Spur gears are the most typical kind of gears. They have straight teeth, and so are mounted on parallel shafts. Occasionally, many spur gears are used simultaneously to create very large gear reductions.
Spur gears are found in many gadgets that you could see Liquid-ring Vacuum Pumps around HowStuffWorks, like the electric powered screwdriver, dancing monster, oscillating sprinkler, windup noisy alarms, washing machine and clothes dryer. But you won’t find many in your car.
This is since the spur gear could be really loud. Each time a gear tooth engages a tooth on the other gear, one’s teeth collide, which impact makes a noise. It also increases the pressure on the gear teeth.
To lessen the noise and stress in the gears, most of the gears in your car are helical.