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Originally Posted by Dick Linn
OK. Lacking a sketch, try this. Think of 3 sections of tubing, say 3", 2", 1 inch, or whatever nests relatively nicely. Between each of the two junctions, place either a length of surgical tubing or, outside the junction between successive section of tubing, place a coiled clock spring on the outside, business end pointed down. When you collapse the tubing, it will tend to want to spring out to it's former position because of the "springs" placed in the tubing. At the far (top) end, you attach a cable, which is routed straight down through the tube to a winch at the base. The only function of the spring or surgical tubing is to allow the relatively light cable and PVC pipe to extend to the desired height. Reversing the direction of the winch will pull the beastie up. If the PVC tubing is flimsy, so much the better, as it will not interfere with the upward lifting.
A variation of this is to put a small pulley at the top of the base tube on the outside, one on the bottom of the second tube and so forth. Sort of like a Sine wave propagating itself up and down throughout each successive layer of tubing. Retracting the cable will at first extend the tubing then, when at full extent, pick the whole thing up. Having very weak, flimsy tubing might help when lifting, as you only have to lift a foot or so. You won't have to worry about how (or if) the tubing nests back in again. PVC pipe is cheap! Change it if it breaks or bends.
A sketch would be a lot better than my explanation...email me at rlinn@wrsystems.com if you want something you can see. |
The springs and surgical tubing could work if the design conforms to the requirements laid out by FIRST for stored energy devices, as well as being safe.
I am not following you on the variant of that with the pulleys installed on the outside of the various sections of tubing. With a pulley installed on the outside bottom of the 2nd stage tubing, how will it slide and retract into the 1st (base) stage tubing.
My variant of that is to use a combination of what was mentioned in a previous thread here, and and your coiled spring suggestion. I'll send you a simple PDF file of the concept I have in mind.