellously, especially now that I've taken the slack out of my accelerator cable and moved it so it actually pulls the throttle pot to the full open position!

A couple issues to deal with:

1) When you tromp on the accelerator, now you can pull 500+ amps at will- the acceleration is very enjoyable! But the stick shift moves noticeably- the rear transmission mounts are too soft for the job and need some additional stiffening or limit stops

2) At the end of the 2nd charge, I'd put 17 fewer Ah of current into the pack than my Ah meter said I'd taken out of it. Can't really drive the car much until I have it road legal (in the spring) but will see if this measurement problem persists. Suspect the Ah meter had a bit of a hard time with the +400/-100 A current spikes which result from driving the car floored for a block and then taking my foot off the accelerator (triggering 100A of off-pedal regeneration). The pack condition seems perfect. I have a dash-mounted analog ammeter in parallel with the Ah meter (which presumably is a high impedance input so it shouldn't care), and there is about 5 W of leakage out of the pack into various parasitic losses when the car is just sitting there not being driven with the ignition off, so bad measurement of that leakage could be the reason for the mismatch. We'll see if it persists once I'm into more or less steady driving.

So far, so good- the car is a riot to drive!

RE: Electric Car Conversion

And what does SWMBO say now?

RE: Electric Car Conversion

(OP)
She, who I have clearly NOT obeyed (by doing anything other than hauling this car to the wreckers), actually surprised me and came for a ride in it! Her opinion hasn't changed too much- perhaps the full-on hatred has dulled to a mere resentment now that so many of our friends have seen the car and think it's awesome. Who knows, it might grow on her, eventually. Or not. Either way, I'm having a blast with it!

RE: Electric Car Conversion

(OP)
Correction to my calcs previously given: Ontario's electricity grid is only 13% fossil-fired, not 40% (as of 2013- 10.9% gas, 2% coal. So the conversion is reducing the CO2 emissions of the car to about 7.4% of what they were before the conversion- forgetting entirely about the toxic emissions of this old pre-catalytic converter car which are also eliminated. That estimate is a bit high because the nuclear that makes up most of our baseload does represent some carbon emissions associated with uranium mining etc.

RE: Electric Car Conversion

(OP)
Turns out it wasn't the transmission mounts at all- the bolts between the motor and its C face mounting bracket had worked loose- no Loctite on those when they went together. Fixed that problem and the thing is rock solid now! The forward/backward torque between drive and regeneration is tough on those fasteners, and HPEVS didn't make it easy on me either- their cable for the motor internal temperature sensor and the encoder comes out through the front face so you have to mount the bracket with spacers. Right now on the recommendation of the guy I bought the parts from, I have four 1/2" nuts as the spacers on the 7/16" bolts- he's done that numerous times and found it acceptable, but in my opinion it's not good enough long term.

RE: Electric Car Conversion

(OP)
Turns out I had set Peukert's exponent incorrectly- actually I set it correctly to 1.0 and then forgot to "save", so it reverted to the default of 1.25...now I get a much closer match between Ah in and Ah out.

The Ah meter is still not automatically detecting a "full" pack, but it's another setting I have wrong. The BMS is working perfectly and my pack is pretty close to being top balanced after only a few charges.

Regrettably it's getting cold here rapidly and after all those rust repairs the last thing I want to do is expose the car to more salt- so it's off the road for the winter. Quality time again with yet more rust repairs. It appears that the previous owner had done some very skillful and artistic patching of the old body panels in the vulnerable lower portion of the body. Regrettably he very neatly brazed in the repairs, and the braze has resulted in both the adjacent original panel and his repair pieces being rusted to ratsh*t. Hopefully my fluxcore MIG patches will last longer.


RE: Electric Car Conversion

Eventually, you can get enough bondo on the car to make it essentially a composite body?

RE: Electric Car Conversion

(OP)
Well...I'd given serious consideration to simply fibreglassing over the rusty spots, using the rusty panel as a form for a strong fibreglass skin, so the remaining material can just disintegrate entirely behind it and not bother me. Regrettably, the lower edges of the body panels (where my fibreglass would need to "land") are also usually pretty rotten, so if I have to slice and replace those, there's nothing left to form the fibreglass around. By the time I get foam in there and shave it to the correct shape, I can have strips of steel bent and welded in instead. Or at least, that's the theory... The good news is that above a certain "water line", the original panels are all solid and thick enough that even a pathetic welder such as myself has something to weld to. But the back side of these pieces will still be vulnerable to rust. I'm counting on Rust Check cavity wax to keep that at bay...

RE: Electric Car Conversion

Sounds like a labor of love. No wonder the wife is jealous :)

RE: Electric Car Conversion

(OP)
Yeah...a smart person would have just shopped around for a body and frame in better shape with a blown engine etc., but I got this one "for free"...which of course meant that I couldn't really screw anything up. If I had a better car to start with, I would have been worried about wrecking things!

RE: Electric Car Conversion

"but I got this one "for free"...which of course meant that I couldn't really screw anything up."

Except for your life and marriage. I inherited Spitfire 1500 in 1983. It was fun to drive but it consumed many hours in repairs a tuning. Spending all "intimate" that time with it did lead to a sort of emotional attachment (have you seen the movie "Her"?) . When it finally died by throwing a connecting rod through the engine bock, it was somewhat of a relief to get rid of it.

RE: Electric Car Conversion

That surprises me. I'd have thought a spit was so easy to fix properly that it would be robust once done. Admittedly replacing the entire loom with something that uses connectors that aren't made of bent tin is a big job, but it only needs doing once.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?

RE: Electric Car Conversion

(OP)
Greg, I once thought so too. I thought that if my dad and I rebuilt the engine properly, it would hold together just fine and go at least another 100,000 km. Wrong! You couldn't keep the thrust washers on the front main bearing from wearing out prematurely and falling into the pan... with a 4 spd and no overdrive, the old 4 cylinder just wasn't durable- highway speeds were just asking it to spin too fast for its own good. No 5 speed was made for it, and the o/d trannies were hard to come by even back in the early '90s when I might have considered one. To potter around in the country at 80 km/hr, I'm sure it would be OK, but that would be useless to me. Then there was the stupid Stromberg carb, and the Lucas Electric demons lurking behind the dashboard...But it's a lovely shape, on a durable frame, and the suspension is decent.

As an electric conversion candidate, being so simple, it's pretty much a perfect donor- so simple. Once I get the rust repairs done and take care of the oilseals in the differential, it's my hope that I'll have a reasonably reliable daily driver for the summer. Oh I'm sure I'll have the odd thing go wrong, probably some of my own handiwork included. But with the original Leyland engine in there? Forget about it...I see the effort put in by these enthusiasts over at the Triumph Experience and just shake my head in wonder and disbelief. A TR6 might be worth the effort, but a Spitfire?

I do exaggerate a bit about my wife's concern with the project. It seems that she's actually come to peace with the car, though she's not what I'd call enthusiastic about it ever. She's a runner- I most certainly am not a runner- and I spend about as much time on the car at present as she spends on training from her perspective. Everybody needs something to keep them going.

RE: Electric Car Conversion

I would highly recommend you switch to solid core wire with gas shielding if you have the ability with that welder. It's well worth the extra expense.

RE: Electric Car Conversion

(OP)
Been considering that seriously lately. The hard wire machines we have at work are lovely, but they're giant so I can't get any practice on a machine with thin hard wire to see how I'd manage. I would have to buy a small bottle because the rentals would add up too fast otherwise. But then I'd probably want a TIG machine too, requiring its own bottle...where am I going to put all this stuff?

RE: Electric Car Conversion

(OP)
LionelHutz: thanks a lot, you finally pushed me off my hind end today and sent me out to spend $350 including taxes on a bottle of 75%Ar/25%CO2 and a hose/regulator/flowmeter set for my MIG machine. Considering the machine itself (a Lincoln MIG Pak 15) was only $500 if I recall, this was a big additional spend- hope it generates good results! Hmm, learned today that hard wire MIG and flux core are reverse polarity from one another. Never noticed- had to check my machine to see if it was properly set up for what I was doing and indeed it was...

RE: Electric Car Conversion

(OP)
Wow, why did I suffer trying to weld thin stuff with fluxcore all this time? Obviously way too cheap for my own good...

