[kibbee]

Hello, I am considering a Saab 900 for an EV conversion and am just in beginning stages of figuring out how to implement it. Can someone please tell me the vertical measurement between the engine mount surface (on top of the transmission) and the center of the input shaft to the chain drive? I am envisioning an electric motor sitting up there, but I am not sure if there is enough room. There are other considerations too, but I thought I'd start with the space issue. Thanks so much.

 

[spydergear]

I know someone who has an electric-converted Corvair Rampside. He has even gone to the expense of installing lithium-ion batteries. He has broken at least two transaxles that I know about. If you were to use the available torque that an electric motor exerts at zero RPM, I would wonder if the SAAB gearbox would fare any better than my friend's truck.

 

[jvanabra]

The distance is about 3".

I too would be concerned about torque output. You would definitely want to limit it to 100 lb ft or so to get any sort of longevity IMHO.

 

[02Pilot]

Why mess with a transmission at all? I'd be much more inclined to drive the axles straight off the motors. You don't really need gears, and you shouldn't need a diff if you can run independent motors for each wheel.

 

[peva]

Why not put a whole new electric trans-axle in at the rear. Leave the front and engine/transmission alone.

 

[jvanabra]

Why mess with a transmission at all? I'd be much more inclined to drive the axles straight off the motors. You don't really need gears, and you shouldn't need a diff if you can run independent motors for each wheel.

Conventionally speaking, that's a LOT more engineering than just putting an AC motor where an IC engine was. The "common" electric conversion is basically a bell housing adapter which bolts an AC motor to an existing (usually RWD) transmission... just stick the transmission in 3rd or 4th and leave it there forever, but use the factory differential so the car turns properly.

You need a "differential" (whether physical or logical) so you can turn the car. You would need some advanced controls for motor-per-wheel configuration in order to properly steer... and that'd be exacerbated on the steering wheels I'd think.

 

[PabloRock]

Saw a BMW e30 converted using tesla stuff. (maybe he had money to burn). Batteries in the trunk.

 

[02Pilot]

Conventionally speaking, that's a LOT more engineering than just putting an AC motor where an IC engine was. The "common" electric conversion is basically a bell housing adapter which bolts an AC motor to an existing (usually RWD) transmission... just stick the transmission in 3rd or 4th and leave it there forever, but use the factory differential so the car turns properly.

You need a "differential" (whether physical or logical) so you can turn the car. You would need some advanced controls for motor-per-wheel configuration in order to properly steer... and that'd be exacerbated on the steering wheels I'd think.

It's all true, but it's only a massive engineering problem if you're building from scratch. Personally, I'd be looking for a wrecked hybrid or electric in a yard and grabbing the guts from there rather than trying to build something myself, especially given the fragility of the Saab transmission and the instant torque of electric motors.

 

[Jim Mesthene]

Using a large band saw, cut the transmission off the transaxle case to make a cradle for the motor (an automatic already has a sealed final drive). Then mate the motor shaft to a shortened differential/mainshaft at the pinion bearing housing (sort of making the differential a 'nosepiece' on the motor).

Voila! Robert's your father's brother!
Ideal weight distribution too.

 

[jvanabra]

Like. ;ol;

 

[02Pilot]

Yeah, Jim's solution does seem a very logical way to approach the problem.