3. Gear efficiency

General

Consider the gear shown in figure 39 . Let's assume that the pinion is the driving element and the wheel the driven element.

The work supplied to the pinion for 1 second is the "supplied or driving power" P _m . The power available on the wheel shaft is the "available or resistive power" P _r .

If we had P _r = P _m , the yield η would be equal to 1.

We can never have this condition, if only as a result of the relative friction of the conjugate gears, hence, P _r ...