Quote:
Originally Posted by Halon
Electric motors can have full torque throughout their entire RPM range, so unlike a standard car that needs a gear box to keep them in the ideal range, an electric car (like a Tesla Model S) doesn't necessarily need them. So I too wonder why they're using gear changes. Maybe based on whatever gear reducer they're using, the motors just aren't rated at enough RPM. I'm sure it was all figured out by someone 100x smarter than me so there's a good reason I'm sure.
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Gearing multiplies your vehicle's wheel thrust. even at 400 LBS of engine TQ, if there was no force multiplication, the vehicle would be going nowhere fast.
Take a 2014 Tesla Model S 85. Its electric motor is rated at 443lbs of TQ. They then multiply that by a 9.73:1 drive gear, so suddenly the car is off the line at a more reasonable 4200 lbs of thrust (assuming a fairly standard 25" diameter wheel). With electric motors, typically they lose efficiency the faster you spin them.
I would suspect that formula E cars, the could be running gear ratios in the neighborhood of 20:1, which will eat up 16,000 of engine RPM in just a few KPH, and be required to gear down for more speed.