> What I meant was how would you control the transfer of energy into 
> the spring?

Pawl and ratchet :-)
Apply brakes in bursts.
Spring is compressed and then trapped by pawl.
Debrake and start again.
May have some operational issues :-)



    RM 

-- 
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist