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Alloy flywheel

Alloy flywheel

Alloy flywheel

I want to make a lighter flywheel for my car now that I have the engine and all its other parts completed.
Firstly, Ill talk about the material and method of manufacture.
Im planning on turning it from billet aluminium, 6061 T6, or perhaps, 2024 T3, I haven't decided yet.

The oem fly is approx 280mm in diameter o/a, and approx 24mm thick. This is turned/ramped down in the centre on the clutch face, inside the ground clutch 'circle' to approx 10mm thick to where its bolted to the crank With 6) m10x1.00 metric fine bolts. It weights a ton also, which is why I want rid, more on that later.
The ring gear mounts to its outer edge, closest to block and is approx 11mm wide.

For the clutch surface on the flywheel Im going to use one of Sweden's finest saw blades, the material properties seem to check out and its 4.5mm plate, Im going to spin it on the lathe and grind out the disc size I need, should work pretty great I reckon?

For fixing Im thinking of using maybe 16-20 screws, something of the 10.9 grade and in an m6, I looked at perhaps torq set for the simple fact of ease of removal and a pretty strong head.(No doubt another part of the engine will give out long before I have to replace plate!!) I had thought of heli-coiling the threaded portion in the flywheel to accept these countersunk screws as I feel the heli-coil tap cuts a more rounded cross-section thread profile, than a standard metric tap, leading to a lesser chance of stress risers. But I think Im getting over worried about this. I will have 3 times the diameter of the screws there to tap so Im well inside the limits. But Id like to hear peoples views on this, and wheather Id be better off forgetting about tapping, and just let them through and fit a nut to them at the rear? I have the room.

The same apply's to the pressure plate fixings, there is 6) m8 bolts holding it on in total and they sit pretty near the outer edge, from memory approx 10mm from fly edge to hole centre. There is also 3 location dowels in total equally spaced between the bolts 120 degrees from each other and on the same m8 bolt hole pcd. Will tapping these through be ok without further treatment? Threaded depth will be the full 24mm.

For ring gear security Ill shrink it on there and fix it in maybe 3 points with some allen head m6 bolts, counter-bored into both the ring gear and the flywheel to provide clamping force should things get loose. These drilling's may also break through 1/4 way into the ring gear material to provide a 'key' between the fly and ring.  

The original flywheel is 10mm thick where it bolts to the nodular iron crank, Im going to bring this to 14mm on the alloy version, and ramp it out to the plate area in the nicest 'sweep' I can cut, and fit a 'flex ring' under bolt heads to prevent galling when torquing them up. This is the maxium thickness I can go here before I come out and touch clutch disc centre portion. The major stress that I see as being an issue is clutching it at max rpm, and the axial trust loading/unloading/deflection(if any) that may occur at that time.

As for all the other dimensions, they pretty much will be the same, can anyone see a problem with this?  The rpm is pretty small, it will NEVER see over 8k, Limiter is 6.5k. I cant see a drastic down-shift happening to bring it over 8 at that.

Will I have issues with heat? Im thinking the alloy will conduct the heat from the steel plate pretty good and Im sitting the disc in there dry, I feel any form of chemical bonding would insulate things further.
Im guessing perhaps that it may see high temperatures on a hard launch or perhaps the odd hill start. This could possibly return the material to its pre heat treat condition? Perhaps not, its a hard one to calculate, but I dont hang around with the clutch.

Im also thinking the disc can be a clearance fit in there(outer only, inner 'step' will be machined away and it will be level there, ramp to crank bolt area starts here)
Does this fit sound ok?

Now for the reason Im fitting a lighter flyweel, real reasons why I need to,
Because of my cam profile, things only start to happen at 3.5k, the power band is fairly short, but a good one. I cannot spin the wheels too easy pulling away so any extra time I can get getting to my 'on cam point' will help.

Im also in favour of removing mass of the rotating assembly, as for 1kg I take off there, Ill be loosing 1kg off my sprung weight also, so its two fold, with the gains in favour of pulling weight of the rotating parts of course when it comes to 2nd and 3rd gear.

Im not too worried about how it will idle after, out of 14 cars one Idled perfectly, it was a straight 6 'German sedan' with a 5 in its name, which, strangely I sold after two months because it bored me a bit as it was too reliable.

As for hills, and lifting your foot and all that, that doesnt bother me either, and I know the effects.

