ABSTRACT
The design and operation of gears is more complicated than almost any of the common mechanical devices. Gear operation involves both rolling and sliding contact. There are dictionaries of gear terms and much of the terminology is truly specialized. Looking back in history, the first “gears” were wooden devices where the spokes off two hubs meshed with each other to transmit power and synchronize the equipment. One of the weaknesses of spur gears is that the power pulses are discrete, i.e., as each pair of teeth mesh a power pulse is delivered, and they are relatively noisy and rough. The damage could be the result of misalignment but more serious is that it could indicate there have actually been reversing loads and tremendous stresses on the teeth. One of the difficulties in assessing through hardened tooth wear occurs on start-up when the teeth begin pitting and it is initially difficult to tell the difference between corrective and destructive pitting.
