[ausev] Question for the EV Nerds

[lyle sloan]

Most of what Chris has said is right on the money.  I like to give a blanket response as far as the debate to using gears/transmission for a bike:

Reasons to use a transmission: 
a). per physics, it takes less amps to get the same motor-to-wheel torque with the right gearing 
b). single gears reach an RPM or max speed limit due to voltage of the pack (for a DC motor) 
c). single gears require a delicate selection of choosing either not enough low end torque before reaching topspeed (slower take off), or more
low end torque with a lower top speed 
d). performance selection for driving needs (i.e. choose the correct
gear for going uphills or speed) 
e). a clutch is usually included for freewheeling 
f). when geared for a higher top speed and during heavy acceleration, single gears have the motors (especially pancake motors) in their heat limits longer (which has been known to cause them to burn out)

On the opposite end, reasons not to use a transmission: 
a). transmissions add rotating mass and weight reducing efficiency 
b). trannys use up the limited space on a bike for batteries 
c). trannys have to be found or modified to work because the ones that come with the bike arent designed for the electric motor (or money) 
d). single gearing is simpler 
e). greater speed can be done simply by adding more batts and battery switching (for a DC motor) 
f). more torque can be gained by going to a larger motor or using two
motors 

Ultimately, it is up to the builder and his pocketbook.

Far as in the Texas area, there is http://poormansev.com Jack Knopf north of Austin and Jon Anderson from San Antonio http://www.youtube.com/watch?v=phodjMK2iVE


--- On Wed, 6/4/08, Chris Robison wrote:

> Tom Burbridge wrote:
> > Greetings,
> > 
> > I'm about to pull the motor off my Honda NH 450
> and add a 96v pancake motor.
> > 
> > My question is:
> > 
> > Should I go direct to chain or through the
> transmission?
> 
> Most motorcycle conversions tend to do without the
> transmission. In many 
> cases this is partly because the transmission is difficult
> to separate 
> or use separately (unlike on a harley davidson, where
> it's already a 
> discrete unit). Going without the transmission does imply a
> somewhat 
> delicate compromise between acceleration and top speed;
> you'll 
> definitely need a larger rear sprocket and a good bit of
> calculation to 
> figure out how many teeth to put on it. You may need some
> trial and 
> error as well, with a couple different attempts before you
> find a 
> sprocket ratio that gives you the best performance without
> limiting your 
> top speed, or acceptable top speed without burning up your
> motor.
> 
> What motor are you using?  If it's a permag or shunt
> motor, what's the 
> RPM at 96V? What is the continuous horsepower rating on the
> motor? 
> Figures like these will be important in both the
> transmission decision, 
> and the design.
> 
> If you can keep and use the transmission, consider doing
> so, but realize 
> that the volume it takes up may be useful for putting in
> another battery 
> or two, which would yield better range. Motorcycle
> conversions using 
> lead batteries are difficult, primarily due to finding ways
> to fit 
> enough energy storage to make the bike useful.
> 
> I don't know of anyone local who's completed a
> successful motorcycle 
> conversion, though I do know one unfortunate fellow
> who's blown up a 
> couple Eteks trying. :-) The best online resource I'm
> aware of is 
> http://electricmotorcycles.net. Unfortunately at the
> moment, it's 
> apparently been taken down for maintenance...
> 
>    --chris
> 
> 
> 
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