Given the fact that its all going into a right hand drive car, and the gearbox on the left, flywheel entry to cabin wont or 'shouldnt' kill me, nor will it sticking itself in the road, nor will it if it exits bonnet, which it wont, as a dual mass 'just' has the inertia to do so. Considering this will be 4 times(approx) Lighter than a dual mass that then leaves exit through the front grille a possibility, but of course, there will be no-one infront of me, right ;!

Im confident Ill will be fine, I just need one of you guys to read the above, and tell me what you make of my thinkings.

I possibly could buy one, but Id prefer to make, as I seem to have a lot more time on my hands than I once had due to the 'current climate'. I dont really see it as not working or being an issue, do you?

Thanks as always in advance guys, if you see any issues with the above please do shout before I head out and start making a massive pile of swarf!


Ps, if it makes any odds, I still have my torsional damper bolted to the crank nose, and the engine is still running within its factory limiter rev band.



RE: Alloy flywheel

"strangely I sold after two months because it bored me a bit as it was too reliable"

Yeah, that's pretty strange, all right.

Are you hoping for Less robust performance from your flywheel set up?

RE: Alloy flywheel

No Im not, but I fine reliable cars give me nothing to think about in the evenings.

RE: Alloy flywheel

Awwwww!  You need to start racing a vintage Mini Cooper and a vintage Lotus Cortina.  You certainly won't run out of things to think about OR replace and repair!


Rod sad

RE: Alloy flywheel

Rod, come on now, you know what I mean when I say boring cars...
Im not trying to make something unreliable, Im making a point that it will probably outlast other stuff....I drive hard, when something breaks like a drive shaft, It means that the part just before that is working very well> Engine.

Im going to go ahead with this in a day or two,


RE: Alloy flywheel

And all this time I've been thinking there was a difference between driving hard and driving abusively.  Silly me.  Silly endurance racing series.


RE: Alloy flywheel

So does anyone want to answer my questions or pick holes in my wording instead? Because if its the latter let me know and Ill get the post taken down, thanks.

RE: Alloy flywheel

Why not just buy a steel insert that fits your clutch disc friction area (and the bolts to hold it on) from Fidanza or whoever and build the rest of your own wheel from there?  You'll have the benefit of greater experience that the material and dimensions will be satisfactory.  Trust me – I know what it's like to have more time to do things myself than spare cash to purchase everything ready-made.

Re: reliability and boredom.  Complaining to an audience of engineers that the first has caused the second is just begging for comment.


RE: Alloy flywheel

Norm, thanks for that, I didnt actually think of that, why I dont know.
As for your remark on knowing what its like to have more free time than cash makes me feel a bit better also.

''Complaining to an audience of engineers that the first has caused the second is just begging for comment''

As for that comment, I thought some would get it, possibly the older guys. Maybe I worded it wrong I dont know. I probably should have said that a perfect reliable car cant be improved on, or bits added it to it, like is possible with my Vw Mk2 Gti.

Again, thanks Norm, Just picked up some 6082, which is our version(European) of 6061.
Boredom can Indeed be a bad thing, but being Idle is worse, Im almost finish casting/milling my own 16v cylinder head too...

Regards, Brian,  

RE: Alloy flywheel

It's just not to many people have access to a lathe with say, 20" swing over the bed? Or a dividing head of the same capacity. Different strokes, I guess, but unless you just really enjoy swarf curl up & fall on the floor, I personally don't see the attraction.

Goodness knows, if you can afford the machine tools required for this project, you can surely afford to buy the best flywheel out there. Not to mention being a skilled pattern maker & foundry man, in addition to a machinist.(and you better be jam-up to make a cylinder head).

Again, i don't mean to be judging you, people do strange things that I don't 'get'. eg the "billet Cobra"; (God, how I hate that word 'billet') Please, post some photos on this site, or photobucket, or somewhere.

With all this time on your hands, I bet you have a web page showing these projects? Please post it, if I am correct.


RE: Alloy flywheel

Ok, well here goes seeming that you asked!

''It's just not to many people have access to a lathe with say, 20" swing over the bed? Or a dividing head of the same capacity. Different strokes, I guess, but unless you just really enjoy swarf curl up & fall on the floor, I personally don't see the attraction.''

