You are required to respond to the design brief provided to produce a design proposal for an experimental rig which will measure the mass properties of a bicycle wheel, specifically:
- The mass of the bicycle wheel
- The polar moment of inertia about its rotational axis (See the design brief)
Design Brief - Overview
The mass and polar moment of inertia of a bicycle wheel is particularly important for cyclists who participate in competitive events. In general, it is desirable that both the mass of the wheel, and its polar moment of inertia should be as low as possible.
When comparing bicycle wheels, it is usual for the mass of front and rear wheel's to be quoted by manufacturers and reviewers, but it is rare that the moment of inertia is given. However, it is possible for wheels with the same mass, to have a different polar moment of inertia as a result of the fact that mass is distributed differently. This means that consumers often do not have all of the information that they would like regarding the difference between wheel sets.
In this design project, you are tasked to design a testing rig which would enable the experimental determination of the following properties of a bicycle wheel:
- The mass of a bicycle wheel [kg].
- The polar moment of inertia of a bicycle wheel about its rotational (rolling) axis [kg.m2 ].
Design Brief - Specific Requirements
The system which you design should perform tests, collect data and generate results with as little manual intervention as possible. The test should be designed to be repeatable.
The test rig should be able to be used with any standard 700c bicycle wheel. The hub widths will be 110mm at the front, and 135mm at the rear.
A high performance 700c wheelset might have mass properties as follows. These values are supplied only to give an indication of the approximate values which you might end up measuring. In reality many wheels could be 50-60% heavier, while a few could be a little lighter. You can use these values as the basis for any analysis of your design.
- Front Wheel
- Rear Wheel
o Mass = 0.55 [kg] = 550 [g]
o Moment of Inertia = 0.035 [kg.m2] = 3.5 [g.cm2]
o Mass = 0.75 [kg] = 750 [g]
o Moment of Inertia = 0.037 [kg.m2] = 3.7 [g.cm2]