Exceed RC Buggy Engineering Analysis
engine flywheel and the screw holding it in place, and the spur gear must be between the width of the transmission frame and the height of the transmission frame.
Contents |
Diagram
Figure 1: The diagram showing the two gears interacting in the problem
Assumptions
- Gears spin on bearing with negligible friction
- Friction between gears is negligible for these calculations
- No slipping of gears
- To calculate inertia, treat each gear as a solid disk
- Number of teeth does not affect transfer rate
Governing Equations
Discussion
The main restricting factor on the size of the gears is the space allotted. However, there are several factors which will make this calculation more difficult than simply maximizing one gear size and minimizing the other. To start with, the minimum radius on the smaller gear will likely be too small as there will be no way to get the amount of teeth required for the gears to properly mesh in such a small radius. Second, and most important, is that by increasing the size of the transmission gear to its maximum value, the resisting mass moment of inertia also comes into play. The largest possible gear is not necessarily the most efficient. It must be limited it so that the rotational inertia of the larger gear will not cause the entire system to slow down beneath a point where it would be at its maximum. The calculations may show that for these small gears this rotational inertia will not make a large difference, but they may show that the gear needs to have a diameter a centimeter below the maximum size it could be simply based on size.
The other part of this car which has a rotational energy transfer due to gears is the gear box. For this part, a similar calculation would have to be carried out except that in this case there are three gears and thus a larger mass moment of inertia counteracting the torque which is applied. By choosing the most efficiently sized gears which fit within the limits given, the RC car will become more efficient and provide more power and speed to the wheels.
