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In an electric car? Really? I don't know too much about electric cars, but it's my impression that gears and transmissions are completely unnecessary in an elec

In an electric car? Really? I don't know too much about electric cars, but it's my impression that gears and transmissions are completely unnecessary in an electric car. Please correct me if I am wrong.

orra 2y ago
Precisely. Electric cars almost universally have one fixed gear, with the engine smoothly providing variable torque.
- jaredhallen 2y ago
  This is a nitpick for sure, but as I understand it, electric motors provide pretty much constant torque throughout their operating range, which is one of their benefits. It's the speed of the motor that varies, and consequently the power, which is a function of torque times speed.
  - ttshaw1 2y ago
    No, electric motors exert the most torque at zero RPM. That's where you can put the most current through the coil, because there's no back-EMF. It's why EVs are so zippy from a stop. The torque-speed curve is a straight line, with 0 torque at max RPM and a constant power.
    - ttshaw1 2y ago
      Sorry - not constant power, obviously, since at the extremes the power is 0.
    - floxy 2y ago
      For synchronous motors. Induction motors (like the auxiliary/dual motors used on something like the Chevy Equinox EV) have a different torque/speed characteristic. https://www.engineeringtoolbox.com/electrical-motors-torques-d_651.html https://www.engineeringtoolbox.com/electrical-motors-torques...
- ZeroGravitas 2y ago
  I believe multi-motor EVs sometimes tune the motors to different uses, switching between one or the other (or both) to provide a similar effect as a gear shift.
- serf 2y ago
  this is a cost savings feature that was enabled by electric motor torque at low speed and the consumer's willingness to sacrifice high speed operation to focus on city driving. electric motors hugely benefit from gearboxes, they're not used as a means to simplify and encheapen.
rightbyte 2y ago
There is usually a speed reduction from the motor towards the wheels. Direct drive or wheel hub motors are uncommon. The difference is that one fixed gear ratio is usually good enough. Heavier vehicles more or less need multiple gear ratios for EV drivetrains too.

orra 2y ago

Precisely. Electric cars almost universally have one fixed gear, with the engine smoothly providing variable torque.

jaredhallen 2y ago
This is a nitpick for sure, but as I understand it, electric motors provide pretty much constant torque throughout their operating range, which is one of their benefits. It's the speed of the motor that varies, and consequently the power, which is a function of torque times speed.
- ttshaw1 2y ago
  No, electric motors exert the most torque at zero RPM. That's where you can put the most current through the coil, because there's no back-EMF. It's why EVs are so zippy from a stop. The torque-speed curve is a straight line, with 0 torque at max RPM and a constant power.
  - ttshaw1 2y ago
    Sorry - not constant power, obviously, since at the extremes the power is 0.
  - floxy 2y ago
    For synchronous motors. Induction motors (like the auxiliary/dual motors used on something like the Chevy Equinox EV) have a different torque/speed characteristic. https://www.engineeringtoolbox.com/electrical-motors-torques-d_651.html https://www.engineeringtoolbox.com/electrical-motors-torques...
ZeroGravitas 2y ago
I believe multi-motor EVs sometimes tune the motors to different uses, switching between one or the other (or both) to provide a similar effect as a gear shift.
serf 2y ago
this is a cost savings feature that was enabled by electric motor torque at low speed and the consumer's willingness to sacrifice high speed operation to focus on city driving. electric motors hugely benefit from gearboxes, they're not used as a means to simplify and encheapen.

rightbyte 2y ago

There is usually a speed reduction from the motor towards the wheels. Direct drive or wheel hub motors are uncommon. The difference is that one fixed gear ratio is usually good enough. Heavier vehicles more or less need multiple gear ratios for EV drivetrains too.