Cool New Bike Drive Train

I had seen that one somewhere last week, very interesting!

I wonder if it works well enough and is reliable enough to be used by professional cyclists (with the Tour de France now going on).

Interesting.

Looks like they haven't got the gear change sorted yet, he talks about it will do this and will have that but never demonstrates it. So I'm thinking its a neat solution but still in development.

I'm also not sure if this will be so robust. But that's just my thought without any proof, it would be nice if they had a working prototype they could lend to pro cyclists to see what they say.

I keep looking for what might be a problem, but I don't see anything other than the bearings will be heavily loaded from the side, so I suspect the bearings will be critical, and possibly expensive... the concept is ingenious though...

What happens when you coast? Wouldn't one of the 'pinions' or the wheel gear have to have a sprag clutch/bearing?

Just add a freewheel hub.

Yes, the OP video shows us a sprag clutch (or sim) in the hub, we can hear it click.

'...have to have..?'.

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No. Most would prefer the ability to freewheel, but it isn't a necessity. Some actually prefer to ride 'fixies'.

These guys seem to be enjoying thoroughly the special abilities of their fixies.

This just proves that you can't fixie stupid.

“Fixies”? Never heard the reference before.

Let me see, YOU take a LOT of chances whilst I motor along with my grandchildren, whilst my concrete truck drives along his assigned delivery route, 45 Km/H blind corners that may well be littered with gravel...

No wonder so many men die of heart attacks aged 42 years, after learning just what the hell their kids are doing!

[edit] Yeah, what Lyn said!

It looks like it should be more efficient than a chain drive. Wear on the wheel gear should be minimal because there is no sliding between the pinion and wheel gear, as shown in the picture below.

Here is a close up of the wheel gear and the driving pinion:

https://www.designboom.com/technology/ceramicspeed-chainless-bike-07-10-2018/

The weak spot, I suspect, is the wheel gear, with the possibility of a tooth breaking, especially if the gear speed is not fully engaged.

It will be interesting to see how it stands up to use.

Yeah I think breaking one of those teeth would be enough to trash the entire rather expensive looking sprocket....

What about a belt drive with an internal sprocket setup....

I like it.

OK, but how do you "change gears"?

Velodrome bicycle?

I think they use a hub with internal gears....

https://en.wikipedia.org/wiki/Hub_gear

Internally geared hubs have been around since the turn of the century - the 20th century. Google Sturmey Archer. I have 2 bikes amongst my 17 with internally geared hubs. One shifts by backpedaling (just 2 gears) - the other by a shift lever on the handlebar.

Let's try another tack on this discussion. Why not combine the Sturmey Archer internally geared rear hub with a 4 or 6 speed derailor (how do you spell that anyway?). When I had one of the Sturmey Archers I could I could shift faster, with a very brief pause in power on the up-shift. The derailor could then add to the range of gears available.

Derailleurs are the norm, but they are a pain in the posterior. At least off road where I ride they are. I've bent 5 of them in 15 years with sticks lying on the forest floor. Amazing how they can just jump up into the drive train. Then you "limp" out of the woods to your car/house stuck in whatever gear you can get the thing into, or if bent bad enough, out comes the chain tool and you go single speed. I just put in a $200 one for a 1x12 drive train with a 50 tooth upper cog on the cassette and the second time I rode it, I caught a stick in it. Got stopped quick enough to not kill this one, but I know the warranty doesn't cover that damage.

Yes I put up with their limitations, but if we can eliminate them, which this new system does, we will be one more step closer to flawless mountain biking.

"... Wear on the wheel gear should be minimal because there is no sliding between the pinion and wheel gear, as shown in the picture below. ..."

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Maybe at first glance. Look again. There will be significant sliding/wear/friction between the driven gear and the bearing-cogged drive gear.

Consider the paths as the gears rotate. There is significant nonaligned relative motion that is not covered by the degree of freedom provided by the bearing cogs. Specifically wrt the 2d motion of the driven gear over the arc it is driven, the drive gear motion is a secant, i.e a straight line... zero curvature.

Theentire mismatch is axial to the bearing. The mismatch, and so wear and friction will be greatest for the smallest driven gear...the most highly loaded gear for which efficiency is most critical.

Note that this is a type of motion mismatch/wear/friction not found in usual chain drives.

...still 99% efficiency...?

What sets the subject gear train apart from these is, first, the cog scheme of gear ratio selection, and second, your images (it appears, anyway) use the axle sleeve as the structural member.

The first distinction is distinct in fact. The second is a matter of selection, and perhaps a rethink of the new design is in order if one objective is mass reduction.

Lyn touched on this a while ago - is this an elitist thing, or does CeramicSpeed see this being (eventually) on a common $125 dollar commodity bike? The proverbial better mousetrap, if you will.