RE: Electric Car Conversion

I was taught to weld with an acetylene gas set. So I bought one and struggled for years, overheating parts, ugly blobs, I made every mistake.
Then I worked at a shop that had a TIG welding and it was easier than gas welding. Did a number of projects on the TIG at work. Still, the work was slow and I was constantly fussing with the settings on the unit, which made the work even slower.
Then I tried MIG welding. 5 seconds later I was convinced. I bought a new MIG welding set and I have enjoyed welding ever since. Miller 180

STF

RE: Electric Car Conversion

(OP)
I love TIG but not for tasks like this- one day I'll splash out on a combined TIG/plasma machine and yet another bottle...the hardwire MIG with 0.025" wire is awesome for this sheetmetal work!

RE: Electric Car Conversion

My hobby car has a fiberglass skin, so the only stuff I'm welding is suspension and structural.
My welds using a cheap Harbor Freight fluxcore welder are beginning to look pretty decent.

For the critical stuff, I am only tacking things together. I'm kind of planning to have a real welder go over it prior to commissioning.

It would certainly be nice to have a better rig. For now, like much of my car, it is "good enough".

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

(OP)
Update: I'm still struggling with bodywork. Very pleased with the way my lower body panel patches have cleaned up once the filler was applied and sanded- shapes aren't perfect but better than I'd hoped. I was actually re-patching areas that had been cut out and patched by a previous owner so it was hard to get a reference shape to start from.

The main struggle is with the hood (bonnet, I guess!), which is half the car on this thing from a visual perspective. From the time I bought the car it was a mess- wavy rather than dented, well beyond my skills to straighten in the metal itself. It's such a big, awkward panel that the option of taking it to someone (what I did when I bought the car) isn't really practical this time around- and all he did is flatten it with filler anyway. So I've been learning how to flatten a panel with filler and block sanding, with the block being used more like a plane. And I totally lack the patience to do this well!

The rest of the car has filler in random places, so the option of going down to bare steel isn't an appealing one. That means a lot of sanding out knicks and scratches in the finish- tons of them, all over the place. Then it's on to high build primer and blocking that...I keep telling myself I'm nearly there.

I managed to get short-hair fibreglass or brushable seam sealant on all the holes and seams in my floor pan steelwork, and two coats of rubberized rocker guard on the whole interior of the floor pans, footwells and space behind the seats. It ties things together nicely, and with a coat of primer on it I think that may just serve as my finished surface. Carpet did so much rust damage to the car that I'm reluctant to re-carpet it- any time you forget to put up the soft top and it rains even a bit, that carpet seems to hold the water against the steel until doomsday.

I also remodelled and then fibreglassed the original fibreboard transmission cover to fit the Toyota transmission. I still have some work to do on that- it's a damned awkward business.

I have a plan for the heater, which I am required to pass a safety inspection here. It's a Frankenstein of a little AC ceramic space heater with a 12V 7 blade muffin fan. The ceramic elements are nice in that they are at least a little self-regulating so they're safer than a Ni-Cr wire arrangement like you'd find in a hair dryer etc., but their geometry makes a poor fit with a blower, and a fan like this has a very steep head/flow curve so it's terrible with ducting. Fortunately the 7 blade muffin fan I had laying around generates just enough head to stuff a reasonable amount of air through the frictional loss of the two duct hoses, or so it seemed during my initial test. Space under the dash is awkward and at a premium for sure.

Still hoping to have this thing reasonably pretty and road legal by spring!

RE: Electric Car Conversion

Thanks for the update. Sounds like you're 90% done - just 50% more to go!

STF

RE: Electric Car Conversion

Yeah, congrats on the project.
That will be fun to blast around in. No, of course it doesn't save money - it is for 'fun'.
(sanity maintenance!)
Regarding the summer and keeping cool - the mesh top on mine has worked out super well.
Mine is the mesh from a defunct trampoline, but the 'shade cloth' used for gardens would probably work fine.
It blocks enough of the sun (winter or summer) for comfort, but still lets some air through and you can still see the sky.
So, it's open-air with a bit of protection.

Boy, that was a rusty sucker. Oh, well - unless you intend to show it, it doesn't have to be perfect.
It just has to be good enough for you.

Regards
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

(OP)
Update: applied, blocked, reapplied, repeat... a whole gallon of urethane primer surface. The thing is still not 100% flat- will not be showroom quality for sure, but I've certainly upped my game in terms of understanding how my HVLP gravity-fed paint gun works! The primer/surface has a very high solids content as you can imagine, and the solvent is mostly t-butylacetate which of course is pretty much absent from the gun cleaner solvents you typically buy. The only way you can get the gun clean is by totally disassembling it immediately after use and scrubbing everything with the best gun cleaner you can find. Just running gun cleaner through it until it's clear leaves behind a ton of debris. I also had crappy mixing cups- too low and fat to be accurate- and the cure is MUCH thinner than the resin, so if you're too light on the cure you end up with paint which is too thick for the gun. I have a 2.3 mm needle/orifice gun which should be plenty good enough for this goo (they recommend a 1.8-2.0 mm), but if you mix it even a little light on the cure you end up getting the paint to air ratio too low and it goes on dry and pebbly- with a finish like sandpaper. Fortunately the mix is rather tolerant of imprecise mixing, i.e. unlike an epoxy which must be mixed much closer to right in order to get a fully hard cure.

Gawd I HATE painting and bodywork! It's all good fun in the context of the overall project, but I sure as hell will NOT take up auto restoration as a hobby when I retire...you need a totally different temperament than mine to make that any fun!

Today I'll pick up my quart of tinted primer/surfacer and my precious 2 quarts of expensive single stage solid colour urethane finish coat material. The colour is topaz orange- which brought howls of delight from my orange-obsessed son and partner in the project, and "eww- it looks like puke!" from my beloved wife...still not very supportive, the dear! It's a real '70s car colour- pretty lurid, highly visible, and definitely not red. Given that probably 80% of the Spits still on the road are some shade of red to the point of it being pretty much a cliche, and that I already have two red cars AND a red brick house, repainting it the original "pimento" orangey red was not really an option!

Despite my experience now with a whole gallon of paint through a HVLP gun, I'll never be a painter for the same reason as I'll never be a welder- you need better depth perception and hand-eye coordination than I've got to have a hope of being good at it. So I'll try my best to paint it, let it cure hard, then colour sand and polish it in the spring when I can do that outdoors. There's bound to be a lot of flaws when I'm done, and I'll probably scratch something reassembling it all in the confined space of my shop, so that tedious job can be put off until I really need to do it!

RE: Electric Car Conversion

I know it's too late, but you might have found Endura a bit easier to use. Just a bit easier, though. Isocyanates are nasty on things like gloves and mixing cups but regular gun wash gets the gun clean faster. I've never had "debris" in the gun from the paint I'm shooting.

...the lawyer looking over my shoulder would like to point out that Endura is good for auto body projects like yours, and not for aerospace projects, as my "aerospace" handle would imply.

STF

RE: Electric Car Conversion

(OP)
If I ever do one of these again, I'll look up Endura...

The guy who sold me the topcoat also sold me an acrylic-epoxy hybrid tinted primer. We'll see how this stuff sprays and sands. The acrylic-urethane primer surfacer I used (damned autocorrect keeps changing surfacer to surface!) was a bit of a bear to figure out, but now that I am done, I know how to use it! It's a DREAM to sand- easy as can be, never loads up the paper. Goes on thick without sagging too.

The tinted primer is tinted "yellowish", or so it says on the can. I hope it's a decent colour as I'd like to use it over my floor pans and inside the trunk and bonnet lids etc.

RE: Electric Car Conversion

Speaking of 'too late' - for your heaters, a couple of hot air guns might (have been) just the ticket.
Good pressure, and enough volume that they'd probably actually defrost the windshield.
oh, well.

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

(OP)
Assuming the hot air gun has a universal motor which will run on DC, I could still do that- also assuming that I keep it on the "low" setting so the heat output isn't enough to melt the hose that I need to connect the discharge under the dash. But I'm very unlikely to run it either way.

RE: Electric Car Conversion

I can't count the number of times I helped my dad or friends paint their vehicles...painted my Opel GT once (blacked out the back panel, which always collected a lot of oily soot making it look black anyway, added some rocker panel striping). It always comes down to how much time and frustration you want to spend making it look "perfect". A colleague describes it by the distance you have to stand from the car to not notice the defects (a 10 foot paint job takes half the time as a 5 foot paint job). I've come to like my sandy brown car, which color most perfectly matches our local road dust.

RE: Electric Car Conversion

(OP)
A buddy of mine was over on the weekend and was talking about a doing a 50-50 paintjob on his car- one that looks good from fifty feet away at 50 mph...!