I have, and its mine, I got it many many years ago for a song. I built the dividing head for it myself. Its accurate.
Its not so much seeing the swarf curl up, but the journey needed to end up with the required part. I know what I need, but cannot afford to buy all the ''good bits'' or want anyone else's parts in my engine for that matter, as they sometimes are not exactly what I want.

''Goodness knows, if you can afford the machine tools required for this project, you can surely afford to buy the best flywheel out there. Not to mention being a skilled pattern maker & foundry man, in addition to a machinist.(and you better be jam-up to make a cylinder head).''

Thats the thing, I cant afford fancy machine tools,I have old basic heavy machines, perfect actually, for what I need, as for cncs, they're fine for production work and dont we all love to see them whizz. A lot of people forget that a manual machine is as accurate as the guy turning the handles, Im ok with that.
I was a cabinetmaker for a long time so working the green stuff is easy, as is making any conceivable pattern no matter how complex.
As for the foundry, I made my own smelter, a small one to start with, for doing low volume melts, The bigger one for the head is a tar barrel, lined with fire brick, and heated by 4 propane burn tubes all aimed tangentially at the interior. I can melt large volumes with that, plenty for the head even at half of full tilt. I also had to make the crucibles too. I live in rural Ireland you see, so anything fancier than a hammer and a hacksaw has to be ordered from overseas. That, and the cost of this stuff incl shipping is a no go.
Machining isn't a problem, I have a lot under my belt from a wide range of very different aspects, and I know how metal behaves when it comes to machining. A head is pretty simple that way to machine if you break it down into stages.

As for the billet car, I agree, that was a little pointless, and I didnt really see the wow factor at all, a ton of 6061 a pc and a cnc was all that was needed. The body work did require skill and craftsmanship though, I will say that.

As for the head, its been a long road, from the design, testing of design(port models)The best cc chamber shape, the moulds, best port attack angles, How to form the moulds, the waterway jacket core box for the co2 cure sand(that was a head scratcher for a while, lol) to the types of sand, the type of alloy, how chills can help, the pouring temperature, the riser locations, the srue locations, where the cold fronts were going to meet, having them meet outside the mould itself, shrink, core sand porosity, the best choke angle to set the built up mould at, speed of pouring, amount of alloy needed(this was harder than I first thought, I have not got autocad) I did it via water displacement and the patterns, in the end)
The 5yrs reading and testing I did on casting, not incl head design, metallurgy, flow, head designs that are not so good, the best combustion chambers, why they are, moulding sand, reverse engineering of around 300 engine parts, hardness scales, heat treatment, thermal conductivity,
You may or may not know that there is little casting info out there as it is a dieing trade, there is books on the subject, theyre only so good, Ive read them all, unless you are lucky enough to work in a casting house, then you have to do all the testing etc yourself, to actually prove to yourself all this writing, and find out what changes make a different in the real world> and why they do.
Then onto what things really matter, and what things dont matter so much, be it tolerances,(no point having high tolerance on a flange face for example..)or how cool your machines look or how worn they are, if your doing the entire thing yourself, you can become aware of all this, look out for it, compensate, etc.

Lets go back to where I am again for a minute, I live in rural Ireland, Jobs are not to be had in this line of stuff, anyone that knows me, knows how skilled I am and know that I find a problem no problem. I dont really think anything is unachievable no matter how complex, as H once said, If you think you can, or think you cant, your right. Im dont go by the latter!
This is something Ive wanted to do for a long time, since I was about 8 actually, engines always amazed me,  I read Hilliers Fundamentals 3rd edition when I was 9 and Fred Puhns HTMYCH 6 months later and its spiralled upwards since then.
But all this is no good for people that dont know me personally. My c.v consists of a blank sheet of paper, I was unable to fund my way into and through college also.
Thats pretty much what brought on all this, I made it my goal to study and carry out all operations myself, incl design, Ive been studying Mech engineering for maybe fifteen years now, there isnt a day that goes by where I dont learn something new. I dont move on from something until I understand things fully, and until Im happy that I do.
I also have not got complete autocad, its just too expensive, so, all of my drawings are done on a drawing board, and all calculations done by hand. It takes a while, but the gear does not cost much.
Im hoping in time, I will have enough experience build up from doing all this, and proving that I can do it 'all' completely will result in people taking me seriously then, which, they seem to be already as Ive already got 3 offers which makes me feel good.
My goals are simple, that is, to build a cylinder head that will outflow and oem head with 1500euros worth of porting work done on it.  
In time Ill build a gearbox also, and it will be fully sequential. Ideally, Id like to design and build an f3 car also, but I cant see that happening before Im 30.