Well I wouldn't think you would want the bearings exposed for obvious reasons, so I would envision an enclosed drive assembly, after all getting dirt and water into the drive mechanism would defeat the purpose entirely...so I assume this is just an engineers model type of thing....It's possible that the fancy sprocket could be produced via 3D metal printing tech and turn out not to be so expensive....of course it would take a while for the price to settle down....I don't see anything else that would seem to be exorbitantly expensive...

This looks more complex at $300 ....

It seems that leaning on the 'rolling friction vs sliding friction' idea so hard may have forgone some benfit to be fully committed to the core mantra...

Articulating cog teeth is an interesting idea. I bet cylindrical is not the optimum cog profile though. I also bet that there are cog bearing rotational axis alignments that offer less friction and wear than parallel to the drive sleeve...especially with cam controlled orientation or perhaps spring return.

Additionally, the articulating cog teeth might not be a great place for roller bearings. With such limited space, high load, and minimal speed and minimal total travel, plain bearings could be a much better choice.....the downside being you can't so easily sell the ''rolling vs sliding" pitch.

According to this, the most efficient transmission is the old fashion chain drive.

"Mechanical efficiency[edit]

From a mechanical viewpoint, up to 99% of the energy delivered by the rider into the pedals is transmitted to the wheels (clean, lubricated new chain at 400W), although the use of gearing mechanisms reduces this by 1-7% (clean, well-lubricated derailleurs), 4-12% (chain with 3-speed hubs), or 10-20% (shaft drive with 3-speed hubs). The higher efficiencies in each range are achieved at higher power levels and in direct drive (hub gears) or with large driven cogs (derailleurs). ^{[2] [3]"}

https://en.wikipedia.org/wiki/Bicycle_performance

If that's true, there's not much to be gained from the mechanical transmission. More can be gained by increasing the power the rider can deliver (recumbent bike), reducing the loss from wind drag (fairing), or reducing road friction (hard, high-pressure tires). At higher speeds, the biggest loss is due to wind resistance.

Diagram of partial power components vs speed using typical values Air drag power is initially very low and increases with the cube of the speed. Rolling resistance power is higher at first but rises only gently. Climbing a 5% grade is seen to be almost the same as continual acceleration with 0.5 m/s².

https://en.wikipedia.org/wiki/Bicycle_performance

I like your answer. There is one part that doesn't sit well though...

"...increasing the power the rider can deliver (recumbent bike),..."

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Recumbent bikes can have an advantage in wind resistance via reduced frontal area and perhaps a shape more conducive to lower Cd, but I don"t think of recumbents as optimizing the power a rider can produce or sustain. If you see it differently, would you walk through your reasoning?

Generally I agree....but are we talking about peak power or average energy expended over time?

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3924611/

And where do toe clip pedals enter into the equation?

In the vicinity of the foot/pedal junction.

I withdraw the question.

...remember, you are clipped in.

You may very well be right.

I've never ridden a recumbent bike, but my thought was that you could apply more force to the pedal with your back braced against a seat. On a regular bike, you also have to pull upward on the handlebars to exert more force on the pedal than your weight, requiring more energy than having a hard support to work against.

Having said that, a brief search has not uncovered any support for my theory. I suspect there are many more factors involved.

I've thought about it some more and reached the conclusion that an incumbent rider is basically using just leg muscles, whereas an upright rider involves more muscles. Since the rider is converting chemical energy in the body to mechanical energy (force x displacement of the pedals) and each muscle has a maximum power output (energy/time), the upright rider should have an advantage in total power output. (I agree with you.)

From what I've read, in practice the upright rider does excel at hill climbing whereas the incumbent rider excels in speed where aerodynamic drag becomes important.

Your rationale seems sound.

I would add that the leverage available to a recumbent biker may indeed allow greater pedal force to be applied in certain circumstances, but maximum power in cycling IIRC is typically achieved when spinning at a fairly good pace, typically around 90 rpm or perhaps faster. 90 rpm probably doesn't allow much benefit from leveraging off a seat back.

Also worth note is that upright frames meant for racing of all types for which the power delivered by the rider is among the most important factors (so not including things like downhill racing), seat tubes tend to be more upright, (i.e. less reclined).

You are entirely correct. For two gears to "roll together" without sliding, AFAIK, the axes either need to be parallel, or they need to intersect and the surfaces of the teeth need to be aligned so that the lines of contact also intersect at this point (aka. bevel gears).

"A bevel gear is shaped like a right circular cone with most of its tip cut off. When two bevel gears mesh, their imaginary vertices must occupy the same point. Their shaft axes also intersect at this point, forming an arbitrary non-straight angle between the shafts. The angle between the shafts can be anything except zero or 180 degrees. Bevel gears with equal numbers of teeth and shaft axes at 90 degrees are called miter gears."

https://en.wikipedia.org/wiki/Gear

The gears on the bicycle are apparently not designed as bevel gears, and while they could be, the geometry of the pinion gear (with the bearings) would have to vary as different gear ratios are selected.

