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Building a chair,need ideas

  1. May 16, 2008 #1
    Okay so completed a similar project the other day,but I am addicted now.

    I built a parallelogram binocular mount similar to this.

    Now I am trying to come up with ideas for a binocular chair....like this

    I would like to make the chair recline though. This is where I need help. I need to make it so goes up and down slowly (since in my design, the binos will be attached directly to the chair) , perhaps by use of a hand crank.

    I was thinking of using some kind of spiral jack or something...

    It needs to be cheap and the premise should be something along the lines of, I turn a crank and it raises or lowers a cylinder or something to that effect.

    Any ideas are appreciated and images of those ideas too if possible.

    I am also going to use a similar method to make the chair rotate about the vertical axis too.
    Last edited: May 16, 2008
  2. jcsd
  3. May 16, 2008 #2
    You will notice that most chairs do their reclining feature through the use of pulling a handle and allowing you to freely recline the chair while you hold that handle, and it relocks when you release it.

    So what you do is you use a hinge, and you attach a ridged circle at the end, and then you attach another ridged circle that locks with the hinge, and connect it to a handle that has a pivot just before the second ridged circle, and a spring to keep it in place until moved. Then pivoting the handle will allow you to recline.

    NOTE: I'll draw you a diagram and attach it in a few minutes.
  4. May 16, 2008 #3
    Though the simplicity of the idea is attractive, the motion needs to be very slow and controlled. The motions cuased by this kind of mechanism, I believe, would be too jagged.

    Thanks though!
  5. May 16, 2008 #4
    Actually, it would not be jagged at all, as in pulling the handle, it would release the two ridged circles, and if you add a small amount of friction between the chair and the area that reclines, the movement will actually be very smooth.

    (The drawing is terrible btw, so interpret the best you can)

    Attached Files:

    Last edited: May 16, 2008
  6. May 16, 2008 #5
    You can buy one of those reclining chairs (or get a broken chair from somewhere) .. remove the base (those wheels) and just hammer it into your system
  7. May 16, 2008 #6
    Is that something that PF does automatically....or did you really just link me to a definition of friction?:rofl:
  8. May 16, 2008 #7
    Any ideas on the hand crank mechanism?
  9. May 16, 2008 #8
    No. PF did that automatically.
  10. May 16, 2008 #9


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    I'm a really lazy bastard, so I'd go electric. There's nothing like good old scrap-yard power seat packs for strong, fluid movement. Of course, you need a 12VDC power supply, but that's never been a problem for me.
  11. May 16, 2008 #10
    I had this idea too, I think. You mean getting pulling a motor out of a car seat? What do these look like after you remove one from the actual seat? Is it easy to convert for my purpose?
  12. May 16, 2008 #11


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    I don't know whether or not they're all the same. The jaw-drive mechanism for my 'Alien' Hallowe'en costume was the 6-way pack from a '65 Mustang. It's essentially 3 motors in one case, with cable drives off of both ends of all 3 rotors. For my purposes, I removed 2 of the rotors, which still left it weighing at least a kilo. (That left me truckin' around with about 15 kg of steel on my head, but I had it suspended on springs from a welding helmet harness, so it was painless. :biggrin:)
    The pack itself was about 50% larger than a package of Smokies. (Maybe twice as big as a pack of wieners.)
  13. May 16, 2008 #12
    The pack itself was about 50% larger than a package of Smokies. (Maybe twice as big as a pack of wieners.)

    these above mentioned measurements are standards from National Bureau of standard weights and measures. (Danger, your my hero)

    instead of getting the electric motors from a car seat, why not use the whole car seat? everthing is already there, just need power. pretty comfortable too
  14. May 16, 2008 #13


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    That's pretty much the way that I was thinking, although not all functions are necessary for the purpose. One advantage is that you can snipe the control buttons from the driver's door panel while on site. That can save a couple of bucks down the road.
  15. May 16, 2008 #14
    Needs to be portable. I think I have ruled out the seat pack.

    I am thinking of using some sort of combination of springs and dampeners....like a screen door or something....

    I open to more suggestions...
  16. May 17, 2008 #15


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    If you want super simple, how about a car jack, i.e. screw jack, directly attached to the back of the chair? If you wanted, you could increase complexity by putting a right angled drive in the back, then run one end up to the back of the chair and then the other out the front between the legs of the person sitting in the chair. Then you could even look into providing a drive to attach a cordless drill to power it.

  17. May 17, 2008 #16


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    Good idea, Fred. A screwjack is probably my favourite actuator mechanism for just about any purpose that doesn't require high speed. Awesome torque and controllability, and just about bullet-proof.
  18. May 17, 2008 #17
    I like this idea...hopefully I can find a decent jack at the scrapyard for short money.

  19. May 17, 2008 #18
    I found one online. It goes from min height of 6.4" to max height of 13.5"

    I am wondering if this what the best range of inclination I can get out of this will be.

    Taking the horizontal as a reference axis and sitting upright to be 90 degrees.
    Sitting at 90 and laying at 0 degrees are unnecessary.

    Hmmm. Time to get out some paper here to see what the compromise will be.
  20. May 17, 2008 #19


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    No need to compromise, pal. You can always add secondary leverage or gearing to your primary unit to obtain the results that you want.
  21. May 17, 2008 #20
    Could you elaborate on what you mean? I know there is a way around this....

    I am thinking something like this[​IMG]

    Where the circle is a hinge and where the length of the overhanging portion d is part of the back rest (all one piece). By changing the length of d and having the actuator act at the end of d i can vary the range of the angle of inclination.

    I think this is a simple but effective idea. I like simple...less can go wrong....supposedly.

    (remember when images actually showed up in threads? not just links to them....what gives?)
    Last edited: May 17, 2008
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