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.
There isn't really much difference in efficiency with price in group sets until you get into the really bad cheap stuff. Most of the differences are cosmetic or ergonomic and status related. Chains and bearing and cogs are the only items that affect efficiency and they are all pretty good. Good chain line and proper maintenance and lubrication make more of a difference.
Internal hubs are slightly less efficient overall and this depends a lot on the internal design and which gears are in use. But even these are something like 94% - 97% efficient.
Shaft drives have been the "next thing" since the end of the 19th century but have never managed to combine reliability and efficiency well. I doubt an exposed mesh 90 degree gear set with what look like teeny tiny exposed ball bearings are going to be as efficient after a good splash of water laden with brake dust and road grit. It might work if they enclose the whole system.
This isn't true. Rolhoff hubs can approach that for some gears, but bikes with them start at $2K. Nothing else except derailleurs are even close:
Also, current shafts and bands reduce speed another few percent.
It should be noted that the guy who said it could have easily lost 500g by a minuscule adjustment to his daily snack intake...
This seems like an exceptionally silly expense for a device which is designed to carry two pounds of water around!
It's just funny how many wannabee Eddy Merckxs seem immune to that truth, and we who grok it like to snicker when we hear discussions like the one cited.
500 grams is ~10 calories per day for a year, and 10 calories is 1/25th of a Snickers bar or about one eight of a potato.
Either way, he'd get the same effect has the extra $3500 would have, which was what I found amusing and why I mentioned it.
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).
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.
Recumbents are cool and much faster in some situations but pro cycling exists mainly to sell stuff and upright bikes look cooler.
Since most bicycle racing is dominated by climbing hills, I don’t think anyone would ride a recumbent even if it was legal.
Any advantage an upright bike might have in the mountains is completely neutralised by the tremendous aerodynamic advantage of a recumbent. A good lowracer recumbent with a tailbox has about half the drag of a normal racing bike. Worse still, an upright rider gets almost no benefit from drafting a recumbent rider.
If the UCI legalised recumbents, a team using upright bikes wouldn't even finish the first stage of a grand tour within the time cut-off. Any team using recumbents could disappear off the front of the peloton and would be impossible to catch. In a time trial, there's simply no contest - the recumbent riders could demolish the upright riders without breaking a sweat. To neutralise that advantage, races would need to be organised exclusively in the high mountains with no appreciable amount of flat roads.
> The optimum solution is a recumbent bike...
But pro races are really all about bursts of acceleration as well as topography. Recumbents just wouldn't cut it.
Old guys going fast in a straight line by themselves in an egg-shaped container just isn't interesting to watch.
> ...which means there's no incentive to develop truly fast bikes.
It really is mostly about the training, the athletes and the teams.
In cycling, performance is result of the combination of many factors of which equipment is but one.
Historically, the UCI did use "safe design" as the metric -- they used it to exclude Graeme Obree, whose bicycle-cum-dishwashing-machine was probably safe enough for him to be riding on a closed track. That's not to say that the UCI should block innovative designs, just to note that they'll use any regulation supplied to restrict cyclists/companies/countries that end up on their naughty list.
Wind resistance increases with the square of the speed. Pros can ride at 30mph average on fast stages, where managing wind resistance is huge. A typical road bike commuter might average 15mph. All else being equal that's 1/4th the wind resistance (1/8th the power needed to overcome it), which is still big, but not the overwhelmingly important concern it is for the pros. A commuter on a utility bike who doesn't want to sweat might average only 10mph, so 1/9th the wind resistance (1/27th the power needed to overcome it). At that speed it doesn't feel so important.
For the pro, speed is the top priority, but the commuter also has to consider comfort, reliability, and visibility of other traffic (recumbents put your head lower down so it's harder for you to see over cars, and it's harder for them to see you). On heavily congested roads, e.g. central London, traffic might prevent you from going fast enough for wind resistance to be a major concern. If you commute over steep hills then reduced weight might benefit you more. But if you have a long and flat commute with light traffic, I think a super-efficient commuter bike would be valuable, and it's a pity that UCI rules discourage development of super-efficient bike technology.
EDIT: added power values as per HankB99's comment.
