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Thread: help needed with scissor lift

  1. #1
    Associate Engineer
    Join Date
    Jun 2013
    Posts
    1

    help needed with scissor lift

    Hi, I've been trying for some time to construct a scissor lift capable of lift a wheelchair and user to a height of 50cm to enable use of a caravan. I found a web page related to this site which has a formula for calulating force required. It doesn't seem to be correct! The total weight including Platform will be less than 120kgs and the starting angle of the arms is just under 20 which according the the calulator should require 330 kgs force. That wasn't enough to move the lift so I increased the available force to a stage where I now have 600kgs or 6000N acting on the lift and it barely moves. The construction has one arm fixed at the top and all others are free moving, with two 3000N actuators pulling the two lower arms together to raise the Platform (I'll worry about fixing it in place once I can get it lifting). It works ok with about half the working load on it. Should I.... A/ Increase the starting height thereby increasing the arms starting angle , which will make things easier to move. B/ Increase available force C/ Move the actuator to a position where one end is fixed D/ Go back to using a tent. Thanks for all and any advice.

  2. #2
    Technical Fellow
    Join Date
    Feb 2011
    Posts
    1,043
    Hi, welcome, but I am a little confused. "one arm fixed and all others free moving," sounds like the problem to me.

    Can you supply a sketch or some clear pics of the system as it is highly unlikely that the Calculator here is incorrect.

    Also, "I'll worry about fixing it in place," is a comment for concern.

  3. #3
    Lead Engineer Cake of Doom's Avatar
    Join Date
    Aug 2012
    Location
    UK
    Posts
    434
    Think about the design for a moment. You have some free moving (because you haven't secured them) actuators and a shallow start angle. I highly doubt it's the numbers on the calculator that are incorrect.

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