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Technology: Engineering Our World
Just like the six simple machines, gears provide mechanical advantage.
This advantage is calculated as follows:
Mechanical Advantage (M.A.) =
Number of Teeth on Driven Gear
Number of Teeth on Driver Gear
The velocity, or speed, of the driven gear is calculated as follows:
Velocity of Driven Gear
Number of Teeth on Driver Gear
Number of Teeth on Driven Gear
= Number of Teeth on Driver Gear ×
An example of these gear calculations is shown in Figure 8-44.
Types of Gears
Gears are designed in a variety of types for a variety of purposes.
The five most common gear types are spur, helical, worm, bevel, and
rack-and-pinion.
The spur gear is the simplest and most fundamental gear design. Its
teeth are cut parallel to the center axis of the gear, as shown in Figure 8-45.
The strength of spur gears is no greater than the strength of an individual
tooth. Only one tooth is in mesh at any given time.
gure 8-41. When a small gear drives a
larger gear, the input torque is multiplied.
gure 8-42. A simple gear train.
gure 8-43. A compound gear
train. Two gears are attached to the
same shaft.