Section $15\mathrm{.}11$

SS $15\mathrm{.}6$ Design a pair of standard spur gears for transmitting $60$ hp from a $5200-$rpm motor to a $1300-$rpm machine. A safety factor of $1\mathrm{.}2$ should be used, together with $99\%$ reliability and a life of ${10}^7$ pinion revolutions at full load $($with the remaining lower$-$load cycles being negligible$).$ It is important to minimize size and weight. Use case$-$hardened alloy steel gears of $660$ Bhn $($pinion$)$ and $600$ Bhn $($gear$),$ and use Table $15\mathrm{.}5$ to estimate surface fatigue strength. Specify an appropriate combination of diametral pitch, numbers of teeth, center distance, face width, and level of manufacturing accuracy.