Saint Sheldon says “just use a chain case”, and as usual, he’s spot on:
Shaft drive was briefly popular around 1900, and occasional attempts are made to revive the design. Unfortunately, shaft drive turns out to have more problems than advantages.
A shaft drive requires heavier frame construction around the bevel gears to maintain their precise alignment under load. The drive system is heavier and less efficient than a good chain drive.
For reasons of clearance, the bevel gears of a shaft drive bicycle must be considerably smaller than the typical sprockets used with a chain drive. The smaller size of the gears causes an increase in the stresses on the whole support system for the shaft. This problem is exacerbated because the stresses from the shaft drive are not perpendicular the triangulated structure of a bicycle frame, and so are not well-resisted. .
Most of the advantages touted by proponents of shaft drive are only advantages compared with open-chain, derailer gear systems. Many proponents of shaft drive use specious (if not dishonest) arguments "comparing" shaft drive systems with derailer gear systems. Any such comparisons are meaningless, it's like comparing apples and locomotives.
Shaft drive proponents also often compare sealed, enclosed shaft drive systems with open, exposed chain drive systems. This is also a misleading comparison. All of the advantages claimed for shaft drive can be realized by the use of a chain case.
Shaft-driven motorcycles are a whole other story.
Or are you suggesting we use hub gears? Because those are significantly lower efficiency. Only Rohloff is really competitive but it's still around a 5% efficiency loss compared to derailleurs.
They claim 99.2% efficiency in the video over 97% for the top-performing chain driven versions. Do you have any data on chain driven systems that are better than what they compared it to now?
For 99% of cyclists, though, it doesn't matter. The overwhelming part of your work goes into air resistance, then rolling resistance at lower speeds, and probably the chain in last place.
In the last few seconds of video the mechanism can be heard -- oh boy, it is loud. The pawl in bikes can range from nearly silent to annoying, but this one seems to be even worse.
What matters is clean look. Chains are dirty and look dangerous. Good bikes (like Dutch omafiets) cover the chain, but if scaled manufacturing cost of this system is $30 extra, people would pick this one.
Carbon belt drives are an alternative, but are not shiftable without internal gears like a Rohloff hub or Pinion gearbox/bottom bracket which are expensive and heavy, and regarding the Pinion, needs a proprietary bottom bracket built into the bicycle's frame. Belt drives are more much more expensive than chains, and also require a special frame, but they last much longer, and require virtually no maintenance. They are not nearly as efficient though which is why they aren't found on track bikes. Belt drives are great for riders that enjoy just riding along and want to invest in a nice maintenance-free alternative.
When Driven reaches production I would bet that it will go the way of the belt drive. It will have incredible improvements over a chain, but will be very expensive. I wouldn't be surprised if the total cost of the crankset, driveshaft, cog, and shifters are north of $3000 or more, not including the price of the wheel or frame. Pricing out almost everyone, except for the select few that find the improvements worth it. It won't be released until it is able to be raced professionally and I definitely think it will be seen in races where seconds matter.
It won't replace the chain as we know it, but this alternative will be on certain bikes owned by people that care about its benefits.
I believe it can replace the chain in all but the lowest bikes. It will start expensive, but so did many other technologies we now see on common priced bikes.
It's not just friction efficiency, but weight and other factors, too.
The split pinion reminds me a bit of a DCT. Especially when they put the cover on.
For some reason there's a tendency to assume that unusual things in the bike world are crazy new inventions.
Both shaft and belt drives have benefits fir the consumer, but performance isn’t one of them. It’s probably similar bicycles.
So though shaft-driven bicycles most certainly exist, I would argue that they are the dictionary definition of “uncommon”.
I would guess this maintains its efficiency advantages only in very limited torque ranges and have overall power limitations that normal drivetrains don't.
For general transportation, electric bikes are the real revolution.
These bikes stay chained outside overnight for years with minimal maintenance.
But every now and then there are innovations that actually take hold. For example, the slant parallelogram dérailleur, hydraulic disk brakes, suspension (for mountain bikes), and recently single narrow-wide front chain rings. We shall see how well this drivetrain goes.
Except we have in the form of recumbent bicycles which have a huge aerodynamic advantage but they were banned in the 30s by making rules to enforce the frame dimensions.
Recumbent bikes hold the world land speed record on a bicycle if the definition of a bicycle is "2 wheeled muscle powered vehicle". For example the flying 200m speed record is 133km/h (flying start, flat ground, 1.66m/s tail wind max). 1h distance record is 90km while for normal bikes it is 55km etc.
Basically rules stifle a lot of innovation in the cycling world. Most pro bikes are too light to race legally so they have to add led weights. Strict rules about handlebars so you cannot get into a good aero position easily etc.
But the general consumer most likely doesn't want to spend too much money on a bicycle and recumbents tend to be a bit more expensive compared to uprights.
Todd Reichert achieved over 144km/h in a Sep 2016 record (almost flat; average down-slope under 2/3 %)
UCI regulations are there to make a clear separation between sport and tech. given the latest advancements in engineering it's possible to render the athletic abilities of a person irrelevant. power to weight ratio is an important stat in cycling and there is serious physical preparation involved in the process of dropping a few hundred grams in weight before a competition. now imagine that instead of that you get the latest innovation in carbon frame design and drop that weight from the bike. tech wins. and that's not the purpose of sport competitions. F1 has similar regulations for the exact same reason.
also, these regulations address health and safety. some aero positions can affect a rider's stability and, in turn, can affect the security of other riders.
