Hi Lee, Chains are very efficient, speed doesn't matter. If I had to guess, less tension in it would reduce friction. I spent a lot of time on a mailing list called hardcor bicycle science once. They would do all manner of experiments to prove and disprove stuff like this. The friction in a chain is almost immeasurable.
If you look to motorcycles - there is empirical evidence - the highest performance bikes have chains. They do dyno testing and will do whatever they can to increase how far a tank of gas goes, or to improve acceleration and top speed. A gear set can't come close. Bevel gears suck. Belts lose a lot (well, more anyway) to internal heating of the rubber and carcass/fabric. Chains are the way to go. Springs have to distribute tension through a lot of material to store much energy without breaking or taking plastic deformation, and they don't return the energy in a constant manner. They do get hot if you work them constantly. Flywheels are more commonly tried for this sort of thing. There is a logical conundrum with human power - the far best efficiency comes from simply using your legs to move the machine - storing that energy is always a big loser. If you can scavenge it somehow once it has been applied - you can get a little back, but more often the scavenging method is heavy and complicated. If you waste your biological energy doing something else besides going forward, you have a comparative loss. On Thu, Aug 28, 2014 at 1:05 PM, Lee Hart via EV <[email protected]> wrote: > From: Chris Tromley > >Not liking the efficiency hit, but still an interesting idea. > > Like any hybrid, you lose efficiency at the peak; but regain it during > other modes of operation. If you spend enough time in these other modes, > then your overall efficiency improves. > > I'm no expert, but I suspect a chain's efficiency is very high only at > full load. At light load, it has so many moving parts (all of them with > sleeve bearings) that I suspect its efficiency becomes quite low. > > It is possible to design electric motors and generators to have a very > wide efficiency band. PM motors have high peak efficiency, but low > light-load efficiency because they run at "full field" all the time. A > wound-field motor loses a bit at full load (a couple percent due to field > power), but gains at light load. A wound field DC or AC synchronous > motor/generator might therefore be the best option. > > Brainstorming... I've always wondered if a human-spring hybrid might have > merit. Springs don't store much energy, but can be an extremely efficient > way to store small amounts of power and get virtually all of it back. Wind > up the spring going downhill, and use the stored energy to go back up. :-) > > -- > Excellence does not require perfection. -- Henry James > -- > Lee A. Hart http://www.sunrise-ev.com/controllers.htm now includes the GE > EV-1 > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison <http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140828/17a1aa48/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
