In the video above, Tom Stanton shows a valid experiment in regenerative braking. Admittedly, his attempt doesn’t present spectacular results, but he’s on an interesting track. Continuing engineering in endeavors like this can potentially yield excellent results.
The concept of a flywheel does present some issues. First, there’s the weight. That can be considerably reduced by using a lighter flywheel but at much greater speeds. For instance, dentist drills can spin at up to 420,000 revolutions per minute. Of course, a large flywheel at that speed would blow up from centrifugal force.
Then there’s the gyroscopic effect. An angle applied to a spinning wheel will push the wheel at a 90-degree angle. With a large, fast flywheel, you would certainly notice the effect in steering the bike.
More than likely, the wave of the future will be regenerative braking energy stored in lithium-ion batteries.
As you’ll hear in the video, his gears are particularly noisy. That would not be a problem in a production model, in which the gear teeth would be cut at an angle.
A side note: When you hear most manual transmission cars in reverse, they seem to whine. That’s because the reverse gears are straight-cut, whereas the forward gears all have angled teeth.
With some internally-geared bicycle hubs, you can ever so slightly feel a ‘whirr-whirr’ effect. That’s due to straight-cut planetary gears in the hub.
The Rholoff Speedhub – 14 Speeds