How much torque would an electric motor have to have to lift an average car/operate an electronic car jack ?
A motor does not lift a car directly, but through a system. What you need is power from that motor, and the higher the power the faster the system can do the lifting.
Speed of Response - Hydraulic fluid responds faster because it's near incompressible. Force Available - Is dependent on pressure applied. Hydraulics are safer because if the system is breached energy is immediately dissipated with decrease of volume. Pneumatic pressure requires balancing volume before energy is stabilized. That's why both systems are Hydrostaticly tested. Supply of Operating Fluid - Hydraulics requires a reservoir with pressure supplied by a pump. Pneumatics require accumulators to store energy because it takes to long to build energy in a compressible fluid. (Yes in physics and dynamic energy, air as any gas, is considered a fluid.) Weight of the System - The higher the pressure the lower the component weight. High Pressure Pneumatics are dangerous. As to the medium, oil is heavier than air.
The Hydraulic System is used in some aircraft to raise and lower the landing gear, deploy flaps, and larger aircraft the flight controls are powered using hydraulics. The pneumatic system is used to inflate door seals, inflate de-ice boots, and power some instruments. They are not interchangable systems. The hydraulic system is used because there is a 1 to 1 ratio of displacement. With pneumatics, an air cylinder displacement could move only a portion of the desired movement and raise the pressure.
If the mechanical advantage(gear ratio) is high enough you could lifyt a car with 1 fly power crawling on a tread mill, But; it would take all year to do it.
Depends on weight of car, how much of it you want to lift, how high, and what gearing or lever action you are connected to for motor size and torque capacity. Worm or screw drive to scissors jack would require several dozen foot-pounds.