Lots of improvements have been made on this. Google 'recumbent bike'. I drive past a guy most mornings in one of these things . He is driving that thing summer and winter, rain or shine.
For the normal consumer, probably more about price than anything else, unless it enables better electric/motors, etc.
This way just be the bubble that I live in, but I think the average cyclist that I know cares more about tech and marginal performance rather than price. New (performance) bikes commonly sell for thousands of dollars. It's not a world that seems especially price sensitive.
We've had bikes that can go over 100 km/h since decades and they aren't legal in biking sports because of these rules so bikers in sports only go about half that fast.
This kind of device works for years on a small battery, signaling every rotation of your wheel to your phone as you cycle:
I used to ride a cheap bike (Liv Alight 3), but after replacing 3 wheels it was cheaper to buy a nicer bike. Tourney has become a swear word in our house. Lately I've been riding my Catrike Expedition which is a blast, but chain and gear maintenance is still a problem.
I am not a fan of Patents, especially software patents and ones that are deliberately filed for malicious, anti-competitive measures.
When a company truly innovates, they deserve the prize of a patent. It appears that they've done so, investors lurking around or not.
This piece of gear system is a mix of central shaft(that we see in trucks + gear + that cut-in-half gear tooth)
If we split it into three individual item, then it is a three different patented item. Put together you get a new patent? Come on!
tl;dr: interesting and shows promise, still more work to do.
edit: don't be scared by the not-a-paywall greyed out text and box.
On single-speed bikes and common derailleur type multi-speed bikes (yes, even with freewheeling, but I assume even more without it) there's a very direct linkage between pedaling and movement. You start moving pretty much the instant you put pressure on the pedals.
I've noticed on some hub-gear bicycles there's a significant amount of slack where you have to pedal without resistance for at least 1/8 of a revolution until the drive mechanism kicks in. This is very frustrating to me (again, I'm sure it's only me...) and completely disrupts the suspense of disbelief I otherwise can conjure, which seems to be what allows me to get that freedom feeling almost like I'm flying. The lack of feedback for that fraction of a second yanks me straight out of the flow of navigating traffic with the bike as an extension of my body and reminds me sternly that I am sitting on a very-separate-from-my-body mechanical horse, some aspects of which are very much not in my control.
That sense of freedom is definitely one of the major reasons I use the bicycle as my primary means of transportation.
Sorry, very long rant about something very unspecific but vaguely related.
For amateurs doing races, it's the same. For the huge majority of amateurs it depends on cost, durability and ease of maintenance. For everybody else, it's only the cost.
I ride a recumbent tricycle, and an interesting complaint from my dad when we were discussing why recumbent trikes and velomobiles aren’t more widespread is that the design is unweildy, that the end result doesn’t look polished; so we discussed ways that you could make it neater. The chain on recumbent trikes goes from the very front to the back of the vehicle, so it’s a long, subjectively unsightly thing. Something like the this Driven shaft drive would be quite unsuitable for a trike due to the length of the shafts that would be required, and the resulting torsion.
So then, we wondered, what would it be like if you replaced the entire drivetrain with an electric drivetrain? Pedals at the front would drive a generator, which would pass power through slim wires hidden inside the frame or similar, to a motor at the back. Much neater, visually if in no other way. This would fit in very nicely with making it an e-bike, too: precise legislation wording could be problematic, but your 200W or 250W or whatever would be added to whatever power you generated by pedalling. And by being a fully-electric drivetrain, efficiency would be improved on the electric assist. (Probably similar to the benefits that I understand going full-electric on hybrid car drivetrains can offer.)
I’m not deeply familiar with the efficiencies involved, but my impression from light research is that regular chain drives start out at up to 97% but often operate at figures closer to 80–85% due to wear and lack of maintenance; and a full electric drivetrain could be over 90% efficient, though it’d be more likely to be around 80%. (Remember, we’re not getting a battery involved at this point, so no losses on that.) Perhaps such a drive would be on par with a typical chain drive for efficiency, though less than a well-maintained one; but it could provide improvements in efficiency in other areas (electric assist and foot-to-bike power transference).
I believe that less maintenance would be required, and it’d the complaint of the dirtiness of bike chains too. Heavier parts and more expensive, unless you were going e-bike already in which case it may be lighter and cheaper, which would become a much more obvious thing to do for such a bike.
It’s interesting to think about. But I doubt I’ll ever do any practical experimentation on the idea, because my list of projects I’d love to work on is already more than thirty years long (and getting longer each year), and this sits a fair way back on it.
Hydraulics would also be interesting to experiment with. https://en.wikipedia.org/wiki/Chainless_bicycle is a good page to start on for learning about all these things.
On a bicycle, the wiring would certainly be easy and considerably lighter than shafts, chains or hydraulics. You would take a hit on efficiency as pedaling force would have to be converted to electricity and then back to motion, but generators and motors are pretty good these days. Weight could be an issue, but again the developments in hub motors have seen the weight come down a lot to the point that your idea seems viable.
I'm not saying more range from the same battery would be worthless, just that the ranges they already offer are plenty marketable.
I also wonder about the efficiency of a small (tiny!), slow generator.
A substantial art of this thought experiment is about designing a delightful product. As my dad said to me: if Apple were designing a bicycle or tricycle or velomobile or similar, what would it be like? We both agreed that there wouldn’t be an exposed chain, for starters, and I suspect that they’d at least try to do away with the chain altogether, and they’d care about efficiencies if they went down this path.