
CeramicSpeed’s Driven Concept Might Become the Most Efficient Bicycle Drivetrain - untangle
https://www.bicycling.com/bikes-gear/a22092182/ceramicspeeds-driven-concept-might-become-the-worlds-most-efficient-drivetrain/
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woodruffw
As mentioned (and slightly buried) by the article, the really fascinating part
is that we _already_ have consumer bicycle gears that deliver 97% efficiency:
a Dura Ace groupset is expensive compared to the stuff you'll get at Wall-
Mart, but they're sold at pretty much every cycling store. I wouldn't be
surprised if the Ultegra and 105 (Shimano's next two groupsets by price) were
nearly as efficient as well.

2% is nothing to sniff at in cycling (people pay thousands of dollars for that
kind of advantage), but there are other factors as well: resistance to stress
(sprints), ease of maintenance and service, and weight all factor into the
utter dominance of the current groupset design. It'll be interesting to see if
CeramicSpeed can advance their design on those fronts.

~~~
mrob
>2% is nothing to sniff at in cycling (people pay thousands of dollars for
that kind of advantage)

2% is nothing to sniff at only if you're hampered by the arbitrary UCI rules.
By far the biggest factor in cycling performance is air resistance, and the
obvious solution (fairings) is banned. The UCI has been disastrous for bicycle
technology. Most high-end buyers like to pretend they could compete
professionally one day, so they abide by the same rules, which means there's
no incentive to develop truly fast bikes.

The UCI rules should allow any safe design, and avoid giving an advantage to
richer teams by setting a price limit (bicycles are already required to be
commercially available).

~~~
jdietrich
Fairings aren't as useful as you might think in most circumstances. On an
upright bike, they need to be enormous to offer an appreciable benefit, which
makes them heavy and difficult to control in crosswinds.

The optimum solution is a recumbent bike - by going feet-first, you can reduce
your frontal area by more than 50%. With a much smaller frontal area and a
much lower center of gravity, a tail fairing becomes a practical proposition.

Fully enclosed recumbents can achieve phenomenal results in the right
conditions (Sam Whittingham's 91km hour record, Andy Wilkinson's 41 hour
LEJoG), but they immediately become a handicap with any sort of gradient
because of the ~20kg weight penalty and they're unbearably hot.

~~~
dmm
> The optimum solution is a recumbent bike

Recumbents are cool and much faster in some situations but pro cycling exists
mainly to sell stuff and upright bikes look cooler.

~~~
jdietrich
Recumbents have been banned by the UCI since 1934, so that ship has sailed. If
we had seen recumbents on the Tour de France for the last eighty years, they'd
probably look cool and upright bicycles would look weirdly old-fashioned.

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joshontheweb
I use a single speed bike at the moment. Not because I hate gears but because
I’ve never had a geared bike that didn’t constantly click on the outside
gears. It drove me crazy trying to tune them perfectly and never succeeding.
Forget increased efficiency. If a new design emerges that accommodates gears
and is simple to tune properly, then sign me up. No idea if the design being
discussed could offer this.

~~~
nordsieck
Have you tried out a bicycle with an internal hub gear? I don't know how loud
they are, but you shouldn't have any chain binding issues (and you could
probably run a belt if you wanted).

~~~
robin_reala
I use a Gates belt drive with a Shimano hub gear and it’s nearly silent
compared to a chain.

~~~
rconti
Oh man, I had a Ghost bike with a Continental drive belt that was a constant
pain in my ass until the belt snapped at 1500 miles and practically chucked me
in front of traffic.

REI really stepped up and Ghost warrantied the entire drive system as the
Continental system was NLA; they replaced the whole thing with a Gates Drive
system which is amazing.

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pgreenwood
If this drivetrain achieves its claims I will be very impressed. Shaft drive
designs have been around for as long as chain drives; and they have never been
as efficient. So mush is lost in the torsion of the shaft. A 2% increase in
efficiency is an absolutely massive gain. The cycling industry is littered
with flashy looking innovations that don't live up to the hype. The basic
design of a diamond frame and chain drive has not been improved upon for over
100 years.

But every now and then there are innovations that acually take hold. For
example, the slant parallelogram derailleur, hydraulic disk brakes, suspension
(for mountain bikes), and recently narrow-wide front chain rings. We shall see
how well this drivetrain goes.

~~~
jacquesm
Shaft torsion does not lose you much energy, it mostly acts as a torsion
spring: whatever you put in you will get back. The shaft will only warm up a
tiny little bit from the amount of energy that it will lose during a single
cycle.

Suspension _does_ lose you a lot of energy, which is why you'll never see it
on road bikes.

~~~
usrusr
Springs are terrible when driven by biological "pistons". Applying a certain
amount of force is much harder in some phases of the pedal stroke cycle than
in others and springs would make it impossible to go easy when you want/need
to.

~~~
jacquesm
It is a _very_ hard spring, not something squishy like front fork suspension.