Mine will look pretty rough right after spraying, but hopefully after colour sanding and polishing in the spring it will look pretty sharp! Sharper than the car has looked since I've owned it, that's for certain. Here's hoping, anyway- the coloured primer looks pretty good on it already!

RE: Electric Car Conversion

(OP)
Very orange, complete with orange peel...Topaz orange, which is an original Spitfire and TR6 colour but comparatively rare on the cars that are left. But no runs or sags, and only a few bits of nastiness embedded in the finish, so it should wet sand and polish up nicely!

Very glad this bodywork is more or less behind me- from this point onward, parts should be going back onto the car!

RE: Electric Car Conversion

Ooh really looking forward to the completion of this project, now. Looks sweet.

STF

RE: Electric Car Conversion

Looking really good.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

Looks pretty slick.

RE: Electric Car Conversion

(OP)
...and this...

Worried now about polishing it, as that will probably bring out some of my bodywork flaws! And it's orange, so the orange peel is appropriate! And it's pretty uniform- though there are a few places where I got perfect finish, but they're few and far between. Gun settings...still a mystery. It appears that you need to spray this stuff as thin as the mfg recommends (I did- more reducer than 4:1:1 and you might end up with mud cracking), and then lay it on heavy enough for it to flatten itself- which is just ever so much less than it takes for the paint to sag... If it wasn't such a dead ringer for amateur work, I'd leave the orange peel- the gloss is spectacular right now!

RE: Electric Car Conversion

:/ Sounds familiar. It probably doesn't help that it's probably pretty cold where you are, so the thinner is "sticking around" a bit longer?

RE: Electric Car Conversion

(OP)
I actually have the shop pretty warm before I start, and open the windows and turn on my three muffin fans in the window just before I start to spray. It stays warm enough in there, but the viscosity of the material is just that little bit too high to lay flat I guess. I played around with the air pressure and the fan width and got it a little better, but if the damned stuff wasn't toxic as hell and $100 a quart I would have just got myself a plate of steel and practice sprayed a gun's worth. I was planning on colour sanding anyway so I could have painted it with a roller...

RE: Electric Car Conversion

(OP)
Update: car is DONE, or at least done enough that I'll take it soon for a safety inspection. Assuming the guy is reasonable with me, and I can find an insurer who isn't scared off, it should be legally on the road in the next month or so.

RE: Electric Car Conversion

You have arrived in style!

auto

STF

RE: Electric Car Conversion

(OP)
So SparWeb- you're up! When do you start your MG conversion?! Get on it! Time's a-wasting! And you won't regret it- especially if you chop up a Chevy Volt pack from a wrecker- cheapest Ah available for a vehicle application, if you can get your hands on them! Wish I'd managed it...but the prismatic LiFePO4 cells I used are very easy to package and to handle- just costly.

RE: Electric Car Conversion

(OP)
BTW the motor mounting is now solid as a rock- turns out, I had 7/16" NC bolts in 1/2" NC blind threaded holes on the motor face...they fit, and you can tighten them a bit, but they don't hold solidly. Replaced with the right bolts and with a solid spacer ring between my motor mounting bracket and the motor face, the stick shift stays put and is nice and solid, smooth, free of vibration etc. Doesn't move a mm whether it's 500+ amps of forward juice or 200 A of regen...The car ROCKS!

RE: Electric Car Conversion

Looks amazing!

Any chance of getting a more detailed set of pictures showing placement and mounting of the battery packs, motors and regenerators?

I hope the inspection goes well, and you might be limited to liability insurance on this road queen. You are definitely going to turn some heads!

RE: Electric Car Conversion

(OP)
Signious: all the details are here, and at the same site there are numerous other Spitfires and perhaps fifty other models of cars which have been converted:

http://www.diyelectriccar.com/forums/showthread.ph...

There are no "regenerators"- the inverter generates DC from the 3 phase AC motor to recharge the batteries whenever you take your foot off the accelerator. Totally seamless drive-by-wire. You can also use a pot on your mechanical brake pressure or your brake pedal position to adjust how much regeneration you have.

RE: Electric Car Conversion

MM:

Quote:

...When do you start your MG conversion?! Get on it!
The new garage/shop comes first, and will begin this year.

And... there's this MGB just sitting in the garage of a guy I know... Totally stripped and body already patched... He hasn't touched it in 10 years... It would be a shame not to, right?

STF

RE: Electric Car Conversion

(OP)
Jay- we need more, and better pics of that car!

SparWeb: yes, the garage comes first, but the car comes immediately AFTER! My garage/shop has been in service for about 8 years and paid for itself building my custom kitchen and bathroom cabinetry. Regrettably there was usually an old wrecky car in the way, making me wonder why I was keeping it. I think now that it was a good decision!

RE: Electric Car Conversion

Do you have any suggestions for how much money to offer someone with an old MGB? Not too generous, not too insulting
The frame is, as I said, stripped and patched, but not re-painted, so it may have developed new rust spots in his garage over the years.
He has the transmission out on a pallet but I've never looked closely to see if it's still in working order.
I would probably get stuck with the engine if I was to buy the frame. Can that be re-sold? I doubt it's in good condition.

He is unmarried, so I am unable to approach the Director of Finance on the matter.

STF

RE: Electric Car Conversion

(OP)
A basket case Spitfire might be $2000. This is a MGB rather than a Midget, so would cost a bit more perhaps, and it sounds like it's not in terrible shape. Never been rusty, or just recently restored? Makes a big difference. $3000? He might find that insulting. But $3000 is all I'd personally pay unless it's assembled and running, or restored assembled and running- but I'm cheap. Then again he may have an emotional attachment to it and then money ceases to have the same value.

I'd way prefer a Spitfire as a donor because unlike the B it has a full frame rather than unibody/semiframe construction. But the B is arguably a nicer car overall.

According to Hagerty/Silver Wheels, they figure a 1972 MGB in #4 (fair condition) is worth about $5-6,000 CDN. A quick web search gave that as the asking price, but a lot of those cars sit and rot on the market for ages and don't sell. Per Hagerty's website: "#4 cars are daily drivers, with flaws visible to the naked eye. The chrome might have pitting or scratches, the windshield might be chipped. Paintwork is imperfect, and perhaps the fender has a minor dent. The interior could have split seams or a cracked dash. No major parts are missing, but the wheels could differ from the originals, or the interior might not be stock. A #4 car can also be a deteriorated restoration. "Fair" is the one word that describes a #4"

RE: Electric Car Conversion

If the MGB's owner is a single guy, go say hello.
Maybe he's ready to pass it along cheap to a new home.
If he's not, stay in touch. He may know of others, or he may think about it and decide to unload it.

As for my car - pics on the website in my sig.
And, I'm pretty easy to find on other sites, by reason of name.

Regards
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

(OP)
Thanks Jay- that looks like a very fun project and satisfying result!

RE: Electric Car Conversion

Nice job, molten!

RE: Electric Car Conversion

(OP)
Up to my elbows in grease at the moment, replacing rear shocks, front shocks and springs, rotors and, greasiest of all, front wheel bearings. Now that I have proof of concept, and am reasonably pleased with the way it looks, it's worth sinking some effort and cash into making this thing drive nicely and last a while!

RE: Electric Car Conversion

(OP)
Update: just drove the car to work today (38 miles) for the first time- can't do that routinely because of insurance, but it was smooth sailing- at a steady 55-60 mph, the car is achieving about 250 Wh/mile on an uninterrupted drive. My design was set at 300 Wh/mile, so I'm nowhere near 70% depth of discharge- I have plenty of pack left by the time I get to work. It was a cold morning- only 7 C - and with the top and windows down, it was a chilly drive! Tonight will be more of a test, driving a good chunk of the way in stop and go traffic, but at least it will be warmer!

RE: Electric Car Conversion

It's been six days....
Are you still pushing it back home?

STF

RE: Electric Car Conversion

(OP)
Ha! After a day showing it off to co-workers and taking people for quick rides, I charged it fully just to be sure. The drive home was the most enjoyable trip in Toronto's notorious stop and go highway traffic that I've ever spent! Because the speed was lower, my consumption out of the battery dropped to 220 Wh/mile, nice warm sunshine...and silent at every stop!

Now I'm worried that some evil Leyland demon has managed to survive the restoration and is waiting to jump out and get me. I had the car up on axle stands again and checked all the U joints etc.- everything is fine. I do need heavier front springs because my ride height is still too low at the front, but otherwise the car is running like a champ.

