QuietDom -> RE: St. Catherine's wheel (11/27/2006 8:30:44 AM)
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Your biggest challenge is going to be the axle, as the entire weight of wheel plus sub is going to be borne on this pivot point, and it still needs to be able to turn easily. You'd be best to look for components originally intended for large industrial or agricultural machinery. Challenge #2 regards how this axle attaches. There will be a whole lot of shear force applied at that point. The classic image of the St. C's wheel has it secured to a wall. If you have a nice concrete wall (reinforced, all the better), and a half dozen Tapcon anchors (Big blue hex-headed screws) you should be fine. If you have drywall, you're out of luck, unless you can find an effective way to distribute the load across multiple studs. I can't think of one that doesn't involve tearing an 8' wide hole in your wall. I've seen one wheel positioned on a portable base, made of either channel-iron or square stock (I don't remember which.) That wheel was constructed on an angle, so that more of the axle and base were positioned directly under the load. I suspect it was far more comfortable for the subject than a truly vertical wheel, as well, since more of the subject's weight would be applied downwards onto the entire contact area, rather than strictly onto the restraints. As for the wheel itself??? Build a big X out of 2x4, as though you were making a St. Andrew's cross. Cut a big circle out of thick plywood. Nail the circle onto the cross. Attach screw-eyes, hitch rings, cleats and/or straps to taste. Add foot-supports, hand-holds, or what-have-you as you see fit. Finish, paint, or upholster. Try to position any point that will take a lot of stress on or near-to the underlying X-frame. That's the easy bit.
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