The biggest downside would be eventual wear of the driveshaft, the losses will
be very low.

Note that almost every part of your bike acts as a spring in that sense, the
frame flexes a bit when you pedal, as do the cranks and the shaft. Even the
spokes in the rear wheel act as springs transmitting the force from the hub to
the rim (which is one reason why they are oriented the way they are, that way
they pull the rim along rather than that the spoke gets bent, the spoke is
stronger in that direction).

~~~
usrusr
Everything acts as a spring, and performance bicycle engineering goes to great
lengths to make them as as hard as possible. Frame flex under pedaling load is
measured, optimized against and a driver of buying decisions. Replacing the
chain with something more springy? Good luck in that market.

~~~
jacquesm
> Everything acts as a spring, and performance bicycle engineering goes to
> great lengths to make them as as hard as possible.

Indeed. So if you use a shaft to drive the rear wheel that would definitely be
part of the equation, I note they are using a hollow carbon fibre tube, which
in that particular dimension is likely not ideal for the application unless it
is given some more cross section. Even so, it is an interesting development.

> Replacing the chain with something more springy?

Chains stretch quite a bit, you'd be surprised.

~~~
mrob
"Chain stretch" is usually slang for chain wear. The chain gets longer as the
rolling elements wear down so people call it "stretch" even though the metal
isn't stretching. The actual stretch under load is very small.

~~~
jacquesm
I'm aware of the difference, but thank you anyway.

You can see the effect for yourself if you lock your rear hub and proceed to
push down on the pedal (you can see it because the pedal is a nice long
indicator effectively multiplying the distance the chain stretches).

A bit nicer setup is a micrometer at the end of a fixed section of chain with
a weight attached.

Chain _does_ stretch. About 1.5 mm under full load.

That's why you want chains with solid pins and solid plates.

What you are talking about is chain elongation as a result of wear,
essentially the accumulation of slop in the bushings the pins go through.

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scns
Check these out: [https://pinion.eu/en](https://pinion.eu/en) a german startup
which created a gearbox for bikes which works like the one in a car. Early
Investment came from an engineer at Porsche.

Disclaimer: not affiliated

~~~
bytesmith
Unfortunately, Pinion systems haven't really gained any significant market
share due to a) really high cost b) inability to downshift under load, c) a
1.5lb weight penalty and d) the frame must be built specifically for the
Pinion system[1]. Still, always great to see new approaches like this as bike
maintenance is a huge barrier to adoption.

[1] [https://www.singletracks.com/blog/mtb-gear/the-pinion-
gearbo...](https://www.singletracks.com/blog/mtb-gear/the-pinion-gearbox-
solves-common-problems-but-creates-new-ones-a-test-ride-review/)

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jacquesm
Very nice concept, I really like the fact that the casette is gone because it
occupies a lot of space leading to substantial weakening of the rear wheel
(the width of the hub where the spokes attach is a very larger factor in rear
wheel strength).

That gear does look like something that would do well in a meatgrinder, and
given the fall-out over just having disc brakes on racing bikes I don't think
that would pass inspection for road bike racing.

10 points for out of the box thinking though, a cardan driven racing bike is
very clever.

~~~
TheSpiceIsLife
I _cardan shaft_ just another name for a _drive shaft_?

[https://en.wikipedia.org/wiki/Drive_shaft](https://en.wikipedia.org/wiki/Drive_shaft)

~~~
jacquesm
Sorry, probably a dutchism...

We use the same term for the rear end of a car and for the drive train on BMW
motorcycles.

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AtlasBarfed
Yeah, that's going to skip under load and won't stay aligned.

Might be usable as an electric assist drivetrain and it was sealed up.

~~~
mirimir
Yes. Based on that photo, I can't imaging that the set of ring gears could be
rigid enough. Unless it was inside a strong casing. As in standard
differentials.

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NietTim
This is cool and really fascinating, technically, but ultimately a solution to
a question nobody asked and I don't see many benefits outside of a claimed
efficiency benefit while there are quite a bit of drawbacks. Also I'm failing
to see how this is different from shaft driven bikes [0] we already have had
for 'some time' now

[0] [https://en.wikipedia.org/wiki/Shaft-
driven_bicycle](https://en.wikipedia.org/wiki/Shaft-driven_bicycle)

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userbinator
_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?_

This reminds me of some newer automatic transmissions that use dog clutches,
like a manual one, relying on sensors and electronics to do the
synchronisation --- there is a very noticeable (and unpleasant) jerk in the
shifts, since it has to match the speeds precisely, and automatically reduces
throttle to do so.

Of course, with a human providing the power directly, that's not really
possible. I suppose you could add a "shift light", but IMHO that's just
overcomplicating things...

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robert_foss
Other options include CVT which offer continuous non-integer gear ratio steps,
but a lower efficiency of about 79%.

