We designed a label for printing out on self-adhesive film. We did a 6-up layout on an 8.5" by 11" sheet size. These are used to cover the valve access openings, and may be peeled off to get at the valves. |
Making "Aerodisc" Wheels Using The Spandex Trick: We resolved that the Moon Rover Trikes project would be made as inexpensively as possible. Using wheels from our pile of 20" wheels was part of this economy plan. Unfortunately, we didn't have two matched sets of three for the trikes. We had painted rims and chrome ones. So, we decided to use the mixed wheels, and cover them with stretched spandex membranes. Materials cost for these wheels was about $10 per wheel. These are also good for use on chipped, scraped or rusted wheels. |
We started the process by making two fixtures for holding the wheels from plywood scrap. One fixture, shown here, centered the rim by blocking against the inside of the rim. The other, for doing the second side, blocked the outer edge of the rim for centering. 1/4" plywood rings were made using two different diameter holesaws. This gave a smooth flat surface at the hub area where the spokes mount.An 18" square of spandex fabric was then stretched tightly over the wheel and stapled to the underside of the fixture. The inner diameter of the hole corresponds to the bearing race. |
After stretching the skin over the wheel, re-stapling as needed, we then wrapped a length of baling wire around the outside, tightened it and twisted it. This forces the spandex to wrap around the rim edge. The inflated tire presses this against the inside of the rim, ensuring that it stays in place. We then used a soldering iron to melt a small hole in the center for an axle to go through. As seen in the first photo above, we took a wrench socket wrapped in plastic tape, of the right size to force the spandex down into the opening in the wooden washer, after saturation. This is held in place by an axle which goes through the hub and a hole in the fixture base,. and a pair of nuts.We then saturated the spandex with epoxy resin, being careful to also saturate the area which wraps under the rim. |
After the initial saturation cured overnight, we used 100-grit dry sandpaper to knock off any surface bumps. We then applied a second coat of resin and allowed it to cure. This coat fills in the fabric texture of the spandex. On the inside surface, in the valve area, we placed a disc-shaped piece of fiberglass cloth, as reinforcement. A 2.5" opening is later cut inside the reinforced area, for acess to the valve.The was saturated with epoxy and cured before stretching the other side of the wheel. Both sides are given a second coat and then wet-sanded with 220-grit, and it was given its first primer coat. As needed, we used spot putty to fill any remaining small surface flaws. Succeeding coats of primer were added, as needed. When the primed surface seemed to be perfect, we wet-sanded it with 400-grit, and applied a coat of Krylon flat white. Yellow is not very opaque, so it's best to have a white undercoat. |
We designed a label for printing out on self-adhesive film. We did a 6-up layout on an 8.5" by 11" sheet size. These are used to cover the valve access openings, and may be peeled off to get at the valves. |
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