Torque required to operate scissor jack

[Mlu333]

Hi, I would like to know if anyone knows of any calculations as to find the torque required to operate a scissor jack for lifting a vehicle. The purpose of this exercise would be to find the required torque for an electric motor that would be capable of doing the job.

 

[NormPeterson]

No math or numbers, but I've seen a cordless impact tool do exactly what you're asking about. Four times in succession.


Norm

 

[NickE]

for a mechanical engineer this should be pretty easy, a couple levers and a screw.

are you sure you're a mechanical engineer? this forum (Eng-Tips) is for working, real engineers.

Nick

 

[Mlu333]

It seems that my question has been misinterpreted I am looking for actual formulas that will help me determine the torque required to raise the jack (with the variables: vehicle weight 1000kg, pitch of screw thread 5mm). Norm thank you for pointing that out that could mean very low torque is required to do it.

B-Tech Mechanical Engineering
South Africa

 

[NickE]

I meant generating the equations should be relatively easy.

Nick

 

[JayMaechtlen]

The scissors jacks that I've used had really crappy screw threads.
That meant they would hold position, but initial calcs vs reality might surprise you.
Performing a test with a torque wrench could be illuminating.

Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[Tmoose]

Based on the ones I've seen supplied with vehicles and a few aftermarket ones from 1968 to 1995 the sophistication of the thrust bearing under the screw thread varies from nylon and steel washers to ball bearings. Makes sense "nice" jacks have better bearings sinceThreaded fastener theory is likely to say the torque to overcome the under head friction is likely to be very roughly on the order of 1/3 the torque applied to the fastener threads.