This article describes the changes I made to Moon Buggy after the 2006 Baltimore Kinetic Sculpture race. The result was version 1.1 (the it-really-worked-this-time version), which I ran in the 2006 Columbia Festival of the Arts)
June 6, 2006
The first order of business, after recovering from the Race, was to fix the drivetrain. It fell apart waaay too many times during the race! The photo shows two items getting fixed.
The first charge was to improve the connection between the end of the bicycle frame bit (where the rear wheel would normally be) and the frame of the sculpture. Bicycle frames usually have slots to hold the axle of the rear bicycle wheel. The slots make it easy to install or remove the wheel, and they're oriented such that the weight of the rider and the tension in the bicycle chain tend to oppose each other, so the axle doesn't slide around in the slot once it's installed. Well, in my sculpture there was no intrinsic force opposing the tension in the chain, so when I pedaled hard the bicycle frame popped loose. I fixed it by cutting the slots off entirely and mounting the frame with a bolt and bushing through each side of the frame. (The bushing allows the joint to rotate when raising the seat for water travel.) In the photo one of the bushings is installed and barely visible (see the circled bit). You can also see the corresponding hole (no bushing installed yet) in the opposite plate on the bicycle frame.
The other improvement was to put the bicycle's idler into the gear train so I could stop pedaling while moving forwards without the chain popping off. In the photo, to the right of the circled part, I've installed a mounting plate on the right side of the bicycle's rear axle. I just drilled holes to match those in the flange that would normally hold the spokes of the wheel and used lots and lots of small bolts. (It would have been easier, and probably more secure, to weld the plate on, but I think it looks cooler this way.) The sprocket that will mount to that plate is sitting loose on the axle.
June 9, 2006
And here's the drivetrain all back together. I don't have any photos from the right angle to illustrate the attachment of the bicycle frame, unfortunately. This photos least shows how the new sprocket is connected to make use of the idler. I also had to redo the mounting of the dérailleur, since it was made to mount to the slot in the bicycle frame (which is now removed). You can see a bit of that detail in this photo as well.
The next items on the agenda were the problems the sculpture had in the water portion of the race: the paddles and tires falling off. I made new, larger paddles out of some of the leftover pink polystyrene foam. I expoxied a layer of fiberglass cloth over each and ran the cloth out a couple of inches onto the surface of the wheel for a nice strong bond. Those paddles will get smashed before they fall off! Though, of course, I hope neither of those happens...
To address the problem of the tires falling off, I ran some additional strips of closed-cell foam around each wheel. Each strip goes around the entire circumference of the wheel in a single piece with some extra bits stuck on where the ends meet to help hold them together. The strips mechanically hold the tires in place in the water, regardless of whether any of the glue holds.
I also painted the insides of the wheels after installing the new paddles. That looks much nicer now!
And here's the sculpture put back together, ready for another test drive around the neighborhood. It doesn't look much different, but this time it works!