The above had popped up in another thread. Well, call me stupid, but they make no sense to me. The demonstration video clips offered, show only that a bicycle with one of these attached can in fact actually still move (about as useful as showing that a bike can move with baseball cards slapping against the spokes). The photos show only various large disks for the hubs - no exploded views, no examples of actual gear range obtained with either device, or how they might work. In fact, there is absolutely no technical data offered. These devices could weigh 20 pounds, and simply be cast iron multi-speed hubs. It is stated that one device is "infinitely adjustable, incrementally adjusts to exact output ratios" ~ what does that mean? Sounds like just shifting a hub gear. And, one prototype has been in development for 30 years now... and is (still) looking for investors.

There are derailleur driven auto-adjusting bikes like the "Autobike" and the "Landrider" which seem to make more sense than these systems - at least for someone who is too spastic to shift an indexed gear manually.

The only logical, advanced, hub gear I've ever seen which makes sense to my simple mind, at least, is the Rohloff "Speedhub" - a 14-spd internally geared hub transmission system. It has gears spaced 13% apart, covering the full range of a typical MTB system, can be shifted up or down, on the fly, while climbing or descending at speed and under full torque. It shifts with a single gripshifter. It weighs the equivalent of perhaps an entire XTR drive system who's hub, derailleurs, cables, and various parts would all be replaced with this simple mechanism. It also costs $1,000.

While I love the concept of a revolutionary new drive system, it is sad that two home-brewed gadgets like the ones linked above can't seem to offer anything substantial - only claims, dreams, and a lot of very suspicious wording, at best.

PLEASE, please, please if anyone knows anything at all about the above linked projects, or of any other similar concepts which they have actually seen effectively working- and doing so better than any tangible bike technologies currently operating, do clue me in.

Honestly, I love the fantasy of climbing over the Alps with a fully loaded touring bike which has truly infinitely variable gears to keep me and 50 pounds of attached gear, spinning effortlessly at a constant 80 rpms both up and down the mountain passes, but the technology seems to have either wizzed past me... or,... maybe it just ain't out there.

I am truly a dreamer... but also a skeptic.

There are automobiles with CVTs. For bicycles the efficiency, weight, complexity are issues. Probably the biggest issue is need. Really, 27 or 30 ratios are plenty. If you really must have more 90 isn't too hard to get to. (SRAM dual-drive hub with 3x10 drivetrain). You can spin at 80 RPM now, you just may have to go a bit slower than you'd like!

The biggest advantage to a CVT, whether it's car, bike or snowmobile is that if you have a narrow powerband for your motor, you can keep the motor constantly in it's powerband.

For a bike, it would be efficient, but I don't think that the slight increase in efficiency would outweigh the complexity, cost and weight issues.

Az

Every motor scooter you see not more than about 5 years old has a CVT. It keeps the small engine used at a constant RPM so the engine is running at its most efficient RPM all the time. It also eliminated manual gear shifting so women purchase and ride them. They're also starting to show up in automobiles designed for maximum fuel economy. At this time a bicycle CVT costs considerably more than a derailleur system but this is about to change. The current patents on bicycle CVT systems are due to expire so everyone is waiting for that to happen. Hence, no investment in the company's that developed them. Watch the Chinese mass produce them and link them to the pedals with shaft drive eliminating the chain entirely. This will be good for comfort and MTB bikes but road bikes will continue to use a chain just like crotch rocket motorcycles. You will also see them retain a front derailleur and multiple chain rings on touring bicycles for mega range drive systems. The internal workings are pretty simple. Picture two cones or funnels placed side by side linked with rollers that move up and down between the angled surfaces. Moving the rollers up and down changes the ratio between input and output with a ratio of about 3 to 1. A considerable range of adjustment! The cones and rollers may be aluminum or if weight is a consideration and cost is no problem titanium may be used and the weight need be no more than the traditional hub, cassette, and chain. Index shifting and adjustments are a thing of the past. Simply rotating the shifter and pulling the rollers up and down the cones provides the infinite ratio changes. Just think of a friction shifter where you need never "find" the required cog. Here is a link to everything you ever wanted to know about the CVT.
https://www.gizmology.net/cvt.htm

Here is the continually updated commercial resource site for CVT systems.
https://cvt.com.sapo.pt/toc_en.htm

The conventional roller chain and cogs has greater mechanical efficiency than the CVT. Even if one demands a fairly tight ratiometric progression (I prefer 6 or 7%), a conventional modern derailleur system (2x9 or 2x10 for racing and light touring; 3x9 for mountains or loaded touring) provides more than adequate range.

I am even less enthused about any sort of automatic transmission for a bicycle, because I know what gear ratio I need at any given time, and I don't want any nasty surprises while riding. (All of my cars do have automatics, but that's an entirely different application.)

Now that I think about it, I did see one motorless bicycle climbing over steep alpine roads at 20-25 mph while the cranks were spinnning at over 90 RPM. It was underneath Lance Armstrong.