Possible to warp/bend screw in two post car lift?

October 18, 2015 2:49 PM

This is what I'm talking about, but MUCH older. It uses a motor to belt drive a 10ft vertical screw, which in turn chain drives another screw on the other side. A ~2600lb car was left on a lift like this , raised to the top for the better part of a year. Can this damage the lift-screw?

The car was in the air at the top of the range of the lift throughout an engine rebuild, transmission swap and full front end suspension upgrade. Recently, as the project was finally coming to a close, we were able to lower the car without issue, but upon lifting the car again, the lift seemed to be experiencing a heavy load, and the result melted the centrifugal contacts on the motor which activate at higher speed to switch to a lower voltage circuit. We got the smoke out of the wires.

Can a prolonged lift like that bend the vertical screw-posts just enough to cause undue resistance?

posted by shenkerism to Technology (5 answers total)

If it went down ok I'd wonder instead about whether, after a year, there's just no lubrication/there's corrosion/ the grease is gone on whatever bearings there are on the big screws. The weight of the car helped it overcome that on the way down; on the way up, too much friction. Something to consider.
posted by BillMcMurdo at 3:27 PM on October 18, 2015 [1 favorite]

It shouldn't. The safety factor in a lift is huge which leaves a lot of extra material to keep things right.

I'd suspect the switch sticking closed because your overloads should pop before an overload causes the switch to fry. Easy enough to test though once you get it working by throwing a meter on and seeing what the draw is.
posted by Mitheral at 3:48 PM on October 18, 2015

Can a prolonged lift like that bend the vertical screw-posts just enough to cause undue resistance?

Nope. The lift was likely about to fail through poor maintenance and your car happened to be on it at the time. Something failed in the lift and the time the TR8 was on it was irrelevant.
posted by Brockles at 7:28 PM on October 18, 2015

Is the lift down now? Then leave it down, and get someone who knows about machinery to inspect the screws and the mechanism. Do not put another car up there until it has been cleared as fully functional. The electrical issues are a symptom of the problem, not the cause of it. It is most likely to be wear, leading to excessive friction, on the threads, usually due to lack of lubrication over an extended period.

I have experienced one of these lifts seizing, fortunately it was 'only' about one-third of the way up: getting the car off the lift was the sort of fun you only want to read about. That lift went straight to the scrap metal people, and was replaced with a hydraulic one.
posted by GeeEmm at 7:31 PM on October 18, 2015

Best answer: The amount of time the car was left on the lift is a non-issue. It's engineered to support that load, and a static load won't deform the screw. A sudden dynamic load might, but that's really unlikely with this mechanism. Like said previously, it's a matter of maintenance/corrosion/electrical malfunction etc.
posted by werkzeuger at 7:27 AM on October 19, 2015