I did a few more calcs, for those interested in the efficiency and GHG emissions. Sources of information are in {}

Ontario power grid: 9.24% natural gas, balance nuclear and renewables. Zero coal. That's a year round average- spring through fall is better at 7.85% fossil. {IESO Mar 2014-Mar 2015}. CO2 emissions are 40 g per kWh at 9.2% nat gas {Gridwatch}

Efficiency chain, power plant to stored energy available from battery: 82%
(6% grid loss {IESO}, which is only charged for at 3.6% of delivered kWh {Toronto Hydro} x 93% charger efficiency {ElCon, verified by my kill-a-watt and ammeter} x 94% battery efficiency {thousands of measurements by Darren Sims, P. E., on his own LiFePO4 pack in his converted Jetta- this is the average in my temperature range}

Conventional gasoline efficiency chain: 81.4% well to tank on an equal BTU basis (I'll call this EBB), treating a BTU thermal as equal to a BTU electric when used in production (98% production, 84.5% refining, 98.4% distribution/transport {all from the GM/Argonne well to wheels (WTW) study 2001} 99.86% evaporation ie. 0.14 % uncaptured evaporative losses at all points in distribution{Env Canada}. Compare with European estimate of 82% {EU JRC WTW Study 2014}

2583 g CO2 per U.S. Gal from above losses {GM/ANL WTW 2001}. 8887 g CO2 emitted per gal by combustion only {USEPA/USDOT Joint figure, groundtruthed by calc using C8H18}. CO2 equivalent efficiency well to gas tank is therefore really only 77.5%- I'll call this an equal CO2 basis efficiency or ECB

100 km trip basis:

Original Spitfire- 8L/100 km {EPA- I got worse because I drove it fast, burning up both gasoline AND main bearing thrust washers...}, 24.3 kg CO2 WTW, 253 MJ energy from tank 312 MJ WTW EBB, 327 MJ ECB

Prius C: 4.5 L/100 km summer {my measurements}, 13.6 kg CO2 WTW, 142 MJ from tank, 175 MJ EBB, 184 MJ ECB

E-Fire: 250 battery Wh/mile (my measurements), 0.76 kg CO2 plant to wheels, 55.9 MJ from battery, 68 MJ plant to wheels

The E-Fire reduces CO2 emissions by 96.9% relative to pre conversion and by 94.5% relative to my awesome Prius C hybrid. It produces negligible toxic emissions relative to either.

It uses 21% of the source energy (ECB) of the preconversion car and 37% of the ECB source energy of the Prius C.

Assuming one daily on peak charge at work and one at home off peak at night, including all fees and taxes, cost of electricity is $0.19/kWh - yes, those renewable FIT contracts are costing us on our hydro bills... Including all losses that's $3.66/100 km. At last fill up price of $1.14/L including taxes, gasoline would be $9.12 for preconversion and $5.13 for the Prius C, both per 100 km. prices here hit an all time peak of about $1.40/L for comparison.

Battery replacement loses the day for the conversion though, on a purely financial basis. My 18.5 kWh LiFePO4 pack cost $8000 CDN and will last 3000 cycles at 70% DOD if Sinopoly's data sheet is to be believed. Even assuming full distance (83 km at 70% DOD) between charges, that's $3.20 per 100 km, all paid up front. Payback against the preconversion car is very long, and against the Prius C is never. Put a $150 / tonne carbon tax on gasoline though and now we're talking- that would add $3.53/100 km to the original car's consumption. It also gets cheaper if you get a Chevy Volt pack for the reported replacement price of $3,000 (presumably subsidized by GM) for 16 kWh of stored energy- or one out of a wreck for $2,0000. But still not an economic slam dunk- until a substantial carbon tax feeds a cost back to using gasoline. Until then, gasoline remains king.

Much is made of embodied energy in these analyses, but in this case you've got to consider that I reused a car which was otherwise ready for the scrapyard- that's bound to have more internal energy associated with it than my battery pack does.

RE: Electric Car Conversion

(OP)
Thanks Greg- at highway speeds I'm closer to 250 Wh/mile, with the top down and all the associated drag. It drops lower in stop and go traffic because I have regen and speeds are lower, which is why I managed 220 Wh/mile on the return trip. On city streets it's higher than 250 Wh/mile because it is impossible to resist that lovely feeling of being pushed back in your seat by all that on-demand torque!

Right now I have only off-pedal regen, set at a peak of 100 A (the controller can do 200 A of regen vs 500 A of forward current). Training myself to drive it right isn't easy- when you want to coast, you need to watch the ammeter and back off the accelerator until you null the current- or put your foot on the clutch. Neither is automatic to me as a driving instinct. What I may eventually do is to map another pedal over the brake pedal with a brake pot to control regen, or to put a brake pot on the linkage slop in my brake pedal (adding some heavier springs to the pedal to give at least some feedback as you're applying the brake). Others have used hand controls but I want both hands on the wheel when I'm braking! Once I learn to drive it better, my stop and go Wh performance should improve quite a bit.

Merging or crossing several lanes on a major highway to a left exit, absent all the mod cons and safety features, is positively terrifying in such a small car! I used to think nothing of it- I drove this car on highways with no concerns at all, but now I'm older and wiser I guess! I get more comfortable the more I drive it, so it's gradually transitioning from terror to thrill. On city streets, it's a positive joy!

I did put spacers under the spring/shock assemblies after the new spring/shock combinations lowered my ride height, but the 1/2" of spacers I added are the most I can manage without drilling out and replacing the three little 1/4-28 studs which hold the spring cap to the spring mount on the frame. I'd been hoping the spring/shock replacement would INCREASE my ride height a bit! I complained to the local parts guy I bought the stuff from and he's looking for heavier replacement springs, but knowing him, he's not looking too hard. I'll have to do the research- there must be a GT6 spring which will fit and which suited the heavier 6cyl engine, so that would be my first choice. I do seem to have sufficient suspension travel, at least when I'm driving- when I'm cornering tight to park etc. there's still a risk of rubbing the tires on the outer lip of the fenders if I turn too tight. I've rolled them a bit with a ball peen hammer, for the rub points in the forward direction at least. Can't bring myself to do the baseball bat thing...not to mention, we have no baseball bat! I certainly would like a bit more suspension travel too, but the ride height is the bigger issue. Right now it's so low that I have to use an old crank scissor jack under the frame to get enough clearance to get my hydraulic jack under the car!

RE: Electric Car Conversion

Have you considered taking the regen off the throttle and applying it to the brake pedal? That is the system that trolley busses once used (and probably still do). With the foot off the throttle the bus would be coasting. The first part of the brake travel brought in re-gen. Further movement of the brake pedal activated the normal brakes. Bus drivers have told me that when the poles came off the wires, the increase in foot force needed on the brake pedal was much higher.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

(OP)
waross: my plan is to do exactly that. I'll have a pot on the dash which will allow me to adjust the maximum regen achieved by the first bit of pedal travel before the hydraulic brakes are applied, in case I tend to start locking up the rear wheels prematurely during wet weather. Some people use a pressure transmitter on the hydraulic brake pressure, but I like the idea of having full regen before I apply any hydraulic braking. I have about 1/2" of linkage slop before the pedal starts applying force the master cylinder, so if I put some springs on that slop and a pot on the linkage, I should end up with a workable regen braking scheme. If that doesn't give me enough travel to regulate the braking properly, I've seen people put a pedal around the normal brake pedal on its own separate pivot,which serves the same purpose- your foot actuates this pedal first, then when you reach the end of its travel your foot applies force to the normal brake pedal.

RE: Electric Car Conversion

(OP)
Over 700 EV miles and still grinning like a madman! Driving the Spitfire on the highway has gone from terrifying to exhilarating! Still a mismatch between my Ah in and Ah out, with the Ah out being about 10-15% more than the Ah in recorded during charging- working with the TBS guys who supplied my Ah gauge to figure out why, but at least the error is conservative, predicting my pack will be empty sooner than it actually is, like having a reserve gallon in your tank when it shows empty.

RE: Electric Car Conversion

(OP)
Hey, I never thought of that! Maybe I'm tapping into the zero point energy of vacuum space without knowing it! That HAS to be it! I'm rich! I'm rich!

RE: Electric Car Conversion

Driving an EV is like driving downhill, there and back.

STF

RE: Electric Car Conversion

Zero point energy...sheesh, get real. Clearly you are getting cold fusion on the platinum electodes in the batteries.

