"WILLIAM KITCHEN" bravely wrote to "MIKE ROSS" (30 Aug
03  01:30:00)
 --- on the heady topic of "Vehicle LED's"

 WK> So, for garden variety NiCd AA's, a C/5 charge is 120mA, C/10 is 60.
 WK> And  if your charger is smart enough to know when to quit, you can push
 WK> them  harder for short times. Not that you'd actually want your charger
 WK> sucking  up several watts of pedal power.

Indeed there's the rub: one needs to minimize pedal power. IIRC there is
about 65 watts available at maximum effort but then only in short
bursts. Assuming the sustained value is some 5 to 10 times less, then
anything that adds too much effort would be a real bother. For example a
3 watt budget for lighting doesn't bother me too much but I'd much
rather use a lot less!


 WK> But a really smart system
 WK> that can jacks  up the charging current when braking or going down hill
 WK> could be good.  Now that I think about it, it really wouldn't have to
 WK> be all that smart.  Maybe a switch on one or both brake levers, such
 WK> that the switch closes  before the brake pads make contact. Squeeze
 WK> just a little, and the charger  cranks up the current and creates a bit
 WK> of drag. Which, of course, is  usually what you want when you lightly
 WK> squeeze the brakes. This should  work for both hills and stops.
 WK> Changing your riding habits to make  longer, slower stops could improve
 WK> it a bit. Charging at a less noticeable  rate during daytime riding is
 WK> another possibility, or better yet, with a  solar cell.

Okay, I don't think solar cells are going to go on most people's bikes
(what with theft and fragility issues) but the idea is sound other than
the extra weight. Consider that an average bicycle weighs about 20 to 25
lbs so even 1lb extra makes an immediate difference at the pedals. Even
changing from a steel to magnesium kick-stand makes a noticable change!

However, I hadn't considered regenerative braking, and this I find
certainly an awesome source of power! There's a lot of power in 200 lbs
moving at 20 mph!!! If this could be easily harnessed from the braking
and then stored it would be just the thing. Unfortunately, it also
probably means adding a lot of weight in the system that recovers the
energy and stores it. It is a great idea but seem almost impossible to
execute. Too bad, I really like that kind of thinking!

On the other hand, perhaps recovering energy from braking might not be
such a bad idea for another purpose, for example as an assist in
starting the bike from a stop. One idea would be adding a flywheel
system to store the braking energy and then using it as an assist to
start up again. Pedaling could then be much easier after a stop.
But here too the system seems quite "pie in the sky" to actually make.


 WK> Of course, NiMH's are much better still.

I don't doubt there are batteries with a lot of capacity, the problem of
course is in pushing the pedals!


 WK> Heck, even carying around a 2 pound SLA battery would probably be less
 WK> work than pushing a generator. That's about the weight of the 6V, 5AH
 WK> SLA  batteries sitting on the shelf next to me. Bad power to weight
 WK> ratio.  Good power to cost ratio.

If I was going to carry a 2 lb SLA around then I'd want an electric
motor at the other end of it!!!   Speaking of which, I saw an
experimental electric scooter going through the park this past spring. I
think it was a nearby high school project. It was basically a row of
batteries under the running board and seat with a bunch of aluminium
flat stock built up from it. The wheels were about 6 inches in diameter
and the back wheel had a large gear and chain going to the motor
sprocket. It moved at a very nice clip. It was amazingly quiet and
seemed to take inclines at a sustained rate. Electric motors are good at
supplying power to a load as it demands.

 Mike
 ****

... I worked hard to attach the electrodes to it.
--- Blue Wave/DOS v2.30