I have been watching it for past couple months. Great idea!
It will be interesting to see how it evolves. I think it will eventually make it's way internally in the frame.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

That would be pretty awesome as long as it doesn't make maintenance/access to the drive impossible for anyone other than exclusive workshops.

Andrew H.
www.mototribology.com

I used to work in the industry, it can be easily done. It's the market that drives it.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

Their pinions appear to comprise a ring of ordinary Conrad bearings, with no housings to support the outer races. Stressing a bearing race in that way usually shortens its life.

Mike Halloran
Pembroke Pines, FL, USA

Did you hear the comment about 8hrs to machine the rear sprockets? So the back cluster will only cost what, $1,000?

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

Oh yeah, it seems like there is loads more to do before this thing is ready. I don't think any of it is limiting feasibility yet though. I like that they don't appear to be rushing into it. I mean, I haven't found any indication that they've integrated a shifting mechanism yet, so there's a long road ahead still before this could enter the market.

I think its great they are trying something:

• out of the ordinary
• visually appealing
• efficiency/performance driven
• just plain cool technologically if they can make it all work

Andrew H.
www.mototribology.com

Why not dump the mechanical stuff altogether and use pedal-electric. You could have zero gears and no mechanical linkage and a whole lot more. Pedal a generator and feed the traction motor directly. It would even remove all the bike frame linkage geometry constraints from variable geometry bikes with suspension.

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

itsmoked, the average rider can only produce about 1/4 hp for any length of time. This means efficiency is vital, and a generator/motor combination can't match the efficiency of a chain drive.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. - http://xkcd.com/319/

itsmoked,

Unless you have an electric motor that is powerful and efficient throughout its speed range, you need gears.

--
JHG

I'm a cyclist. I do it for fun and exercise. For me personally, I would never ride a electric bike unless I went on vacation somewhere and rented one and all they had were electric bikes.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

ctopher, wouldn't it be a lot more exercise to use the generator to run an electric motor than it would by a direct mechanical linkage?

And wouldn't it be more fun to use a high tech solution as a means to a simple end for the pure joy of getting to explain it to people who don't understand it at every opportunity?

Andrew H.
www.mototribology.com

Quote (ACtrafficengr)

generator/motor combination can't match the efficiency of a chain drive.

Not sure that's true anymore. Motors and modern drives run in the upper 90% ranges. What's a bunch of chain and gears efficiency?

Quote (drawoh)

Unless you have an electric motor that is powerful and efficient throughout its speed range, you need gears.

Definitely not true anymore. I'm talking about a system that's like a diesel-electric locomotive. They store nothing and they start standing-still trains weighing 20,000 tons and bring them up to 90MPH while not shifting a single gear.

Now if you add a single scuddy little battery (18650) you could store braking energy and get it back when pulling away from that $%^@&* stop sign.

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

So, if your generator is similar, 90% system efficiency should be possible. Interesting.

I found this:

Quote (On the efficiency of bicycle chain drives, James B. Spicer and others, HUMAN POWER Vol 50, http://www.ihpva.org/HParchive/PDF/hp50-2000.pdf)

Experimental results indicated that the efficiency of the chain drive varied as a function of chain tension. It was found that the efficiency varied linearly with the reciprocal of the average chain tension with the highest efficiencies occurring at high chain tensions and lowest at low chain tensions. For example, the highest efficiency measured in the study, 98.6%, was measured at a chain tension of 305 N and the lowest, 80.9%, at 76.2 N.

I'd always heard the 98.6% efficiency result, and never heard the 80.9% figure. It's also interesting to hear that chainline tension has such a big effect. I would have thought chainring/sprocket offset, sprocket size and lubrication would have been bigger.

So your idea could be competitive. For someone that just wants a reliable bike without fiddly shifters and greasy chains, it might be tempting. If you used a variable speed drive so the rider could maintain a cadence of 80-100 rpm, how would that affect the efficiency?

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. - http://xkcd.com/319/

MotoLuber,
I prefer the old style crank/chain method. I get more exercise using my own muscles powering the bike. I average 40 miles per ride, average 20 mph.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

AC; That's an interesting bit about chain drive eff. I wouldn't have thought it was that high, though I've never really sensed much heat off of a chain drive like I do off of belt drives or especially out of gear boxes. I still wonder at a bike chain drive with its diddly-squat derailleur and couple of N of tension.

