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Designing a car jack?

  1. Nov 6, 2007 #1
    Designing a car jack???

    I have been set a design project in which i am to design a car jack. i am really having trouble starting...so could anyone tell me which kind of car jack would be the best/easiest to deisgn (ie: scissor jack etc - but not a hydraulic one), and also what is the best way to start?

    many thanks! :cool:
  2. jcsd
  3. Nov 6, 2007 #2


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    If this is for a physics/mech eng class - you probably want to look at:

    How much weight do you have to lift?
    Hint - this isn't the mass of the car, the car is acting like a lever pivoting on the wheels on the other side.

    How much force can your user supply, and so what mechanical advantage do you need?

    How far do you have to lift it?
  4. Nov 6, 2007 #3


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    Welcome to PF, Charlie.
    Mgb covered the main questions, but there are a couple of ancilliary ones. Is this just a single-purpose unit (ie: one model of car and one user), or is it to be more universal? For instance, you'd need a variable 'starting' height for different tire sizes and types of suspension. Also, a very high mechanical advantage would be needed if someone in poor health would have to use it.
    Probably the easiest to design and build would be the old ratchet style bumper jack, but I strongly recommend against it. They don't offer a lot of advantage, and were never safe at the best of times.
    If you definitely don't want to use hydraulics, which is best, something based upon a lead-screw would be second choice. The scissors type that you mentioned is very good.
    Remember to design your top plate so that it can properly support the part of the car that you want to use as your lift point, be it a lower control arm or a frame rail or rear axle tube or whatever. There should be some sort of 'lips' on it so the load can't slip off even if it shifts a bit. Remember: Safety First.
    Good luck with it.
  5. Nov 6, 2007 #4
    two of the most simple ''jacks''
    are used in races, formula 1 uses a ''L'' shaped jack or a bent lever
    no moving parts and one man powered by his weight

    indy cars use onboard airjacks, plug in an compressed air line
    and up pops the car, the jack is two tubes with one end sealed ,
    the other end inside the other tube
  6. Dec 21, 2011 #5
    Re: Designing a car jack???

    I have the same problem. I need to design a jack that lifts 10,000N of force, with a force applied by hand of 180N (turning the jack handle ) .... and I need to lift it by a height of 0.275m
    where do I start ?
  7. Dec 21, 2011 #6
    Re: Designing a car jack???

    By following the suggestions listed above. Don't take it as rude, but you wont learn anything if we tell you how to do it...
  8. Dec 21, 2011 #7
    Re: Designing a car jack???

    You're right .. I have been working on it and I got stuck a bit at converting the turning moment of the screw... into the horizontal Force acting on the on the sides of the ''scissor jack'' which will then raise it.

    I worked out the turning moment of the thread while turning to be 2036N
    and set the thread pitch to 1cm but I don't know how to find the possible diameter of the thread if I do this, then im hoping that I should be able to find the horizontal force
  9. Dec 27, 2011 #8
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