Design considerations for gear systems

Gears are used when speed reduction is necessary i.e it helps in reducing speed.It is found in various automobiles,paint plants,cranes,escavators e.t.c. For a gear designer to design a good gear systems,he must have the following data at his fingertips:
.The power to be transmitted
.The speed of the driving gear
.The speed of the driven gear
.The centre distance
.The gear tooth should have wear characteristics
.The lubrication of the gears must be satisfactory.
.The gear teeth should have sufficient strength so that they will not fail under static loading or dynamic loading during normal running conditions.