Originally Posted by henrykeultjes
3. A pancake configuration is more torqy
10. The pancake configuration sits directly on top of the pinion shaft to the ring-gear eliminating the typical EV 90 degree gearing from the motor to the differential. Gearing could be inserted there, if desirable.
12. The pancake configuration on top of the differential allows the SRMG to be bolted to the differential through the bottom of the enclosed compartment that holds the SRMG and controller thus physically separated from the rest of the drive-train.
Yes, a "pancake" or large-diameter (and axially short) motor design is suitable for high-torque low-speed applications. With a motor having these characteristics, the reduction gearing can be a single step, such as the pinion and ring gears of a traditional final drive unit.
- There is no connection between the SRM type of motor and a pancake configuration - all types of motor (but especially permanent magnet types) can be built as a pancake.
- GM's Spark uses a slow high-torque motor and a single-stage reduction gear system (with a ratio of less than 4:1); this is not a new or unique idea.
Since the ring-and-pinion (in a traditional longitudinal drivetrain) are a right-angle drive (or "90 degree gearing"), this doesn't eliminate the right-angle drive. In a transverse design (like a typical front-wheel-drive car) there is no right-angle drive, but a pancake motor with a single reduction doesn't work because the large diameter of the motor case blocks one side of the output from the differential... although it could work in a two-motor setup (separate left and right motors, no differential).
If I understand the post correctly, the packaging would place a pancake motor with a vertical shaft, driving an existing final drive unit mounted rotated 90 degree about the lateral axis so the input (pinion shaft) is vertical. This would be an interesting idea for a DIY conversion, but lubrication of the gears might be problematic. For a production vehicle, the common and more efficient configuration is a transverse motor with a planetary reduction gear on the motor axis, and output through the hollow shaft of the motor.
The idea of putting the motor in the interior of the vehicle doesn't seem like an advantage to me. Yes, putting the controller inside seems like a way to protect it, but I think in practice all of this hardware belongs outside of the passenger compartment - especially if liquid-cooled - just like it is in production vehicles.
If anyone chooses a high-torque low-speed motor for a DIY conversion and drives the pinion of a longitudinal final drive directly, I suggest tilting the motor/pinion shaft up just enough to get sufficient ground clearance under the motor... for packaging, and to minimize lubrication issues.