RE: Electric Car Conversion

(OP)
Fortunately, it appears that TBS's algorithm for setting the charge efficiency factor went haywire during an early charge. Setting that parameter to 100% now has Ah in matching Ah out within about 1%. So this vehicle again obeys the laws of thermodynamics!

RE: Electric Car Conversion

Sounds like a lot of fun - congrats!
The regen at throttle lift sounds like the effect of a big gas engine when you lift - compression braking.
(in terms of feel) If you want to coast with a big motor, you'd probably clutch.
cheers
Jay

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

I am starting my project next month - similar kind of thing! Moltenmetal, could we perhaps have a Skype sometime regarding some burning question I have? I would greatly appreciate that!

RE: Electric Car Conversion

(OP)
Hi Starmart: sounds exciting! Suggest you have a look at www.diyelectriccar.com where you can send me a private message (my handle is the same there).

RE: Electric Car Conversion

(OP)
Painted the inside of the hood and trunk lid, finally, and did a few touch-ups on the weekend in advance of my first show. I've ordered some GT6 springs to get my front ride height back up to comfortable, but those will take a while.

Did some big kid show and tell last Friday- I took the car into my son's gr. 7 science class and did a little talk on forms of energy, the history of engines, energy efficiency, and where the electric car fits into all of this. The kid figures that about 25% of the class was really interested, but when I got to the show and tell part I think I had way more than 25% interest for sure! I think I'll be doing a few more of those show and tell sessions next school year.

Also finally got around to playing with the Curtis controller's settings, and discovered that although my throttle pot lever was being cycled through its full range of motion, or nearly so, by the accelerator cable, it was not actually adjusting the input voltage beyond 2.6 V at full throttle- and the input was spanned for 0-5 V. Fixed that by re-spanning the input in the software...wow, the car really was fun BEFORE I did that, and now it's positively breathtaking! I also adjusted the acceleration parameter by a very small amount beyond the factory default- any more and I'd be squawking the tires when I didn't want to. I also upped the off-pedal regen current, but I'm doing that in small steps until I get around to installing a regen pedal with a pot on the dash to limit the maximum regen current- otherwise, instincts being what they are, the tendency to pop your foot off the accelerator will be too strong and might get me in trouble in wet weather. Regrettably the standard settings don't allow for a pot input to set off-pedal regen current limit, and the one-button programming using the Curtis Spyglass display is functional but not what you'd call convenient. The settings do allow for an "econo" mode switch, so that might be a way to "cheat" it to do what I want. Doubt I'll get around to the regen pedal until the winter.

RE: Electric Car Conversion

How about leaving the 'gas' pedal alone, and linking the regen to an overlay on the brake pedal?

Said overlay comprising, say, a carbon pile resistor surrounded by a mechanical stop, such that the first 1/2" or so of brake pedal travel, normally clearance and working just against the pedal return spring, would bring in the regen, and then the normal service brakes would apply?

That might make the car less intimidating for drivers who are not expecting anything weird. (My friend Mark rigged his otherwise traditional kart so that you had to push down on the gas pedal to close the throttle; it was counterintuitive, and scary.)

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

You know you're cool when your teenager isn't ashamed to be seen with you around his classmates. Did you give the tykes a taste of that accelerator kick?

STF

RE: Electric Car Conversion

(OP)
That's my ultimate plan Mike, but with a pot on the dash to allow you to set just how much regen you get at full brake pedal slack travel, just prior to the mechanical brakes going on. Regrettably, the ordinary programming doesn't allow a small amount of off-pedal neutral braking with supplemental brake assist from the additional brake potentiometer- there is no combination of off-pedal and pedal-driven regen permitted as a valid "brake type". Having a small amount of off-pedal regen rather than a pure "coast" when you take your foot off the accelerator, which is the way the Prius is programmed, tends to give the driver a feel very similar to what you get with a gas engine car. Having zero "off pedal" regen can feel a little unnerving at first, as can having a heavy off-pedal regen setting. The latter is actually dangerous in a RWD car in wet weather because you risk locking up the rear wheels.

RE: Electric Car Conversion

(OP)
Yes, but as it turns out, only at 60% of throttle...could have been even more impressive!

RE: Electric Car Conversion

in concept, to keep uniform braking on all fours, it would be nice to modulate rear brake pressure so that brake+regen never takes a bigger percent of available traction than braking alone on the nose?
(yes, a non-trivial effort)

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

(OP)
With front discs and rear drums, on dry pavement I can already tolerate quite a lot more rear braking than I have. As best I can tell, I can lock all four wheels right now and the thing stays stable and true under hard braking. I just think it will be safer to dial back the regen during wet weather. After all that rust restoration, driving in wet weather isn't exactly on my list of fun things to do with this car anyway! Basically I'm driving it to work every nice day where there's no rain in the forecast- doing that will keep me within the km limits of my insurance. But I did prove the car in heavy rain, driving back from downtown through one of Toronto's legendary "bomb" thunderstorms. There was quite a bit of ponding on the road- the car had to plow water out of the way. After the storm subsided I lifted the hood and all my electric components on my controls mounting plate were dry- still had dust on them! The front of the battery pack probably got a bit wet but that's no problem. Can't say that for the passenger compartment though- there are a few more holes in the firewall that need sealing, though I'm not sure where they are. My floor pans were water tight also- and it gave me good indication of where I could drill the drain holes for best effect. No carpets in the car now or ever onward- they hold the water in and drive the rot.

RE: Electric Car Conversion

I can not see any good technical reason to want "off-pedal braking". It may recreate what you are familiar with, where engine friction slows the car. But that is inefficient, unnecessary,and often undesirable. Most cars now have overdrive to improve fuel economy, which let's the car coast without back-driving the engine. If you want to slow down, that is what brakes are for.
Rear wheels have maybe 20% of the stopping power of front wheels. You need to take that into account when tuning the brakes, whether revenue or mechanical, or else you will frequently be locking the rear wheels.

RE: Electric Car Conversion

Actually overdrive is a higher gear ratio and does back drive the engine. Look at the tach while coasting in overdrive and then shift into neutral and look at the tach.
Allowing a car to coast was a feature know as freewheeling. That last car I saw with free wheeling was a 1948 Rover. The feel of freewheeling was so counter intuitive that it was almost never engaged. Travel was a series of coast and accelerate cycles. A very unnatural feeling.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

The three cylinder two stroke Saabs had selectable freewheeling.
I suspect it was included to make them less dangerous in snow.
Having the center of applied engine braking between the two front tires, and the CG several feet behind that, can snap yaw the car 180 deg in the time it takes to release the throttle and move your foot to the brake pedal.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
The off-pedal regen gives an efficiency hit for sure, just because getting good efficiency out of that arrangement requires a recalibration of basic driving instincts- you need to watch the ammeter which is not second nature. But zero off pedal regen feels very strange- I'm sure I'd get used to it, but off the bat it's a bit startling. Not that I'm likely to let too many people drive my car, but I do want it to "feel" like a regular car so it's not unsafe to "test drive"... With the new throttle and accel settings, the need for a "valet" or "econo" mode setting (which the controller allows) which I can select via a keyswitch, is becoming a wee bit more obvious!

RE: Electric Car Conversion

The engine rpm of my F-350 (automatic) drops to idle speed when I take my foot off the accelerator at highway speed in overdrive. There is nothing "strange feeling" about it. In other gears the engine does not slow down. "Overdrive" is a nebulous term and may not be the correct one, but I do not have a "free-wheel" control except for the one called overdrive. The point is that there is nothing strange or unsafe about a car coasting with no throttle pedal input. It is the ideal in most cases. Have the car noticeably slow when you take your foot off the throttle, for any reason other than braking, is annoying. It is only a artifact of a simpler mechanical design which keeps the engine directly coupled to the wheels at all times. What is strange is trying to replicate this artifact when it adds complexity and is totally unnecessary.
In an electric car the throttle pedal should not be doing any braking.

RE: Electric Car Conversion

very often the car will disengage the converter clutch when the throttle goes to idle.
At cruise speed, lots of vehicles are running the engine slow enough, that a bit of converter slip returns the enging pretty close to idle anyway.
Plus, some transmission gear stages are clutch + sprag, and will overrun unless you manually lock it in a gear.

Jay Maechtlen
http://www.laserpubs.com/techcomm

RE: Electric Car Conversion

I grew up driving in the mountains and have a different perspective and expectation to off throttle engine braking.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

Sticking to city speed limits is easier if there is off-throttle braking. No need to mess around with the brake pedal at all. I drive 30 (mph) limits in 3rd gear in my manual, the engine sits at a sweetish spot and the way it's all governed and calibrated around that operating point, vehicle speed is closely and linearly related to accelerator pedal position.

