On Aug 28, 2014, at 10:28 AM, Michael Ross via EV <ev@lists.evdl.org> wrote:
> 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. I think the only thing that I'd add to your analysis is that, for motorcycles, modern belts are almost as efficient as a chain and require much less attention. For racing where you might be rebuilding the whole engine every few hundred (or even few dozen) miles, that's not even on your radar, but the extra few percent of performance will make the difference between winning and coming in dead last. But for daily riding, you're not going to notice the efficiency losses associated with a chain, whereas the added mess and maintenance of a chain can turn into a chore that makes the bike a burdensome hassle. There's a reason Harley went and stayed with belt drives. > 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. For the foreseeable future, chains are the only option that even theoretically make sense for human-powered vehicles. There is, however, an interesting potential possibility should we ever get the generate => store => motor efficiency into the 90% range: hybrid velomobiles. For those who don't know, velomobiles are fully-faired human-powered vehicles, typically with a tadpole trike configuration. If your cruising speed on a road bike is in the 20 MPH range, your cruising speed in an high-end velo is going to be in the mid 30s. The Tour de France riders could keep up with freeway traffic in one. Add a half-kilowatt electric motor and so could the 20 MPH road bike rider -- and you can buy such an electrified machine today for under $20k. But here's where things get interesting, if we assume that magical 90%+ efficient electric generator / battery / motor drivetrain. Humans have their own peak efficiency range for both speed of pedaling and exertion amount, just as with ICE motors. And velos don't need to be balanced at a stop. What that means is that you could get in the velo, start pedaling at your optimum efficiency range regardless of how fast the bike is going, and use hand controls for driving. When you come to an hill, you don't change your pedaling; you just drain the battery faster and / or slow down going up, and either regen with constant speed or speed up going back down. When you come to a stop, you keep pedaling; if you need a break from pedaling, there's no need to stop driving. Even if the drivetrain isn't as efficient as a chain, if it's close, all the rest of the advantages would add up to better performance all the way 'round. Cheers, b& -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 801 bytes Desc: Message signed with OpenPGP using GPGMail URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140828/3be51515/attachment.pgp> _______________________________________________ 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)
