Steel Spur

I often hear many people complaining about the rate at which they strip spur gears. As a solution they want to replace the plastic spur gear with a steel one. This is a bad idea for a couple of reasons.

The first reason would be a decrease in speed. A steel spur will weigh more than a plastic one. This translates to a higher rotating mass, which will take more effort from the motor to turn. This will result is a loss in torque and speed, and while it may not be dramatic it's something to consider.

The second reason is much more important. The weakest link in the transmission will fail when it is overstressed. Although it can happen, it is very rare for a differential or transmission gear to fail first. This is due to physics and the properties of gears in motion. In reality, the plastic spur will strip first 95% of the time. It is much easier to replace a stripped spur than to take the transmission or differential apart and replace a gear.

If you are having a problem with a large number of stripped spur gears, you need to examine how you are setting up your drivetrain. The first thing to check is your Pinion/Spur Gap. This is the most common cause for a stripped spur gear. Make sure the screws holding the motor are tightened down good and that they cannot move or slide. Over time the transmission housing can become worn, which can result in the motor moving. For more information on that, see my section on the motor mount. Make sure the screws holding the motor are tightened down good and that they cannot move or slide. Another thing to examine would the Slipper Clutch, as a nearly tightened slipper clutch can also result in a stripped spur gear. Also a little common sense helps as well. Don't land from a jump at full throttle as this can easily strip a spur gear. Following the suggestions above should cut down on the amount of stripped spur gears you have. However, from time to time they may still occur. Moving the slipper pegs from one spur to another can be a pain. To make changing spurs easier, I'd recommend removing the slipper pegs and using the steel ball method mentioned here instead.