Steve

RE: Electric Car Conversion

Conversely, a 4G Camaro with automatic idles at 40 mph, so city driving is possible with just the brake pedal.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
Finally free of my "toy car" insurance- the company that quoted me pre-conversion was compelled by their ombudsman to write me a policy!

I can now drive the car legitimately to work or wherever else I want, with a reasonable number of km per year that I am unlikely to exceed. Of course if anyone else comes to them to insure an electric conversion, they have now primed their call centre staff to say "no, no HELL no!". In fact they made it clear that they will not insure another car if I migrate the parts to it. So here's hoping the old Spitty stays in fine form!

230 Wh/mile on the way to work today- now that I have the right springs in it and the front geometry is a bit better. Both sets of springs I got from my parts guy were wrong- the pair I put in was an old "swap meet" pair I had laying around- covered with 25 yrs worth of grime, but once I had them cleaned up it was apparent that they'd never been in a car- still had the paint marks on them to indicate which springs they were.

RE: Electric Car Conversion

(OP)
1600 miles of pure EV bliss so far. Average 236 Wh/mile over that 1600 miles. The only problem to report so far is my brake master cylinder reservoir, which leaked brake fluid because the replacement screws I used to hold it to the MC were too long and bottomed out in their threaded holes before they completely compressed the rubber seals. Regrettably the brake fluid completely ate the paint wherever it went...fortunately none of it got to my long suffered-over bodywork!

RE: Electric Car Conversion

Ugh. Brake fluid.. We used to use it as paint remover in shop..

The shop guys shellacked a guy's car with it because he hit-an-ran a buddy of ours and his girlfriend who was riding with him on a motorcycle. The police just shrugged even when shown the car and the motorcycle paint on it. (high school vigilantism)

Keith Cress
kcress - http://www.flaminsystems.com

RE: Electric Car Conversion

(OP)
Easy fix- the replacement bolts I used to hold the reservoir on to the MC were too long and bottomed out before they got the gaskets fully tight. So they sealed for a bit, then leaked a bit, then a bit more...Problem solved now, until the next time that the evil gunk gets out! I've put a tray of heavy plastic sheeting under the MC and some absorbent pads which should take care of the next spill.

RE: Electric Car Conversion

(OP)
Update: differential failed after just under 2000 miles of otherwise trouble-free driving. Something seems to have broken loose and trapped itself between the crown gear and the housing, punching a neat round hole about the size of a nickel in the rear of the casing, which the crown of course then used to pump all the oil out of the diff in a few seconds. Luckily I noticed the noise on the last few km of my drive home, so it didn't burn out totally and leave me stranded.

Fortunately I have a spare- I was always suspicious that the diff, which is the only major piece of Leyland drivetrain left in the car, would bite me in the rear end (pun intended) at some point! Unfortunately, my plan to put all new oil seals in that spare diff while I had it on the bench will not be possible, as the car and I have a date on Saturday- a buddy of mine is including us in a video he's making. Another few minutes off my 15 minutes of fame allotment in life...

RE: Electric Car Conversion

Ah that sux man! If you haven't opened the pumpkin yet I'd hazard a guess that it was a thrown gear tooth that got pinned. Mayhaps you can hit the diff with more torque with the motor than the engine could ever dish out?

Keith Cress
kcress - http://www.flaminsystems.com

RE: Electric Car Conversion

(OP)
My understanding is that the diff in the Spitfire is the same one that is used in the GT6, which put out as much peak torque as my motor is capable of, within a few foot-pounds- the British high compression engine versions at least. But my diff had leaking oil seals and I probably ran it low of oil at some point- and it was part of the same drivetrain that gave me grief from day one in that car. I'm well shot of it!

The spare diff is in, and runs way quieter than the old one did. We'll see if there's a pool of 80W90 under the car tomorrow morning, but I'm hoping the thing seals well enough to last out the rest of the nice weather.

The old diff fought me every step of the way- it was rust-welded to the bottom of the leaf spring to the point that it took a hammer and cold chisel to free the spring from the diff. Had to remove my rear battery pack- If I had done that right off, I would have saved myself hours of suffering. My Haynes manual led me to believe that the spring retainer construction was different than what is actually in the car, which didn't help much- there were four studs that HAD to come out come hell or high water, and they were not fun to say the least. Positively kicking myself for not swapping in the spare when I had the body off the frame- but I didn't know the pedigree of the old diff so it was too much of a gamble to take one which was known to work and replace it with a potential dunner. Hindsight is of course 20/20!

My son, who turns 13 in a week or so, was a GREAT help- he was with me the whole day, undoing bolts, fetching tools, operating the jack as we tried to get the old diff out and to guide the new one in- he was a constant help. His skills have really come along, and his confidence too. He did a trades-related camp this summer for a week and had a riot- he was showing the other kids what to do. Seeing him come along was worth the price of the car conversion parts!

RE: Electric Car Conversion

Quote:

Seeing him come along was worth the price of the car conversion parts!

And much more!

Keith Cress
kcress - http://www.flaminsystems.com

RE: Electric Car Conversion

(OP)
Great news is that the new diff seems to have good oil seals.

Bad news is that apparently my dad and I didn't fully understand the design of the Leyland driveshaft...when we swapped in the Toyota motor and tranny, we cut the Toyota driveshaft off at the tranny end, keeping its U joint- and we chopped the front U joint off the Leyland driveshaft, machined both pieces in the lathe, fit them together and even welded them in the lathe- perfect. Only one wee problem, or at least it seems that way from what I understand now. The Toyota transmission has a sliding joint between the front U joint and the tranny- a splined collar slides in and out of the transmission to provide some axial "give" in the assembly, which is really handy for giving clearance for work on the drivetrain. But the Leyland driveshaft has an arrangement of flat strips of spring steel between the rear 2-bolt flange of the driveshaft and the front 2-bolt flange of the rear U joint, which I think were intended to serve the same purpose- not much axial give is required in the Spitfire because both the tranny and diff are fixed to the frame with rubber mounts and the rear wheels are independently suspended, and I guess this was a cheap and probably pretty reliable way to provide it.

Each 2-bolt flange bolts to diagonal corners of a square formed by two straps, and there are two layers of straps for a total of eight.



At least one of those spring-steel straps is cracked through and, I hope, that's the source of a new noise I hear whenever I take my foot off the accelerator and the motor goes into regenerative braking.

New straps are on order, from Spitbits in California (my wallet is stinging from the importation charges already), but I'm thinking I should make some thicker ones out of say 1/8" thick mild steel plate and make the assembly more rigid and resistant to the sudden torque reversals. I'd need longer bolts, and would want those pieces to be identical so the assembly stays balanced- but that should be about it. Having the driveshaft free to move axially at both ends is bound to be hard on the U joints over time.

Any thoughts from you folks who have forgotten about cars more than I'll ever know about them?

RE: Electric Car Conversion

Mild steel is not appropriate, and thicker is not better.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
Why not Mike? My idea was to make the joint more rigid in the axial direction, to force the axial movement to happen at the transmission end where there is already a joint designed to handle it. I understand mild steel will be weaker and less springy than what I presume the existing straps to be made of- but if the section thickness is significantly higher, should it not also be stiffer and make the joint stronger?

RE: Electric Car Conversion

Mild steel is much lower strength but more ductile. That means that the strap will yield every time it flexes rather than elastically flex.

RE: Electric Car Conversion

(OP)
The existing straps are very thin- will measure and report back, but they're on the order of say 20 gauge.

My plan is to replace them with straps which are 1/8" thick and wider. The plan is to keep them from yielding OR flexing in the first place, and if they're thick enough it would seem logical that the driveshaft would transmit any axial force to the front end where there's already a sliding joint to take up the movement. In other versions of the Spitfire drivetrain, these rear straps are eliminated in favour of a four-bolt flange on each piece, and there is a sliding joint at the transmission similar to what I have on my Toyota tranny. Trying to replicate that design without having to replace the rear U joint itself and the end of the driveshaft, both of which are in good shape right now.

RE: Electric Car Conversion

(OP)
Straps were 0.030" thick x 3/4" wide and definitely springy. One was completely gone and another cracked through. Replaced all eight with 1/8" thick x 1" wide mild steel ones and longer bolts. Everything is smooth and noise free so far both on hard accelerations and hard regen braking. Hope this fix holds! Having axial play at both ends could allow the shaft to squirm on the two u joints which would be very bad news- my new assembly should force any required axial movement to the tranny end splined joint where it is intended to be.