The contact surfaces in involute power transmission gears do actually slide, which is why they need lubrication to work properly. The power transmission components in the bike drive are based on sprocket geometry and use a ball bearing on one side of the sprocket interface. An actual dynamic motion profile will show the rotation rate to be a little lumpy on the output side for a constant rotation speed on the input side. A large tooth count on both sides smooth's out the lumps, but doesn't totally remove them.

Looks like it'd make a nice cheese or flesh grater without a cover.

No information on price, as an add-on or OEM, but I see this only interesting people who spend $3-5,000 on a racing bicycle.

My $99.00 USD Walmart cruiser will stick with a chain drive.......... It shows no wear after 1,500 miles.

Yeah it seems like there would be a danger of the tips breaking off the sprocket....all the drive force applied to the tip of one tooth, seems the most likely weak spot to me....

Agree entirely.

I was wondering if, IRL use of the mechanism would be the sprocket being integral with the wheel, a composite 5 spoke affair with mounting bosses for the sprocket.

Very good idea, one of those ‘Why didn’t somebody think of this before?’ things.

I wounder if you could make an aggressive worm gear drive to a progressive wheel

...sort of like this , but more aggressive, and with the linear teeth extending to the center....the drive shaft would be shifted closer to the center to increase ratio...or maybe more like this....

I don't think I've ever seen a fully faced gear plate....

I don’t quite get your comment - like a CVT or an IVT?

I sent a note to these guys, someone from CeramicSpeed might stop in and visit with us.

Well it would have to be graduated in some way, perhaps 5 different gear wheels inside one another...then the shift would be from one position to the next...

Ah, no pedal while shift gears.

Offhand, seems more robust than necessary for a tour bike - maybe for use on the off-road trail variety?

Well picture a smaller drive gear with say 20 different speeds....the gear change would be quick...just a thought anyway...

But, but, I see the same number of teeth on both drive and driven gears.

Oh, that won't do at all....OK subtract one....

No, there's no way to vary the ratio.

"...all in all, we haven't done measurements but we feel this will be 15% to 20% lighter than..."

"... again, as I mention earlier, we did hit that 99% efficiency number..."

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Let me get this straight...they can handle the measurements and calculation to nail down efficiency, but aren't quite to the level of proficiency required to operate a scale???

Well, it is pretty at least.

Haha, I picked up on those comments too but the way you expressed it hit the nail on the head.

..."As it turns out, well-maintained bicycles lose an insignificant amount of energy in the gears and drive chains that transmit work from the pedals to the rear wheel: a new and lubricated chain can have an efficiency of upwards of 98.5 percent. [1] Most of the rolling friction therefore stems from the friction between the tire and the ground, which experiment shows to be proportional to the weight of the bike and rider. The ratio of rolling friction to weight is known as the rolling coefficient. On concrete or asphalt roads, the type of tire and pressure used on a bicycle can cause the rolling coefficient to vary from .017-.0021 yielding rolling resistances of 14.2 to 1.8 N for a bicycle and rider weighing a combined 85 kg. [2]

The dominant dissipative effect on the kinetic energy of a quickly-traveling bicycle on level ground is wind resistance. [1] The actual friction between the bike and rider and the air is small; the majority of the dissipated energy is lost as the travelling bicycle pushes air out of the way, creating a turbulent wake [1]. As this resistive force is proportional to the square of the velocity of the bicycle, it is described by the dimensionless drag coefficient of the bicycle and rider C = 2 F/(&rho v² A), where F is the frictional force, ρ the density of air, v the velocity, and A the cross-sectional area. It is measured experimentally that for a 70 kg rider 175 cm in height, a "traditional" bike with the cyclist in a sitting posture has C = 1.1 and A = 0.51 m², while for top racing bikes with riders in a "dropped" posture C = 0.65 and A = 0.40 m². [2]

Taking the worst case scenario for both the rolling friction and wind resistance for a 70 kg rider with 15 kg bicycle travelling at 10 m/s, we calculate (using ρ = 1.2 kg/m³)

The air resistance term would begin to dominate completely if we took higher velocities, but this seems like a reasonable estimate for a casual commuter cyclist.

Combining this with the results from the first section, we see that a bicyclist weighing 70 kg with a 15 kg bike traveling at 10 m/s uses up (in the worst case) approximately

If we had instead used the best case numbers from above, we would have calculated a power usage of approximately 696 W = 0.17 kcal/s, a factor of 3 improvement in efficiency."....

http://large.stanford.edu/courses/2010/ph240/stetler1/

Now we're getting someplace....it's the air turbulence creating that drag that's holding you back.....it seems...

http://www.bikecommuters.com/2010/04/04/just-ask-jack-fighting-the-wind/

But what is that in miles per sausage and egg mcmuffin?

450 calories = divided by 50 calories per mile = 9 miles per Mcmuffin....or roughly a mile per bite....