Types of gearing: Various types of gearing are used on a motor vehicle. The gearboxes employ one or more of the following: Spur, teeth parallel to the axis, used on sliding mesh. Helical, teeth inclined to axis to form helix. Double helical, two sets of opposing helical teeth. Epicyclic or planetary, spur or helical gears rotating about centres that are not stationary. Gear ratio (single gear train): The gear ratio, or velocity ratio, between a pair of gear wheels is in inverse ratio to the number of teeth on each. Thus:                             NB/NA = DA/DB= nA/nB                           … Continue reading The Gearbox (Transmission)