Re: EV kits on S.F.Craigslist

cowtown@... wrote:
> An 800A contactor and "Regen braking with down shifting" and  
> "remanufactured and modified jet fighter plane generator used as  
> motor" sounds like an EV made in the 70's that avoids using that same  
> era's more silicon-heavy controls (SCRs, Triodes, etc). Any idea how  
> smoothly a VW-with-jet-starter/generator conversion can be driven in  
> everyday use, how efficiently they run when compared to current motors  
> and PWM controllers, and what is their comparative durability?

The 1970's aircraft starter-generators are still state-of-the-art today;
DC motor technology has hardly moved. They have huge strong commutators,
class H insulation, interpoles and pole facing windings, high speed
bearings, are banded and balanced for high RPM, etc. They are excellent
for regenerative braking.

However, they were optimized to be light, not efficient. Compared to a
modern series DC traction motor, The aircraft starter-generator is about
half the weight but only 75% efficient versus 85%. They also didn't care
about noise; these things scream like a giant vacuum cleaner.

Smoothness isn't a characteristic of the motor; it's a characteristic of
the controller.

> Would a "cutting-edge' Curtis SepEx controller, say 600A in the 36-84V  
> range, make this older style conversion any more efficient, or would  
> it also need a motor more specific to the job?

If the old one used an SCR controller, a Curtis or other modern
controller will be more efficient. The efficiency of the motor itself
won't change.

The main limitations of these old unit are:

  - lower efficiency (reduces range by 10% or so)
  - hard to use shaft (odd spines, no support bearing)
  - need a lot of cooling (due to lower efficiency, no internal fan)
  - too small for a full-size EV (only suited to very small light cars)
--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in    --    Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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