Note on Scissor Lift Equations

One of the 1508 Vex teams is working on a scissor lift for Gateway. I was helping them with the equations and ran across some bad info on the net at Engineers Edge which is a popular search hit. Here is my note to them and also what I think are the correct equations.

There is also a good mathematical derivation by Spackman in the links.

I updated my post to show the torque required on a scissor pivot to actuate the lift.

τ = (W + wf/2)Lcos(phi)

Again, if there are N stages then the total torque = N*τ

W = load weight
wf = frame weight of a single stage
L = half length of a scissor leg
phi = the interior leg angle with respect to the floor.