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telescopic tubing

I'm in the early stages of designing a piece of furniture that has a single column suspened from the ceiling. It must adjust vertically carry ~100 #'s ecentrically and have as little play as possible and be inexpensive to make. I'm thinking of using 2.5" x 2.5" x .125" square tube female & 2" x 2" x .125" male. My local steel providers don't provide anything with closer tolerances how do i take up the slack. I remember seeing a piece of weight lifting equipment use a kind of teflon tape as a type of anti friction / shim. Any ideas would be appreciated.

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Reply to
Vittorio
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How do you plan to connect this to the ceiling? Do you mean hundreds of pounds of side forces?

Reply to
Ian Stirling

As you are finding out, the regular grades of square tubing are not very good at telescoping. The sizes don't match and the tube usually has an inside weld flash the size of mount Everest. Some tube manufacturers make a range of 'telescoping' tube. These are sized to give good fits, have the flash removed on the inside as well as the outside, and have matched corner radius. Not commonly stocked by the local suppliers but it is available. Plan on getting quite a bit of it at one time.

Your other choice is to weld .120 (or perhaps .104" for some extra clearance) pads on the outside of the small tube, inside of the large tube (one end of each tube). You can cut a grove to accomodate the flash. The assembly must be done from the end opposite the telescoping end. This might be a safety factor in your case or make it impossible to take apart.

I'd suggest using the pads for you prototype and early production. If you get to any volume, switch to the telescoping tube.

cheers.

Vittorio wrote:

Reply to
Roy Jenson

Teflon tape:

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Reply to
cej

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