Pedal rate; That would be the advantage of a wee bit of storage, you could conceivably start from a stop and immediately be pedaling at 80 rpm while the bike accelerates up using an unrelated or rather loosely related, to pedaling rate, curve. Ultimately the bike comes to whatever steady state speed the pedaling force is providing. You could have a thumb rate control that 'suggests' the speed you're after and the result is more pedaling force at the same exact pedaling speed - pedal speed kept constant. Interesting in that you could thumb up a mountain climb that on level ground ultimately results in hauling ass, whereas that's pretty hard to do with the usual setup as more force would result, on level ground, in out-of-range pedaling rpm.

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

itsmoked,

Perhaps the diesel electric trains are efficient while running at some planned constant speed. Do they need to be efficient while they are accelerating?

I am familiar with permanent magnet DC motors. At constant voltage, the torque curve is a straight line from the stall torque to the no-load speed. The power curve is a parabola with zero power at stall and no-load speed, and maximum power at half no-load speed. The maximum efficiency occurs at two thirds no-load speed. Motors like this perform well on drag strips because their maximum torque is at stall. They are great for accelerating.

I have not worked with AC motors.

--
JHG

drawoh; I don't believe the efficiency is greatly different in accelerating trains verses steady state trains since the engines tend to run about the same speed and that's in their power-band as compared to, say, an automobile. Trains on average including stops and starts move a ton 480 miles on a single gallon of fuel though that's mostly about steel it's still includes dishing up thousands of horsepower.

I'm not clear on specifically the motor speed verses efficiency. I suspect it stays pretty high because a motor doesn't really realize it's being run away from its design speed because the magnetic saturation is kept constant. From a 'load' perspective they do well keeping up around high %80 eff down to 25% load while rising quickly back to the 90s by 50% loading.

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

The Ceramicspeed drive is a nice engineering adventure and a beautifully machined system of parts. But it does not have all the goods their Youtube videos indicate or intimate. Their representative is a smooth talker and has the script well memorized and he is proud of the product and the potential. The issues I see:
1. Shifting between gears is going to be difficult or impossible at high rotation speeds - hence, why none of their videos show gear shifting. They do explain a potential method of shifting using pre-machined shift channels and software/sensor control but as complication is added so is potential failure. The slightest bend/deformation of any of the driven cogs' teeth will send this system into total chaos/failure . . . (If there is a video showing actual at-speed shifting being done - I missed it and I will eat crow on this observation )
2. The claim of their system not being limited for gear ratios is misleading. True, additional cogged teeth could be added radially (out to the limit of the wheel radius) since the thickness of the cog cluster does not increase, but the driven cog wheel is a disk and as mass is added radially, the rotational inertia of the system increases. This will have to be a stiff, wear resistant material. Aluminium won't last and with grit and contact pressure, even steel or titanium, etc. will wear. Hmmm, mass applied at increasing radii - efficiency will be affected . . .
3. The final drive bearing "sprocket" will only stay engaged to the driven cog wheel if sufficient side load is applied to prevent the drive from skipping out of engagement. The stiffness of the driven cog wheel decreases as its radius increases. Thus, the drive will be very prone to skipping as the drive is moved to the larger radius locations (lower gear). Oh, and the drive bearing sprocket has rotating bearing drivers that geometrically do not want to stay engaged in their drive "pockets" because they are intrinsically trying to roll out/off the surface of the driven tooth. Only cross load/clamp pressure of the axle bearing set can hold these faces together. As clamp pressure increases so does the mechanical loss of the system. I suspect the gear position Ceramicspeed chose to use in their videos is the best working position on the whole prototype.

I'm a gearhead so I love beautiful machines and mechanisms, so my enthusiasm was raised when I saw the original post. But I got pulled back to earth after checking it out. I ride about 160 miles per week by bicycle, year-around, rain or shine and I will harp needlessly about the simplicity, ruggedness and efficiency of the chain derailleur system used on bicycles. Generally, the chain and sprocket system on bikes can be neglected completely and it will still get you where you want to go. An abused chain and sprocket system will make noise and efficiency will be reduced but can it transmit human power to forward motion of the bicycle? Yes. Reliably? Yes. Inexpensively? Yes.

I'll keep checking on the development of this drive to see where they can take it. I am a realist and I believe a wall of technical/material capability will doom the drive - some of the comments on the Youtube videos are expecting just throwing more money at the problems will solve them - the drive can be made from Unobtainium and it will be infinitely light, infinitely stiff/wear resistant and inexpensive. If only I could get a hold of some of that great material!

Shifting looks like the death of this fascinating idea. I agree with Brian Malone that shifting is the crucial point, but for a different reason. Although I agree with what he says about it.

This rig is a brilliant idea on paper. I admire the people who thought it up. It might work flawlessly in a clean lab and achieve everything they claim, including the shifting.