"Note that the power needed to push an object through a fluid increases as the cube of the velocity. A car cruising on a highway at 50 mph (80 km/h) may require only 10 horsepower (7.5 kW) to overcome aerodynamic drag, but that same car at 100 mph (160 km/h) requires 80 hp (60 kW). With a doubling of speed the drag (force) quadruples per the formula. Exerting 4 times the force over a fixed distance produces 4 times as much work. At twice the speed the work (resulting in displacement over a fixed distance) is done twice as fast. Since power is the rate of doing work, 4 times the work done in half the time requires 8 times the power."
Power output is directly felt by the rider, so it's the more relevant comparison here, and your comment is more practically useful.
Exactly, and gears and chain are horrible in this regard. The absolut vast majority barely maintains their chain which leads to a much lower efficiency and really poor longevity (no it is not hard, but apparently too hard/boring to get done).
Unless the owner is a bike enthusiast you can almost guarantee that the maintenance is abysmal.
I realized this for myself and bought a belt-driven bicycle so I wouldn't feel bad abusing my current bike. For your day-to-day bike I'm very happy with it and the maintenance benefits alone make it so worth it.
These folks have essentially turned the chain inside out and attached it to the ends of a shaft.
Look closely in that picture you can clearly see the inside of the small bearings.
And to reduce friction they're open cage which will not play well with sand and other grime.
As far as I understand it this is a mockup celebrating the intention of getting to 99, not a prototype that has achieved it. More artist's impression than product.
What's still impressive though is that the concept does away with pretty much the only actual product the company has, the pulley wheel. That is bold in a strictly economic way.
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.
I'm running a 10 speed Shimano XT cassette and an XTR derailleur on my mountain bike and it's amazing. Doesn't really make any sound and the shifting is downright amazing.
maybe you yours is damaged or sth?
Electric shifting is at this point in time more of a status symbol than an actual solution.
Not to mention the constant adjustments of cable tension as the cables stretch.
With DI2 I've not adjusted or stripped down for a good 2 years and I still have perfect shifting.
I cycle a lot (more than anybody that I know personally except for my brother) and tend do do years with cables and shifters. Cable stretch requires the occasional twist of the tensioners but that's no big deal.
I can see how for you Di2 is not a luxury though. Really curious about your mileage and other contributing factors.
The cycle-around-the-world types swear by them, they are very reliable.
Don't electric shifting solutions like Shimano's Di2 or SRAM's eTap system address this? At least I thought those systems also cover the calibration and fine tuning of the rear derailleur.
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.
Suspension does lose you a lot of energy, which is why you'll never see it on road bikes.
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).
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.
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.
The important thing with bicycles, compared with motorized transportation, is that the "engine" is still the same now as it was then, so everything is very limited by weight and efficiency. We wouldn't be able to practically use most motorcycle and automobile improvements that have come since the Model T if we were stuck with the Model T's engine power.
Disclaimer: not affiliated
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.
We use the same term for the rear end of a car and for the drive train on BMW motorcycles.
Might be usable as an electric assist drivetrain and it was sealed up.
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...
It's a roughly 50% split between users who want electronic shifting and users who don't (personally, I don't, I'm pushing more than my share of buttons when I'm not on the bike, I find the refined engineering of a mechanical groupset far more impressive than just throwing microcontrollers at the problem)
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.
(Dutch link: https://www.fietsenwinkel.nl/expert-e-bikes/nuvinci with nice cut-out picture of how it works)
Sounds interesting, can you point to some documentation?
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.
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.
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!
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.
There has also been a recent trend on the track towards larger chainrings and sprockets for a slight increase in efficiency, as the chain has to go through less of a tight radius, whilst still maintaining the same gear ratio.
After looking at the thing, it is a remarkably apt analogy, too. I wonder how long it takes to machine.
That means that they will be very efficient at shredding flesh, far more so than a normal cassette which has the fastest rotating surface closest to the wheel.
Obviously you don't want to be in contact with either if you can avoid it.
As for the spokes: that's a problem that actually reduces above a certain speed because the spokes will start to act as a plane and throw you out before you can get anything properly wedged. At intermediary speeds they are really dangerous.
That's why it is important (especially for kids) to wear proper shoes on bikes and to put spoke guards on the rear wheel where feasible.
It doesn't take much to have serious injury of toes or heel, including damage to the Achilles tendon.
At least on the other side it naturally sits with the flat side out.