4 ms·

I just don't see the point, and I say this as someone who loves manuals in ICE engines. Control over the transmission allows me to adjust the torque curve to m

• Animats 2y ago
  > A direct drive electric motor has no torque curve, so a transmission is pointless. Actually it does, but it's much flatter than that of an ICE. For a brushed DC motor, it's a straight line, from max torque at stall to zero torque at no-load full speed. The original Tesla roadster had a 2-speed transmission, because the motor didn't have a high enough operating speed range. That worked badly. The jerk at shifting was high, and the transmission wore out. Tesla finally developed a water-cooled motor with more speed range, got rid of the 2-speed, and retrofitted their first cars.[1] Variable speed electric motors with smooth acceleration are an artifact of smart control. The motor itself is not that well behaved. DC electric traction motors used to have "transition controllers", where the windings were switched from series to parallel. That's what the "throttle notches" on electric locomotives did. Here's a locomotive which works that way, a common Diesel-electric locomotive in India.. This loco is an old Diesel-electric, where the Diesel runs at a governed constant speed and driving is done on the electric side.[2] This is the true electric equivalent of a manual transmission. The big white handle on the left is the transition controller, and the two levers in front of the driver control engine and train brakes. This setup is workable for slow-accelerating trains. Watch the driver work the white handle like a shifter. This takes some training and practice. If you move that lever too fast or incorrectly, fuses will blow or the train will stall. That really is a manual control. Streetcars, which spend much of their time accelerating or decelerating, had an good electrical "automatic transmission" by the 1930s.[3] That's a large electromechanical device which uses transition switches and resistors to smoothly control acceleration. The driver just has an accelerator pedal, and all that machinery manages the motor torque. That's the power train of a PCC car, the base model San Francisco still uses on Market Street. The controller has speed and pedal position as inputs, so, like an automatic transmission, it's following what the power train is doing. Stomping on the pedal will give you normal full acceleration, and will not hurt the machinery. So this really is an automatic. Modern electric cars with AC motors have a similar function, created with electronic controls. Older golf carts demonstrate how electric drive lurches without some smarts in the controller. So that's what the electric motor equivalent of a "shifter" really does. (I'm really bored this week. Hence these long posts. I'm waiting for a open source project to fix something they broke in a new release, and my main project is stalled on that. They're in denial at the moment.) [1] https://www.autoblog.com/news/breaking-tesla-has-a-solution-for-their-transmission-woes-get https://www.autoblog.com/news/breaking-tesla-has-a-solution-... [2] https://www.youtube.com/watch?v=hRWMaykHDzg https://www.youtube.com/watch?v=hRWMaykHDzg [3] https://www.youtube.com/watch?v=CqnsNhDVefs https://www.youtube.com/watch?v=CqnsNhDVefs
  • devmor 2y ago
    Wow, that was really interesting information that I didn’t know! Thank you for the enlightenment.