Electric GS500

[ohgood]

IIRC, it said front sprocket was 11T

Wow, if that's -just- a 10 ft/lb torque motor, that thing is a freaking wheelie machine with those cogs ! Hope the variable pot is sensitive enough to NOT flip it every time you take off !

[GeeP]

and what is it with that huge rear sprocket? 

Speed reduction.  He likely needs a decent reduction to get into the motor's sweet spot, much more important with DC motors.

Correct me if I'm wrong, but don't DC and AC motors create ALL of their available torque @ 1 to infinity rpms ?

If so, then the big rear sprocket is for chain wrap, and I'd bet there was a largish front sprocket also. You know, 50% wrap or whatever to keep things working well.

A 'lectric gs would rock. Light bike, good handling, good ergos for commuting, and the cost per fillup (plus assuming a replacement battery at some point worked in) of around $.30 each ?

Someday, capacitors will have a major storage / charging bump, and we'll all enjoy the smooth immediate torque of electric motors. Imagine a leasing agreement with 'gas' stations where you pull in, and swap out your battery for a charged one in 2 minutes, for $10. Awesome. Never happen in the US though, sadly

DC motors generate peak torque at stall, yes.  Torque falls off as speed increases, until net torque output is zero at no-load speed.  Therefore, gearing is important.  Too much of a reduction and it's a wheelie monster with little top speed.  To little reduction and it's a fast bike, but slow to get there.



AC motors are somewhat the opposite.  An AC motor generates torque as a function of rotor slip.  In other words, up to a point, the more the rotor lags behind the rotating field, the more torque is generated.  That point is called the Break Down Torque.  Increasing the load beyond that point will cause a rapid loss of rotor speed (and therefore power).

http://www.tpub.com/content/doe/h1011v4/css/h1011v4_27.htm

The interesting part about AC motors is that if you vary the frequency to the motor (thus regulating the slip) you can power a motor with a perfectly flat torque curve from nearly 0 to 120% rated output or beyond.  The surge ratings can be significantly higher.

Locomotive manufacturers have known this for years.  The best measure of locomotive traction efficiency is adhesion.  In other words, how much of the locomotive's weight is turned into tractive effort.  A 100,000 lb locomotive developing 20,000 lbs of tractive effort has a factor of adhesion of .2, or 20% of the locomotive's weight.  19% to 22% is common for DC traction.  However, a locomotive operating with AC traction motors can have factors of adhesion of up to 40%, mainly due to the increased motor control afforded by AC control.

What does that mean for motorcycles?  Imagine a bike with smooth, effortless power.  ALL of that power is available ALL the time.  In fact, the variable frequency drive will need to have a ramp time, otherwise the machine will wheelie instantly.  Traction control could be incorporated very easily with existing industrial VFDs, regulating wheel slip even during cornering.  Rear braking would be dynamic with traction control (no more locked rears, ever).

Oh, yeah.  The motor and control should outlast the frame.  Just grease the bearings every 10,000 hours of operation. 

[starwalt]

Nuts. The dude beat me to it. He is running the same motor I planned to put on my conversion.

After running numbers on weight and using one of the EMoto spreadsheet out in the EV community, I decided the GS was too heavy to get any range.

Weight, wind resistance, and system friction  are the killers of EV performance. I am considering a composite GS chassis...but then it really wouldn't be a GS anymore would it?

[scottpA_GS]

Nuts. The dude beat me to it. He is running the same motor I planned to put on my conversion.

After running numbers on weight and using one of the EMoto spreadsheet out in the EV community, I decided the GS was too heavy to get any range.

Weight, wind resistance, and system friction  are the killers of EV performance. I am considering a composite GS chassis...but then it really wouldn't be a GS anymore would it?

Thats awesome... You plan on building an electric bike?  Be sure and post your progress 

[manofthefield]

I am considering a composite GS chassis...but then it really wouldn't be a GS anymore would it?

I think it would be if the composite chassis was molded in the shape of the GS frame

[natedawg120]

I am considering a composite GS chassis...but then it really wouldn't be a GS anymore would it?

I think it would be if the composite chassis was molded in the shape of the GS frame

yeah thats close enough for me