Leather pinions must be protected from rats, which eat them freely.
This done he extends his enormous pinions 2 and sails majestically along, seldom deigning to flap his wings, the breeze doing the work for him.
The toothed wheels give a slightly better efficiency, but the worm gear is somewhat smoother in its action and entirely silent; the noise of gearing can, however, be considerably reduced by careful machining of the teeth, as is now always done, and also by the use of pinions made of rawhide leather or other non-resonant material.
When quick-running metal pinions are used they are arranged to run in closed oil-baths.
On such lines the beginning of a rack section is provided with a piece of rack mounted on springs, so that the pinions of the engine engage smoothly with the teeth.