But get that bike on the road and get some dirt in the drive train, especially the rear cog. That will be the real test. I predict that it will fail completely. The dirt will prevent the mechanism from shifting reliably.

Even if it doesn't, the dirt will degrade the efficiency so much that the old chain drive with derailleur would be better. I also suspect that they would have trouble keeping the dirt out of the bearings.

The only way to avoid this disaster is to enclose the entire drive drain. If they can figure out how to do that at an acceptable cost and weight, then they might have something. But I predict that they won't be able to do that either.

I think it's a great start. You have to build it first to test the idea.
It may (or may not) turn into something cool in the future.
I'm not going to say it will fail. Nobody knows that. Some great inventions were destine to fail by others.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

Windward, agree completely with you on the issue of gunk and debris packing into the drive wheel cog disk/'cassette'. This drive will have to be shielded/enclosed to have even a slight chance for successful operation under real-world conditions. Adding an enclosure adds weight.

Ctopher - yes, building a test assembly is a start. I will be watching to see how the team solves the technical hurdle of making this system shift reliably under load and at speed. The challenge is daunting. Especially, if no clutching or synchronizers are implemented. The drive pinion will have to move only at the right time to allow its rotating drive bearing elements to leave engagement from a given location on one cog wheel to re-engage to a correct drive pocket on another cog wheel without mechanical collision. This is going to be a dance of matching the angular speeds of two systems that must momentarily become disconnected during a shift event. By definition, the cog wheels' pitch has to be at minimum the width of the pinion drive bearing face width plus some clearance gap on either side otherwise the positioning of drive pinion would have to be absolutely perfect to prevent partially engaging adjacent cog wheels. The cog wheels each are fixed number of "teeth" and the drive pinion has a fixed number of drive "bearings" so the shift points will almost certainly be only at predetermined shift channels/points. Making the transition from one cog wheel to the next in a near instantaneous manner during a shift will be tough. Unlike a chain and sprocket transmission where the chain transitions from one sprocket to next with power slightly shared between the sprockets during a shift, the Ceramicspeed assembly must make a complete jump from cog wheel to cog wheel. With power applied to the driveshaft, at the moment of disconnect from one cog wheel the resistive force on the drive pinion will go to zero, the drive shaft will spin up (the rider is still hammering on the pedals), only to slam into resistance when the driven pinion's next drive bearing has rotated around and hopefully is timed properly to meet with a drive pocket in the target cog wheel. I can feel the crazy leg spin that will happen as I type this! If the shift engagement does occur, this will be a slamming engagement at the pinion drive bearing and cog wheel faces. If the shift misses, the rider will have to stop pedaling to let the drive engage, then try to resume cadence and power application. Wow! Trying to shift through multiple cogs will be really ugly. I am a gearhead and I am rooting for their success - shifting this system is a major hurdle. Making the idea demo prototype has been the easier part. Often with a design the toughest 10% takes 90% of the effort!

Just found this website Link

gives some more views of the Ceramicspeed DrivEn design and prototypes and a little better view of some of the components. One of the 3D printed cog wheels shows some of the proposed shift channels - Ceramicspeed could fully optimize these to perform as the synchro for the drive pinion.

As quoted from the Cycling Tips story: “We talked a lot about this automated system and the brain,” said Alex Rosenberry, the engineering student who managed the project on the University of Colorado side of things (and who now works for CeramicSpeed as a contractor). “The system would have to be pretty intelligent to know how fast the system is moving. It’d have to be pretty smart to know how fast it’s moving, which tooth track to select to make the shift happen. Would you have to back off to shift under high load? We’re not sure yet, but there’s definitely potential to make it work.”

Crazy! Gears, bearings and drive shafts! All that remains is making it shift smoothly, reliably and able to sustain torque loads without jumping teeth.

Every time I look at that big rear plate, I think about all the times riding seeing all the stuff on the road. Imagine a piece of plastic bag flying up and getting trapped in there! It's looks too easy to get trapped, and a b*tch to remove!

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

Ctopher, I'm confused why this seems to be the hangup a lot of people have (not just your post, I've seen it elsewhere too when I was first looking at this)

I see no reason why there would not be a cover over this to protect it from debris. I just assumed that would be the case. Plenty of lightweight material to use for what I would think would be a simple protective cover.

Andrew H.
www.mototribology.com

It's the first thing I would do, design a cover for it.
If you go cycling a lot, you know debris 'will' eventually get hung up in the components.

Chris, CSWP
SolidWorks '17
ctophers home
SolidWorks Legion

Sand, dirt and twigs will be a problem unless they can enclose the gearing system.