7 ms·

is there some type of clutch that allows the rear wheels to free-spin at higher speeds?

stetrain 6y ago
On Tesla cars both motors are physically connected to the gearbox/axles with no clutch. They are doing careful tuning of the motor inverter controls to minimize energy use from motors that aren't under active load. Tesla refers to this as "Torque Sleep" I imagine the process is basically tuning for the inverter output that minimizes power consumed as well as drag on the axle when the motor is not supplying active torque, or at least supplying less active torque than the other axle.
- mrfusion 6y ago
  Offtopic but you seem to know a lot. I’ve been wondering do Tesla’s just have one regenerative braking force when you let off the gas? Doesn’t this leave a lot on the table? Wouldn’t you get more energy by having say gentle braking regen and harder braking regen?
  - deleted 6y ago
    [deleted]
  - stetrain 6y ago
    You have analog control over the regen braking with the accelerator pedal. Push down to accelerate, lift up a little to maintain current speed, lift up a little more to start slowing down, lift off all the way for maximum regen. It takes a week or two to unlearn the habit of "popping" your foot off the accelerator anytime you want to coast without necessarily slowing down, but after that it basically feels like your right foot is directly connected to the speedometer in both directions.
    - brianwawok 6y ago
      If you judge distances well you can still pop your foot. The deceleration curve is optimized to be smooth (minimize jerk?).
      - chemmail 6y ago
        After a week you can judge pretty well. I use my brake pedal maybe once a week nowdays unless i'm driving alone and wanna feel some Gs.
        mrfusion 6y ago
        Is it hard to switch back and forth between a normal car after that?
        WorldMaker 6y ago
        Hard? No. Irritating? Not surprisingly. I've had ICE loaners when my car is in for repair, and missing "one pedal driving" happens a lot, but it doesn't stop me from operating the ICE vehicle. Perhaps weirdly the thing I think it makes the hardest is possibly videogames, which exaggerate controls in their own ways. I've gotten very frustrated with braking in most difficulty settings in the Forza series after driving an EV with "one pedal driving" capability for years now.
        brianwawok 6y ago
        Brakes are easy compared to keys. I keep getting out of ICE cars and just leave them running. Whoa, you need to tell a car you got out? Why?
    - bigiain 6y ago
      I own two very different motorcycles, a Ducati Monster900 (a 900cc twin four stroke) and a Cagiva Mito (a 125cc single cylinder 2 stroke). The Mito, you can let go of the throttle, have it snap back to zero, and you barely slow down at all no matter what gear it's in. There's practically no engine braking at all. If you want to slow down you have to grab the brakes. The Monster, in lower gears, will skid the back wheel if you chop the throttle from 75+% of peak rpm. You can pretty much get that bike down to walking pace in a fairly short distance without touching the brakes at all. (Thats a game I sometimes play on it, see if I can get home from work without touching the brakes, just slowing down using the throttle and gears.)
piva00 6y ago
Don't know about the Teslas but the Porsche Taycan does exactly that but for energy saving.
saberdancer 6y ago
Haldex type of 4 wheel drive do this, but in that case the rear wheels are disconnected at most times, they are engaged only when the car feels the need (hard acceleration, etc). It's not a big deal. In EV cars it is more complicated as they usually have an engine per wheel so you'd need a clutch at each wheel.

On Tesla cars both motors are physically connected to the gearbox/axles with no clutch. They are doing careful tuning of the motor inverter controls to minimize energy use from motors that aren't under active load. Tesla refers to this as "Torque Sleep" I imagine the process is basically tuning for the inverter output that minimizes power consumed as well as drag on the axle when the motor is not supplying active torque, or at least supplying less active torque than the other axle.

mrfusion 6y ago
Offtopic but you seem to know a lot. I’ve been wondering do Tesla’s just have one regenerative braking force when you let off the gas? Doesn’t this leave a lot on the table? Wouldn’t you get more energy by having say gentle braking regen and harder braking regen?
- deleted 6y ago
  [deleted]
- stetrain 6y ago
  You have analog control over the regen braking with the accelerator pedal. Push down to accelerate, lift up a little to maintain current speed, lift up a little more to start slowing down, lift off all the way for maximum regen. It takes a week or two to unlearn the habit of "popping" your foot off the accelerator anytime you want to coast without necessarily slowing down, but after that it basically feels like your right foot is directly connected to the speedometer in both directions.
  - brianwawok 6y ago
    If you judge distances well you can still pop your foot. The deceleration curve is optimized to be smooth (minimize jerk?).
    - chemmail 6y ago
      After a week you can judge pretty well. I use my brake pedal maybe once a week nowdays unless i'm driving alone and wanna feel some Gs.
      - mrfusion 6y ago
        Is it hard to switch back and forth between a normal car after that?
        WorldMaker 6y ago
        Hard? No. Irritating? Not surprisingly. I've had ICE loaners when my car is in for repair, and missing "one pedal driving" happens a lot, but it doesn't stop me from operating the ICE vehicle. Perhaps weirdly the thing I think it makes the hardest is possibly videogames, which exaggerate controls in their own ways. I've gotten very frustrated with braking in most difficulty settings in the Forza series after driving an EV with "one pedal driving" capability for years now.
        brianwawok 6y ago
        Brakes are easy compared to keys. I keep getting out of ICE cars and just leave them running. Whoa, you need to tell a car you got out? Why?
  - bigiain 6y ago
    I own two very different motorcycles, a Ducati Monster900 (a 900cc twin four stroke) and a Cagiva Mito (a 125cc single cylinder 2 stroke). The Mito, you can let go of the throttle, have it snap back to zero, and you barely slow down at all no matter what gear it's in. There's practically no engine braking at all. If you want to slow down you have to grab the brakes. The Monster, in lower gears, will skid the back wheel if you chop the throttle from 75+% of peak rpm. You can pretty much get that bike down to walking pace in a fairly short distance without touching the brakes at all. (Thats a game I sometimes play on it, see if I can get home from work without touching the brakes, just slowing down using the throttle and gears.)

piva00 6y ago

Don't know about the Teslas but the Porsche Taycan does exactly that but for energy saving.

saberdancer 6y ago

Haldex type of 4 wheel drive do this, but in that case the rear wheels are disconnected at most times, they are engaged only when the car feels the need (hard acceleration, etc). It's not a big deal. In EV cars it is more complicated as they usually have an engine per wheel so you'd need a clutch at each wheel.