Gearboxes
Gearbox Efficiency
Gearbox efficiency η (eta) describes the ratio of useful output power to input drive power. It is a key measure of mechanical efficiency and determines how much of the energy input is available as usable motion at the output.
Definition and Calculation
| Gearbox Type | Efficiency η | Note |
|---|---|---|
| Planetary Gearbox | 95–98% | Very high efficiency |
| Bevel Gearbox | 95–97% | High efficiency |
| Spur Gearbox | 96–99% | Highest efficiency |
| Worm Gearbox | 50–90% | Strongly dependent on lead angle |
Practical Relevance
Efficiency directly affects motor sizing: a gearbox with η = 0.80 requires 25% more drive power than one with η = 1.00 for the same output power. This is especially important for worm gearboxes with low efficiency (high reduction ratios, small lead angles), where the drive and cooling system must be dimensioned accordingly. At the same time, low efficiency in worm gearboxes enables self-locking — an advantage in holding applications without a brake.