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Lift anyone

  1. Mar 18, 2008 #1
    Lift anyone!!!

    Hii Everybody,

    I am involved in a project and I need some guidance for my design.

    Design Purpose:

    I am trying to create/find a mechanism that will provide me with up-down motion. For example think of a match-box type rectangular box that needs to be moved up-down in y-direction. It probably needs to move up-down about 1 ft and I need a mechanism that can life 100 lbs weight.

    Things I have thought of:
    scissors-lift
    some spring loaded mechanism
    motor for up-down motion with gears

    My problem:
    I am not sure how to go about evaluating different mechanisms. Do you know any websites or resource that could help me with it? Or any suggestions or ideas as to how should i approach the problem and what mechanism you think is the best?


    Thanks for the read. Appreciate your time and efforts:)
     
  2. jcsd
  3. Mar 18, 2008 #2

    stewartcs

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    Pulley systems are easy to use and make. The mechanical advantage they produce are of great benefit.

    Google "pulleys" and I'm sure you'll find tons of information (pun intended). :smile:

    http://en.wikipedia.org/wiki/Pulley

    http://library.thinkquest.org/27948/pulley.html

    http://www.howstuffworks.com/pulley.htm

    CS
     
  4. Mar 18, 2008 #3
    wow that was quick but let me explain it a bit more. Please see attached word document for a rough schematic.

    I can not have my mechanism visible so it has to stay beneath the box. Hopefully the picture clears things up a bit.

    Btw, thanks for the quick reply.
     

    Attached Files:

  5. Mar 18, 2008 #4

    turbo

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    How about a cog-belt-driven mechanism that actuates threaded cogs at the corners of the box. The cogs would climb 4 threaded rods, and you could design the mechanism such that the thread pitch of the rods matched the mechanical abilities of the drive (fine threads would require less force, but would take more time to raise the box for a given motor RPM).
     
  6. Mar 18, 2008 #5

    Danger

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    Welcome to PF, Brian.
    I agree with Turbo about the use of lead-screws; they're just about my favourite approach to any heavy lifting problem. I'm not sure about the need for four of them, though. In my experience, one driving unit with some stabilizing guide rods can usually do the job. Your initial thought of a scissors-jack seems pretty good to me, though. You have all of the stabilization of a multiple guide rod setup, without the hassle of anchoring sufficiently strong rods. It maintains the screw-jack advantage of irreversibility (ie: no power required to maintain position.)
    Your picture is a bit vague. Is the elevator to come up through a hidden opening in the counter? (I ask because this looks suspiciously like a design for a stage illusion.)
     
  7. Mar 19, 2008 #6

    stewartcs

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    As soon as any device lifts the box it will be visible. Do you mean that it has to be non-visible prior to lifting? For example, if you put a hydraulic cylinder under the box, as soon as the box was lifted the cylinder rod would be exposed.

    CS
     
  8. Mar 19, 2008 #7
    Thanks Everybody for the quick and enthusiastic responses.

    I am reattaching the word file to give you the top view as well along with the front view. When I said that mechanisms can't be visible what I meant was that whatever mechanism I use needs to be attached to the bottom surface of the box that I am trying to raise.

    Sorry for my sloppy drawing. In the front view, the mechanism will lie hidden behind a cardboard/foamboard for now. So no worries there. Also the box's top surface, in its stationary position will be 3" below the counter surface and I want to lift the box until the bottom surface of the box gets aligned with the counter surface.

    I hope I am not confusing you all. Thanks. I look forward to more suggestions.
     

    Attached Files:

  9. Mar 19, 2008 #8

    Danger

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    The added information just confirms it for me. I really think that the scissor-jack is the best approach.
     
  10. Mar 19, 2008 #9
    Really, Everyone thinks scissors-lift mechanism the best idea?

    If yes, do you know of any good vendors that sell them and ship them fairly quickly?

    100 lbs max weight lifting requirements.

    Also, I am not sure what sort of motor would I need to drive my scissors-lift mechanism.
    any suggestions on that?

    One more thing,
    do you know any way I can lift the box without electricity but still keeping it simple enough that a kid could raise it up and bring it down without a lot of effort?
     
  11. Mar 19, 2008 #10

    Danger

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    Yes, I honestly believe that it's the best way to do it; I can't speak for anyone else.
    You can probably get one for free or very cheap. Just hit a scrap yard and pull one out of the trunk of just about any Japanese car you run across. Weld or bolt a steel plate the size of your box footprint to the top, and you're set.
    Any motor/gearbox combo that can approximate the strength of an average human is sufficient. You said that you want it to be reversible, so I'd go with a DC unit that you can run from a converter or battery. My wheelchair motors that I bought as salvage would be more than adequate, but they normally cost a few hundred dollars each. A really big determining factor is how fast you want this thing to go up and down. A power-seat motor pack from a car would be good if it doesn't have to zip along. They're compact and have pretty decent torque. A windshield wiper motor with the attached transmission would probably work as well, but I'm not really sure about it.
    As for the 'without electricity' bit, the basic answer is 'Idunno' in regard to the scissor-jack setup. I don't know enough about the kid to determine whether or not it could hand-crank the jack with 100 lbs. on it. I suspect that it might be reasonable; a slight-of-build woman can lift the ass-end of a Toyota with one.
    You could also use a pneumatic or hydraulic motor with a simple valve, but that wouldn't make sense; if you have a pressure supply for either one of those, then you can just use an actuator cylinder instead of the screw mechanism.
    I think that I need a bit more input as to exactly what you're trying to accomplish. You can't just introduce new little sub-factors like kids in the middle of a design session.
     
    Last edited: Mar 19, 2008
  12. Mar 20, 2008 #11
    Haha thanks Danger.

    I'll explain my project in a bit more detail. I am trying to create a Pop-up drawer in the kitchen island. Drawer(which I have described as the box) pops up from the middle of kitchen island and is supposed to go 3" below island's top surface when not in use. So I am looking at electric and manual options as well.
     
  13. Mar 20, 2008 #12

    Danger

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    Okay, that clarifies it nicely. Since it's a permanent installation, I retract my motor suggestions. A reversible 110 VAC unit would be better—maybe a 1/2" electric drill or garage door opener.
    I'm curious as to why it has to sink 3" below the surface. Is that clearance for a cover? If so, you could just make the lid of the box out of counter-top material and have it settle flush in the 'down' position.
     
  14. Mar 22, 2008 #13
    actually i didn't clarify it well enough. It is going into the island but it cant be permanent installation. I am building a portable/moveable island so I don't think scissors lift will work.
    I need to mount my mechanism on the wood panel and It would have to be light weight.

    It has to sink 3" below the surface because we are planning to use the space between 3" and counter top surface for varieties of things mainly displays of work or a game.
     
  15. Mar 23, 2008 #14

    Danger

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    In that case, I must think upon it some more. Since I am severely inebriated at the moment, that's going to have to wait until tomorrow.
     
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