College of Engineering Unit:
The manufacture of bicycles requires stringent testing to ensure their quality and safety. To test a bicycle frame, a multitude of testing machines are needed, which can present a high cost to a small scale manufacturer. This is the problem that our sponsor Scott Campbell of Celilo cycles tasked the team with solving. The standards for the tests are outlined in ISO standards (from 2015). The team decided to narrow the scope of the project down to the pedal force test. This test requires that a downward force (of 1200 newtons) be applied to the pedals within a frequency range of 1-3 hz. To accomplish this, a cam and lever system was used. A motor rotates the camshaft through a set of pulleys in order to increase the motor's mechanical advantage. The cam lobes are 180 degrees out of phase with each other. A beam rests on each cam lobe. Close to the pivot of the beam, a steel cable that is attached to each pedal, connects to the beam. When the beam is lowered, the slack in the steel cable is taken up, and all the weight from the beam is applied to the pedal. This is the operating principle of the testing machine. This design was chosen out of the many concepts the team came up with for a number of reasons. This solution allowed for the reuse of many of the sponsor's materials from previous capstone projects (this project has been ongoing for multiple teams/years). In the spirit of keeping costs low, the team primarily used wood that the sponsor already had. By using a combination of hand calculations and software it was determined that the team could also reuse a motor the sponsor already had, (with some speed reduction required). Lastly a sensor to measure the force was added between the pedal and beam. This sensor allied for confirmation of the forces being applied to the frame.
Industry Sponsor(s):
| Attachment | Size |
|---|---|
 Bike Test Machine Poster | 1.01 MB |