RE: Electric Car Conversion

Watch the straps for cracks. It should not take very long.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

I could be missing something, but I don't see why there would be any need for (or cause of) significant axial movement at the differential since there is now a spline in the shaft at the transmission. I claim no expertise, it might fail in the next mile, but I cannot see any reason to believe that it will fail prematurely.

RE: Electric Car Conversion

(OP)
I will be keeping a careful watch on this assembly Mike- but perhaps a little insight into why you think the new straps will fail would be more helpful than the ominous warnings!

RE: Electric Car Conversion

They're mild steel, and thick.
Fatigue from cyclic loading will crack them.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

I'm surprised to see this in a Spitfire tranny.
If this was a helicopter, I'd call it a "Kaflex" coupling.
Since the spitfire already has a set of U-joints and a spline, I'm not absolutely certain what the Kaflex joint is in there for, either. Does the body of the car flex so much that later models of car needed extra flex built into the transmission?

Umm, I think it's item #6 on your parts list scan, right? Does that diagram show parts from only one car, or is it two configurations from two different cars, in the same diagram? Is there an intermediate hanger bearing, not shown?

So it must be overlapping metal straps, drilled on the ends, the combination of which in a square makes a coupling between two bolts on one fitting to two bolts on the other fitting. I guess we can ignore, for the moment, there there already are 3 things in your tranny that are supposed to do the same thing as the Kaflex. The fact that the Kaflex is broken is proof, in a strange way, that it was actually doing something. The bars cracked because they were already subjected to excessive misalignment (or maybe the spline's freedom of motion bottoms out?). Replacing the bars with something thicker will change the allowable misalignment and displacement equation. Replacing them with something softer will change the stress equation. Neither in your favour.

STF

RE: Electric Car Conversion

Do i understand this correctly:
Both the transmission and the differential are fixed in place.
Old designs used the plates to allow for slight end play.
New designs use a spline to allow for end play.
You are stuck between old design and new design.
The spline will absorb any end play. The new plates will transmit torque but will not be flexed by end play.

Bill
--------------------
"Why not the best?"
Jimmy Carter

RE: Electric Car Conversion

(OP)
Waross, I think the answer is yes to all your points.

Yes the picture shows two different versions of the same driveshaft from different model year Spitfires. Mine is the one with the square part 6 which consists of eight 0.030" thick spring steel straps stacked up, which connect the 2 bolt flange on the driveshaft to the 2 bolt flange on the differential end u joint. In that design, in the original Spitfire 1500, the flange bolting the front u joint to the transmission is solid, with no splined joint.

The transmission and differential are both bolted to the frame with rubber shock mounts. My electric motor holds the front of the transmission more or less rigid, with very limited rubber slop- I did not reuse the original engine mounts- my motor mount is much more solidly connected to the frame as it doesn't dance around like an IC engine does.

The axial flex provided by the straps was presumably there to compensate for small amounts of axial movement of either part within the perhaps 1/4" of total relative movement in the axial direction afforded by the tranny and diff rubber mounts, plus any frame flex etc. The u joints themselves should take care of axial misalignment- all the straps handle in the Spitfire is any motion requiring the shaft to be a minor amount longer or shorter.

My version of this assembly has a splined joint at the front connection between the transmission and the front u joint, which should accomplish the same thing, only more reliably. A splined joint like that was used both on earlier and later model year Spitfirss.

It seems obvious even to a chemical engineer that you don't want axial flex at both ends of a shaft with two u joints. The tendency for the assembly to squirm like a rubber band being twisted would seem to be a major problem under large torques. You want a thrust bearing at one end of the assembly- in my case that would be the front bearing in the differential, which no doubt wasn't designed for much thrust, but should be able to handle at least some.

So my thicker straps are intended to make the rear joint axially rigid, or at least more rigid than it was. As close to a solid 4 bolt circular flanged joint like the one between the rear u joint and differential as I can manage.

Since there's a splined joint at the front which won't permit the assembly to push on my new straps in the axial direction with a force greater than the friction in that splined joint plus the inertia of the shaft, it's tough for me to see what force would be cycling my new straps to the point of fatigue. I know that a little force through millions of cycles can be enough, and I know they're not made of a springy material, but the material they are made of is greatly thicker so it should be stiffer and should not allow much strain. The stack of straps is about as thick as each two bolt flange at each bolting face, and those flange/yokes aren't made of spring steel either.

I put the initial failure down to the material being forty years old, and the assembly being free to squirm. Obviously we should have eliminated this flex joint when we made the new shortened driveshaft in 1992, but changing it now would be a huge effort. I could be wrong of course- maybe those straps will fatigue, or worse still, the yokes will fatigue. If my new straps don't last long, I will replace them with the set of spring steel replacements I have on order. This is relatively easy to work on and inspect from under the car- and it does seem to get noisy enough as a warning that I'm not worried about a sudden failure. And right now it's silent, which is a good sign.

RE: Electric Car Conversion

If the shaft is installed perfectly straight, with no articulation of the U-joints, the needles in the U-joint cups will run dry locally and fail from surface fatigue or something related.

If the shaft is installed with equal articulation angles at each end, as it should be, and the angles are large enough that the needles' tracks overlap so the needle lubricant circulates, then the U-joints will be okay, but then your straps are subject to tension/compression cyclic load variations just from transmitting torque while the joints articulate and the shaft accelerates and decelerates relative to the ends over every rotation. That load case has nothing to do with axial force. ... and should be mitigated some by the extra cross section.

... but the extra cross section and soft material become problematic when the spline doesn't slide easily under load. Keep it well greased with sturdy stuff.






Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
There is definitely articulation at each end of the shaft, as the face of the diff drive flange is normal to the ground and the transmission's rear axis is close to level and the elevations of the two centres are different. The angles should be close enough to equal. Are they enough? They're pretty close to original so I think so. All the u joints are tight, both on the driveshaft and the two halfshafts. No slop, nor any rust rings on the backs of the cups. Keeping a close eye on those due to their age and the torque.

Will definitely keep that sliding joint lubed!


RE: Electric Car Conversion

We may have stumbled on the root cause of the strap failure.

In a normal automotive installation, the pinion shaft axis is level, and the driveshaft slopes up say 3 degrees going forward, and the engine slopes up another 3 degrees going forward, putting the crank at 6 degrees from horizontal. Actually, the pinion may point down 3 degrees so the driveshaft is level, but the situation is the same; the U-joints have equal angles, and the angles are of the same 'sign'.
In that case, the driveshaft should be 'straight', which means that when you look at the end of the shaft itself, the U-joint yokes on each end of the shaft proper should be parallel. ... just as you see them in the shop manual.

In your new case, the pinion is horizontal, and the 'engine' is horizontal, drive and driven shaft are parallel, so you need a 'crossed' driveshaft, i.e. when viewed from the end, the u-joint yokes attached to the shaft proper should be crossed at 90 degrees to each other. The reason why has to do with the sinusoidal transfer function of a single u-joint. Any competent driveshaft shop should be able to rotate one of your yokes for you.


I went looking on the net for a picture to reinforce my point, and pretty much all of the information out there, especially from the driveshaft experts, especially the stuff with nice illustrations, is completely wrong.

So find a picture of a 'double Cardan' joint. They are typically equipped with a small ball and socket in the center, so that the ends physically can be angulated, but cannot be displaced in a lateral direction and remain parallel. The center 'driveshaft', short as it is, has parallel yokes, as it must for minimal NVH. If you built one with crossed yokes in the center piece, you would be able to move the end shafts radially, but you would need some mechanism to hold them parallel, or the center section would be subject to torques with a large cyclic component, just as yours has been since you removed the gasoline engine and substituted an electric motor with a level axis. Did you notice the slope of the engine's crankshaft?



Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
Within a few degrees I can't tell for sure whether the transmission shaft centreline is dead level or sloped a bit . Similarly I don't know whether the pinion flange is pitched downward a wee bit or dead plumb to the frame. If the transmission is sloped, it may be a degree or two downward from rear toward the motor end, (if I understood you correctly that would be the wrong way) but not much more than that. There is an elevation difference of several inches over the ~3' length of the driveshaft, with the shaft sloping upward from differential pinion flange to transmission output shaft (which sits above the frame) The transmission is at just about the same angle as it was when I had the Toyota engine in the car, but the Triumph engine did sit lower at the front- not sure if the transmission sat substantially lower too. I will have to see a drawing of the original drivetrain geometry to be sure about its original angles.

