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The description in an earlier thread (see beginning of any hit at
I think 6063 .75x.75x.06" tubing, at under $1/foot, is probably a dollar less per beam than arrow shafting, plus being easier to attach to the axle. In TW's plan, the beam is fixed to the axle, which rotates in bearings and turns the sensor pot that provides feedback to the PID controller. One way to save on bearings would be to glue the pot to the side of a .5" (.840" OD) PVC pipe in line with a drilled-through pivot hole, and use a fixed axle. Schedule 40 .5" PVC at .17#/ft is slightly lighter than the aluminum tubing, and .75" PVC at 0.226#/ft is slightly heavier. Both have about 0.11" wall thickness in Schedule 40 so are fairly stiff.
-jiw