How does a auto lift works?

[casper_838]

Hi everyone,

I have been doing some research on how does a car/auto lift work (2 post), but have no luck with it. Just wondering if any of you can help me out here. All the web site have installation manual but they don't tell you exactly how does it work. Thanks

[ales]

I'm assuming you mean the lifts that are used in workshops to lift cars? Most use a screw principle - the two posts have screw-like shafts running inside them, and those are rotated by the motor(s). The horisontal elements (the ones that the car rests on) have the holes with threads that the shafts go through, and as the shafts rotate, the screw principle makes the car go up or down, depending o the direction of rotation. Usually the lidts have one electric motor on top of one post, and the two shafts are linked somehow to each other (chain running through the floor) to ensure that they both rotate at the same speed and the car is raised evenly.

[curtis73]

Some operate hydraulically. The ones with the big post in the middle are hydraulic and require a separate hydraulic source. Many of the twin post side lifts use hydraulic as well with an electric motor driving the pump.

[casper_838]

Thanks guys...yes, i am looking at the one that are 9000 lbs two post lift and it uses an electric motor and two hydraulic cylinder with one in each post. I just wonder would you know any books or website that would have all the informations how it operate from let say when you load the car to the lift to the car off the ground to desire height. When I goes into a shop, I notice they only press one switch and it lifts up the car. So what's operating when you press the switch? Thanks again for your input!

[RandomTask]

Some use hampsters to power a magnet and lift the car...

[curtis73]

Pressing the button turns on the motor which creates hydraulic pressure. To let the car down, you push that lever which opens a valve releasing the pressure. Its no different than your floor jack. You use the lever on the jack to pump fluid into the ram and the lift uses an electric motor and pump. You screw out a valve to release the pressure on the jack to lower it, and on the lift you push a lever which opens the release valve.

The lift should also have safety latches. They are the clunk, clunk, clunk you hear when the lift goes up. Its just a racheting tooth that holds the lift up in case of hydraulic failure. In order to lower the car you have to pull a release lever to disengage the tooth.

[MagicRat]

Originally Posted by curtis73

Some operate hydraulically. The ones with the big post in the middle are hydraulic and require a separate hydraulic source. Many of the twin post side lifts use hydraulic as well with an electric motor driving the pump.

All of these ones with the big center posts use compressed air.........so they can use that same shop air compressor that is used to run the hand held air tools.
This is why the center post is so big, since there is only 100 psi of compressed air available, the surface area for the cylinder must be large to get enough lifting forces.
Hydraulic lifts use much smaller cylinders with much higher pressures.