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Gearbox Efficiency Test

This testbed demonstrates that you actually gain efficiency by using more gearboxes, despite the prevailing wisdom.

The two parallel powertrains are both set up to tune the engine throttle (with a PID) until the wheel is spinning at 10 RPS. The wheel has a brake set to 0.27 which provides substantial load. Once the PID reaches zero error, the power consumed by each wheel should be identical.

The red powertrain has 4 gearboxes.
The green powertrain has 53 gearboxes.

There is a small, non-constant RPS loss over gearboxes, which is usually intepreted as "loss", but this power is not actually lost. In order to perfectly test gearbox efficiency, I used 53 gearboxes and stepped the RPS back up to match the red powertrain. The two powertrains thus have almost the same gear ratio.

With both powertrains at the same ratio, the engine spins at the same RPS to produce the same wheel RPS, and therefore the same overall power. With the engine spinning at the same RPS, we remove any dependence on non-linear engine power/RPS.

The difference is that the green powertrain, with more gearboxes, requires LESS throttle to achieve the same power, and consumes LESS fuel.

In conclusion, torque calculations are weird. You gain extra torque over gearboxes which more than compensates for the RPS loss.

Just note that you need to step up your transmission if you use lots of gearboxes, because your gear ratio is dropping quite a lot more than advertised, even using 1:1 gearboxes.


You can see this for yourself by launching the test bed and waiting for the engines to settle.