I didn't realize the geometry was that touchy...!

I was looking at the CV joint wiki a while ago which has a picture of a double Cardan joint. Will need to think about what you've said and look at that little animation to understand it...I do know that a single u joint has a nonconstant velocity, but thought that two joints paired in reverse or out of phase so to speak spat back out a constant velocity. Didn't know that you needed them to be at particular angles relative to one another to work though...

I had this reversed before- your point was that the crankshaft normally slopes upward toward the front of the vehicle. I could raise my motor to make this angle closer to what Mike says it should be, but it would be a lot of work- as would removing and rotating one of the u joint yokes. But bolting the two 2 bolt flanges together without any straps would give me the 90 degree rotation I need too, would it not? I just don't like the hinge point that would be created where they bolt together....



RE: Electric Car Conversion

(OP)


If this drawing is correct, I thought I had the top geometry- or close enough to it.

Mike felt that the middle geometry was likely what the Spitfire had originally (did I get that right Mike?)

I have the bottom geometry- and therefore I guess a problem with cyclic loading on the driveshaft. If I were to bolt the two 2bolt flanges together without straps, the yoke ears fixed to the driveshaft at each end would be aligned, as shown in the Triumph parts drawing and the top picture in the image above- but with the straps in place, the ears are rotated by 90 degrees to one another.

Impressive that the assembly as it stands is actually working without giving me excessive vibration- or maybe i'm just used to vibration...

RE: Electric Car Conversion

(OP)
D'oh...just re read Mike's excellent post for about the fifth time...so the image I posted is apparently incorrect, as the middle geometry has angles of the same sign and the top geometry has angles of opposite sign. So I have a crossed shaft, totally by fluke, which if I understand Mike correctly, is actually what I want in this case- assuming my transmission is more or less level and the pinion shaft is similarly level.

Mike, please correct me if I'm wrong, again...!

RE: Electric Car Conversion

In that illustration, the top image is wrong, the other two are both correct.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
It appears that Mike is right, and this is widely misunderstood! But I think I understand Mike's point, and why the bottom drawing of that figure from a 4x4 site I found, which is as close to my geometry as possible (with the straps in the assembly), is actually correct rather than incorrect. It seems logical that the oscillations would be opposite for a given joint arrangement depending on whether both joints angle in the same direction or in opposite directions from the main shaft- angles of the same sign or opposite signs about the central axis of the shaft to put it the way Mike did. Similarly it seems logical that by arranging the joints at 90 degrees to one another the oscillations would be minimized.

I wonder if someone has a motion model of these somewhere so you can play with the angles and see the results!

I certainly didn't know this, and I'm sure my Dad didn't either. But I'm surprised that he didn't match the orientation that the Spitfire shaft had before we cut it- that he set the yokes 90 degrees apart was a fluke I'm sure. I have no idea what the orientation of the Toyota's shaft was originally.

Mike, even though it appears that blind luck won for me in this case, you deserve more LPS than I can award for clearing this up for me. Thanks a lot!

RE: Electric Car Conversion

I have to completely disagree with the whole drive shaft u-joint conclusion that has been made here. The top two images are correct.

First point, the motion equation of the u-joint uses 1/cos(joint angle) so the sign of the angle doesn't matter, just that the absolute value of the angle at each end is the same.

Now, consider the motion of the U-joint. A U-joint puts 2 cycles of sinusoidal oscillation into the output shaft rotating speed for every rotation the input shaft makes. In other words, for every 90* of input shaft rotation there is a peak or valley in the output shaft rotating speed. So, this means the next u-joint needs to be rotated 90* to put each peak or valley it creates opposite to the peaks or valleys the first joint creates.

Well, the output u-joint is already turned 90* compared to the input u-joint when the drive shaft has both yokes in line.

Besides, I've owned a few vehicles that were produced by the millions and they used the top configuration and they worked fine without any drive shaft vibrations. I've yet to see a drive shaft with the yokes 90* to each other.

There is a reason you think every expert on the internet got it wrong and is showing the wrong info.....

RE: Electric Car Conversion

(OP)
Hmmm...now I'm really confused!

LionelHutz said "Well, the output u-joint is already turned 90* compared to the input u-joint when the drive shaft has both yokes in line."

Is that right? Irrespective of the angles of the joints relative to the driveshaft axis? Damn, I'm having a very hard time getting my head around this moving geometry to understand who is right here! I wish I had a simple double Cardan joint here that I could play with, bending it in the two configurations and spinning it to observe the output shaft rotation!

I have two potential arrangements which are easy to implement:

1) With the u joint yokes on the driveshaft aligned, and the straps eliminated and the two 2-bolt flanges (between the rear u joint yoke and the rear of the driveshaft) bolted to one another. That would give me u joint yokes aligned with one another.

2) The one I have in the car right now, like the Triumph picture but with thicker straps- except the u-joint yokes are definitely at 90 degrees to one another rather than the way the Triumph drawing shows them (aligned).

...and right now I'm not sure which one is best!

The present arrangement doesn't seem to be generating undue vibration, but I might just be used to the vibration it is generating. I did have the thinner, springier, 40 yr old straps fail in this configuration. I put that down to the fact that both ends of the shaft were free to flex axially, which I know to be bad news when using U joints, and to the age/cycle history of the material.

I do find it hard to believe that the original Spitfire engine had a driveshaft angle as steeply inclined toward the rear of the car as what it would need to be to give the squashed U configuration (middle drawing above), and its u joint yokes were definintely aligned. The hood of the car is just too low to make that geometry work out.

RE: Electric Car Conversion

When looking at the complete shaft, the input yoke is the front yoke. So, the input yoke of the front joint is the one attached to the transmission. The input yoke of the rear joint is the one attached to the drive shaft. So, yes when the input yokes are turned 90*, the yokes on the drive shaft are inline with each other.

Here, watch this video.

https://www.youtube.com/watch?v=gmV4qwLfOMY

RE: Electric Car Conversion

I think the Spitfire had side-draft carbs, so there may not be a useful indication of what the crank angle once was, even if you still have the engine.

Engines with downdraft carbs typically had a 'wedge' shape in the intake manifold, so that the carb bottoms were parallel to the ground at design height. Take a close look at the manifold on any random old sedan you can find.

The 'crank nose up' attitude also pushes the front u-joint down, to minimize the tunnel height, while maintaining a reasonable distance between the flywheel ring gear and the ground. It also provides clearance under the front of the crank for the usual front crossmember and steering links. There was also the earliest Pontiac Tempest that used no u-joints, but the driveshaft was thin and heat treated to a spring temper, so it actually ran while continuously bent in the squashed-U shape.

Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

(OP)
OK, that video is worth at least 10,000 words...!

Guess I need to take my straps out and bolt the two 2-bolt flanges together and see what happens!

RE: Electric Car Conversion

LionelHutz, thank you for your persistence.

I don't know where I got the idea that crossed yokes were useful or advisable, but it appears that I was completely wrong about that.

To summarize, the illustration is correct as shown, and I have had some brain fade.



Mike Halloran
Pembroke Pines, FL, USA

RE: Electric Car Conversion

Just thinking out loud and (sorry) totally off-topic...

Even if one UJ completely "undoes" the effect of the other (constant speed in -> constant speed out), surely the connecting shaft will still have the torsional speed variation. So the system as a whole will have a variable rotational inertia, which will manifest itself as a source of (2nd order) torsional excitation.

Steve

RE: Electric Car Conversion

(OP)
A LPS to LionelHutz for the video, which was brilliant, and another to Mike for his gracious admission of error! That is very big of you Mike, and believe me I appreciate your attempts to help.

I'll try to video both arrangements on the car on stands to see if there's a perceptible difference, but the video has me convinced that my best bet is to bolt the two 2 bolt flanges together without the straps.

SomptingGuy, I do think you might have a point there- it seems there is still something going on which could excite vibrations, even when they are minimized by correct geometry.

RE: Electric Car Conversion

(OP)
Good thing I didn't wait- I received the Spitbits replacement straps today and they are MILD STEEL and only 0.030" thick like the originals- you can bend them over the edge of the desk! The originals were definitely spring steel...This is a surprise, because Spitbits is a pretty knowledgeable and helpful vendor.

RE: Electric Car Conversion

(OP)
Bolted the 2-bolt flanges together so the yokes on the driveshaft are in line. Though I noticed nothing different in video of the two arrangements running with the car up on stands, I did notice an improvement in sound and vibration at highway speed with the new configuration.

Thanks all for your help!

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