[http://www.enviolo.com/nuvincicycling/nfinity](http://www.enviolo.com/nuvincicycling/nfinity)

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nottorp
They mention something about an electronically assisted shifter. Doesn't that
defeat the whole point of a (non electric) bicycle?

~~~
jdietrich
Not really. All three of the major manufacturers offer electronically-
controlled derailleur gear systems. It offers minor aerodynamic benefits and
more reliable shifting performance with no real weight penalty. The battery
adds about 60 grams and the derailleurs are slightly heavier, but the shift
levers and cables are significantly lighter. That battery lasts for about 1000
miles of typical riding, which is more than enough for the target market of
racing cyclists.

The inconvenience and cost of electronic shifting isn't a good fit for leisure
and utility cycling, but it makes sense in racing where every marginal gain in
performance is valuable.

~~~
nottorp
Ah well, when I think cycling I don't think racing, I think out-of-town rides
where it helps if you're able to fix your bike using just some wrenches...

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nkristoffersen
My grandfather told me about a bicycle he designed that uses a CVT. Curious if
that’s a better direction for the future of bicycles.

~~~
jacquesm
You can buy these today, and many e-bikes use them. About 15% power loss means
that for an un-assisted bike they are not an option.

(Dutch link: [https://www.fietsenwinkel.nl/expert-e-
bikes/nuvinci](https://www.fietsenwinkel.nl/expert-e-bikes/nuvinci) with nice
cut-out picture of how it works)

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tomglynch
Unproven, can't yet change gears, based on an old design used over 100 years
ago that was given up on.

~~~
kwhitefoot
> based on an old design used over 100 years

Sounds interesting, can you point to some documentation?

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bigato
> A stock Dura Ace drivetrain returned about 97-percent efficiency.

Does anybody know the numbers of efficiency in fixie and single speed
bicycles? I reckon they should be better given the absence of a derailler? I
tried to search for it, but couldn't find numbers.

~~~
21
Another article on this technology stated that the efficiency gain comes from
there being only 4 points under load versus 8 points in a chain with
derailleur system.

A fixie also has only 4 points, since the derailleur is gone, so it's
presumably more efficient.

But the big problem is that there is also an efficient human cadence (I think
around 100 RPM), and a fixie has a massive problem here. So overall, a fixie
is massively more inefficient. Which I guess is no surprise, cycling
competitions are run with geared bikes, not with fixies.

~~~
bennyelv
This doesn't sound correct to me - the derailleur is on the "slack" side of
the chain so is never under significant load.

The only load is that required to pull the chain back from the crankset under
enough tension to stop it from drooping, which is provided by the spring in
the derailleur cage.

All the load in the chain system is between the cassette and the chainrings on
the top.

Perhaps a link to the article will reveal more? There's a lot of BS in bike
technology, so I'm automatically sceptical!

~~~
21
Maybe load was not the appropriate word to use.

Smith explains that that friction in a chain-based drivetrain is created
largely at the eights points of articulation, where the chain bends around the
chain ring, cassette and pulleys.

"Any time a chain articulates, friction is created. And any time it
disengages, friction is created," Smith said. "When you think about pedaling
95rpm, you are looking at 40,000 stiction points a minute."

In the DrivEn system, those eight points are replaced by four points, each of
which rotate on ceramic bearings. The chain ring's teeth and cassette's cog
engage with the bearings on the shaft, which itself spins on bearings.

[https://www.bikeradar.com/road/news/article/ceramicspeed-
dri...](https://www.bikeradar.com/road/news/article/ceramicspeed-driven-drive-
shaft-52587/)

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kentiko
I don't think the big cog will be stiff enough to not bend under the pressure.

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Baeocystin
"while the 13-speed rear cog looks like the unholy union of a compact disc and
the Sarlacc pit from Return of the Jedi"

After looking at the thing, it is a remarkably apt analogy, too. I wonder how
long it takes to machine.

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bentoner
Does anyone know if this would this be UCI legal?

~~~
jacquesm
Not a chance. That gear will rip your leg to shreds in an accident.

~~~
jdietrich
I have a large scar on my calf from a conventional chainring. If your chain is
on the inner ring, your crankset is basically a blunt circular saw.

~~~
jacquesm
Ouch. I very narrowly escaped that (but did break my leg :( ). On intermediary
'sports' bikes and mountain there typically is a guard ring mounted on the
outer gear ring to mitigate some of that risk. Most road bikes don't have them
though.

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hinkley
Would this design not be... less of a chipper shredder if they switched the
cylinders and the teeth?

~~~
King-Aaron
Yeah, I could imagine that getting the end of your jeans or a shoelace caught
in that, you're in for a bad time.

~~~
hinkley
I suppose you could do a number on your hems, but I’m more worried about feet
and calves. I’m thinking about a crash situation specifically. That thing is
more of a meat grinder than cogs. Granted, the front chainring is more of a
meat cleaver on a traditional bike. I knew a guy who got a nice free tattoo on
his right calf. Still gives me the heebies...

