About 28 seconds in

[video]http://www.youtube.com/watch?feature=player_detailpage&v=wOB-KciTjvo[/video]

That looks like a poly V auxiliary drive belt, not a toothed cam belt.
Surely that would slip under load.

I suspect as a basic city bike it’d be ok to pootle about on

Hard to tell from the video, looked like a convex sprocket, the belt to me looked like it was slightly curved round in profile.
No idea how much tension it’s under.

I would ride it round town, would be uneasy about out of the saddle stomping up a hill.
be interesting to see how it coped with greasy grimey city road spray getting in there with no drive teeth.

I assume it works as they had a web address and you can order one. Be sticking with chains 🙂

It wouldn’t work. The tension needed to stop it slipping when wet would be over-stretching it and would stress the bearings. You need a toothed belt, which is taut enough not to jump but still loose enough not to put stress on the other components.

65A alternators aren’t uncommon, and that’s over 700W, so for everything other than sprints it’d be fine.

They’ve got a website too. http://bicycledbikes.com/

It looks like more of an art project than a serious business idea.
That seat post clamp for example, it must take an hour or so to make when you could buy one for £2, just to recycle 50g of metal.
And the frame tubes. I don’t know what part of a car they came from.

A 12v 90a alternator generates about 1000w, about the same as a very fit cyclist, so in theory, the belt would grip.
Unlike a multi cylinder engine, a cyclist generates power in pulses.
Even with a spring loaded tensioner, I reckon it would slip when pedalling hard.

surely a cambelt would be better?

And naturally geared to 2:1, the single speeders favourite. 😀

looking at power is wrong, it is torque that matters.

power = T * Omega = torque x rotational velocity

so feet are not spiining at 3000rpm liek a car engine producing 1kw throught he alternator.

lets sayy 100 rpm means th eload ont eh belt is 30x higher. if you stamp th epedals from rest it would be even more, so it might transfer power, but it would slip in the process.

which strictly is exactly what a ‘fan belt’ does.

a toothed belt prevent slip as it it not relyign on friction to the same degree. hence being used where ‘timing’ matters, liek a cam belt.

a fan belt relies on friction to generate grip and needs tension to creat friction. a toothed belt only needs tension to prevent it jumping, it doesn stretch int he same way so the ‘tension’ is signifcantly less.

if you could get your head round the feelign of slip, and the loss of energy int he process, then a ‘fan belt’ would work on a bike, but it would not be efficient and would require large bearings to cope with the tension loads.