What is the equation involved woth scissor lifts, what is the force
needed to lift material at each height of the scissor. How long do the
legs need to be in order to lift a certain load to a certain height
depending on the angle of the scissor in realtion to the ground ?

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Clarification of Question by bigedmachine-ga on 12 Jan 2006 09:23 PST

Hi,

Thanks very much for your help. Yes, I am talking about the single
stage scissor lift with equal length arms. If you could give me the
equation for the force required to to accelerate a load at a given
speed that would also be helpful, as I guess I need to overcome
gravity as well as intertia of the load.

Thanks,
Ed

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Clarification of Question by bigedmachine-ga on 12 Jan 2006 21:23 PST

It's a manufacturing engineer trying to be a mechanical engineer.....I
suck at math and was trying to make sure I was on the correct track. I
also figured out inertia, which is nothing.
Thanks for the comment.
Ed

If you're talking about a lift that has straight, equal-length arms,
i.e. the distance from the horizontal-jack-screw attachment (or
horizontal hydraulic-ram attachment) point to the scissors-joint is
the same as the distance from that scissors-joint to the top load
platform attachment, then the equation is this:

       W + (W_arms/2)
F  =  ---------------
         tan(theta)

Where F is the force provided by the jack-screw or hydraulic ram, W is
the combined weights of the payload and load platform, W_arms is the
combined weight of the two scissors-arms themselves, and theta is the
angle between the scissors arms and the horizontal. If this is a
multi-scissors (series) lift, multiply the answer F above by the
number of stacked scissors mechanisms.

If the scissors arms are not equal-length, the equation must be
modified somewhat. Let me know if you want me to derive the modified
equation.

Hi,
Could you explain why only half the arm weight is used ?

Thanks,
Ed