Smoothies on the go!: Bike Tire to Axle Transmission

The current design of the transmission wheel is a strip of bike tire coiled into a circle and held together with a mixture of Epoxy and bike repair glue. However, the design is not very durable and uncoils frequently, requiring immediate repairs. Furthermore, the only glue strong enough to hold the wheel together is not readily available in Nicaragua. So, although the wheel worked well for short-term blending, if it is to be used daily for multiple hours at a time, we need to find a more secure solution sticking with the bike tire method.

SECURING THE END OF THE COIL

We had a very difficult time figuring out a way to secure the end of the coil, so that was the first place I chose to focus on when designing a glue-free design. Initially, we glued the inside of the tire so it behaved more like a single, flat piece of rubber rather than a tube, and found that we even needed duct tape to secure the end.

Somehow weaving the end of the tire back into the coil presented its self as the most promising solution. There were a few different ways to weave the tire. One possibility was to have multiple cuts and “basket weave” the outer layer of the tire. Another idea was to cut two slits in the tube, the top half at one location, and the bottom half at the other, and join the two. The last idea was a latch design, where the end of the rubber would have a single, secure weave that effectively latches into rubber it is on top of. The basket weave proved to be very difficult to construct even using duct tape, so it did not seem likely that it would be the most practical approach, and although it was easy to construct, the slit method was not very secure. The latch method proved to be both secure and simple to construct. After making a duct tape prototype, it was possible to address other problems with the wheel design.

PREVENTING UN-COILING

The layers of the original wheel that were not glued together slipped out of the coils, resulting in a dysfunctional wheel. All that was needed was a simple support system to keep the wheel structurally sound. The first idea tried was a piece of piano wire across the bottom of the wheel that was connected to the outermost rubber layer. However, having only one strip of wire on the bottom did not hold the wheel together properly. To add additional support, two more wires were added to the top of the wheel, on either side of the axle. At all locations, the piano wire was threaded through the outer layer of rubber and bent at the ends to keep the wire from coming loose.