> >Using the brakes on the front wheel only and the mass of the 
> rider and 
> >bike behind it to compress a spring (hinged frame with coil spring, 
> >flexing frame with leaf spring, telescoping frame with air 
> spring) and 
> >then the standard Sprague clutch on the rear wheel to prevent the 
> >release of that energy until the front brakes are released. No 
> >additional components, easy to control via the front brake.
> 
> James,
> 
> What I meant was how would you control the transfer of energy 
> into the spring?  A simple clutch gives you either none or 
> full regenerative braking.  Ideally you would have some kind 
> of variable ratio drive so you could actually control how 
> quickly you slow down.  If the system is permanently geared 
> then in many situations it will either be too little and you 
> have to fall back on normal friction brakes, or too much.  
> And of course you would need to include a mechanism to 
> prevent too much energy being input, i.e. disconnect 
> regenerative brakes once the spring is wound up to maximum.
> 
> I know when you have a hammer everything looks like a nail, 
> but I reckon this application would only be practical using 
> electrical storage.  Springs, compressed gas, flywheels etc. 
> are all too bulky/heavy/dangerous.  The above problems are 
> all overcome by a relatively simple electronic control system.
> 
> Regards
> 
> Mike


Hopefully all of the mechanical systems I listed would require minimal
additional weight by re-using parts of the existing bike or replacing
existing pieces with parts that could serve dual function. E.g. replace part
of the frame with a leaf spring so that the frame itself flexes and also
holds the bike together. An air motor is light and the bike frame could be
used as the storage tank.

It would only work at full braking, but would be combined with electric
regenerative brakes so that there would be two levels available. Some energy
would still be lost to frictional braking, but something is better than
nothing. The point here is that batteries can't be recharged at the levels
that rapid braking generates. The mechanical stuff is to be an addition to
make up the difference. 

Having said all that, super caps are looking good, abet expensive, and I
totally agree that an electrical system would be preferable.

---
James.
 

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