I recently took a call from one of the members of the Kent Inventor's Club, which generally meets on the first Wednesday of each month on the Chatham Campus at Greenwich University, as to whether we had any good ideas as to how best to achieve a 50 to 100:1 gearing up in a single stage. The target application is wind turbines. The blades turn slowly but the generators need to turn fast. Conventional wind turbine gearboxes are vulnerable to lightning strikes going through them, and changing torques and large inertias also cause problems. Even when the gearboxes are carefully monitored, as they usually are on big machines, observers of wind farms may notice that the blades on such machines are often not turning when they should be. Inspired by the lighting generator I used to have on my bicycle wheel as a student, I suggested a friction drive, using the sort of lubricant employed in the Torotrak variable speed transmission. This can transmit lots of shear force while preventing the running surfaces from damaging each other when they slip. If anyone has a better idea, or a working device, please let them, and/or us, know.
Gearing up
I have in the past written about a number of clever ways of achieving very large gear reductions in a single stage, but what about going the other way?