As for pictures of the cylinder head workings, I cant share at the minute, I have no pictures watermarked, and Ive also promised that the pictures will be hosted on just one very popular Vw forum, Im not going to break that promise.
Please do not doubt that its all a big story, many of which you and I have read online, you will be proven wrong.

Im funding the materials I need by casting very simple parts such as coolant flanges and a couple of manifolds for the odd rally guy. I can cast 30 flanges per hr, and machine then in another hr. Time spent in jig making makes this possible.

So thats pretty much my story guys, Im not asking you to approve or disapprove of my work, its my passion, and my only way at the minute of possibly ever getting a job again given the way things are at the minute here. Im hoping in a few yrs that maybe Ill get hired doing something, I think wanting to learn and do all this myself shows how serious I am, over a guy that had to be taught it or wouldn't dream of doing something like this without getting paid. Or perhaps Im a fool, who knows.

Ive done a lot of reading on here and Id like to thank you all for that info, I envy you all in your current positions, and Ill admit, sometimes I have to ask some questions when I really am not sure. The European and Us specs and the fact some are the same alloy, but different numbers, and some are a different material make up confuse me the most.

Ill have a root around for a thread with some of my lastest work in it,they are on a few forums, and tend to be picture heavy.
I should have the head pics ready to host in around 3months, it all takes time doing everything yourself and is not simple.

Regards, Brian, From a very damp Ireland!
(Man that was a long rant lol)


RE: Alloy flywheel

Thank you for your reply. As an amateur machinist wanna-be (Emco-Maier Super 11,Bridgeport BR2J2) I am also interested in the "process". In my case, however, that "process" is a means to an end, not a "journey of discovery".

Just my cynical, practical side.

Still like to see some pictures, though!

Good luck on your projects!

RE: Alloy flywheel

Im intend having a great engine at the end of this, its just taking a long time to end LOL.

I hear ya on the pics, Ill notify you dont worry. Ill post a link later to other stuff once I figure out how to on here!


RE: Alloy flywheel

Back to the flywheel.
I'm not convinced that it needs an iron face at all.

I'd have thought so, in days of yore.  Then I bought a commercial aluminum flywheel (for my Corvair).
It was bare aluminum, all over, no facing.
I'm not sure, but I don't think it was anodized either.

It worked just fine for a very long time.


Mike Halloran
Pembroke Pines, FL, USA

RE: Alloy flywheel

Thats pretty amazing Mike! Ill have to have a think as to how it could have been done. Now that you mention it, galling would not occur pending clutch material, and the heat would indeed be drawn into the main body and away from contact face.
Id imagine a type 3 anodize would only better things further.


RE: Alloy flywheel

I had "Mother Mueller" (Lee Muller, rip) build me an Al flywheel for a Lotus twincam back in the late 60's.  It was done sans steel face for clutch, instead it had a 'sprayed on' surface of a much harder material. Worked fine for quite a few races using a fibre clutch.  Put a Tilton multi puck metallic on it and promptly killed it.  Re machined it to take a commercial iron insert and all was well again.  In the new form it raced for another 30 years...It's still viable today but, we no longer use that B&B system.  Now use a 5" Tilton multi plate clutch and superlite steel flywheel.

Sorry, long way round to say that I know the add on surfaces may work, I just don't see them as viable for common use.


RE: Alloy flywheel

You dont see which one usable for common use Rod? The sprayed, or disc insert? The insert lasted you 30yrs?



RE: Alloy flywheel

No.  I did not say that.  The insert lasted a couple years, maybe 20 races until I used a metallic clutch.  Don Oldenburg of Design Products Racing repaired it by installing an iron insert....THEN it has lasted a long time.  It just sits on the shelf now cause we don't quite want to get rid of it...kinda part of the Lotus Cortina's history.

Even when I was still using the original Mueller unit, the surface was prone to cracks/checks in the surface.  It did not fail as long as I stayed with a fibre faced clutch...However, as the power was increased, the fibre clutch could not do the job.

Our current Tilton multi plate uses fibre clutches...BUT it's a whole 'nuther deal entirely!!!


RE: Alloy flywheel

Ah I see, so 'then' with the iron insert it lasted a long time.
Indeed, multi's are very different, less per face an all that...


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