A two post lift has two hydraulic cylinders. One per post. When you push the "up" button a motor starts and runs a hydraulic pump which shoves oil into the post cylinders which have a flat chain arrangement that raises the lifting arms - and if it is in the arms correctly - your car. There is a lever which bleeds the cylinder back to the oil tank and allows the arms to go down.
If a hose or seal failed while the car was up and you were under it - the car would fall rapidly and squash you like a bug.
Two safety ratchets engage as the lift is going upwards - making a prounounced clunk with each engagement. If pressure is lost to the cylinder - the ratchets will stop the lifting arms from dropping.
If one ratchet fails - there is a system of steel cables on pulleys that make the lifting arms lift and drop in unison - so it will stay up on one ratchet.
That's the last clue without drawimg a picture.
If a hose or seal failed while the car was up and you were under it - the car would fall rapidly and squash you like a bug.
Two safety ratchets engage as the lift is going upwards - making a prounounced clunk with each engagement. If pressure is lost to the cylinder - the ratchets will stop the lifting arms from dropping.
If one ratchet fails - there is a system of steel cables on pulleys that make the lifting arms lift and drop in unison - so it will stay up on one ratchet.
That's the last clue without drawimg a picture.
