Algodoo

Well using the motor slider values can be a decent bet, but the best way to do it is by scripting the motor.
Try putting this script into the motor's postStep:

(e)=>{
keys.isdown("right") ? {
motorSpeed = motorSpeed + 0.05
} : {
motorSpeed = 0.001
}
}

WARNING: The axel will just get faster and faster and FASTER.

Hope this helps!