Gears, Gears and More Gears

What is a gear?

A gear is a wheel with teeth that mesh together with other gears.

Gears change the• speed• torque (rot. force)• direction of rotating axles.

Different types of gears

Spur gears

Belts & PulleysBevel gears

Idler gears Worm gears

Gear Motion

If this were my “Driver

Gear,” it would be

causing the motion

Thus the “Driven Gear”

would be compelled to move

Where Do You Find a

Simple Gear Train?

Two meshed gears

will rotate in

opposite directions.

Watch gears

11. Found in:

– Watch

– Sewing Machine

– Motor

Where Do You Find a

Simple Gear Train with

Idler?

Two meshed gears will rotate

in opposite directions.

An Idler Gear allows the

drive and driven gears to

rotate in the same direction.

8. Found in - Paper Transport Rollers

Gears

Generally, the Gear Ratio is

calculated by counting the teeth of

the two gears, and applying the

following formula:

Gear ratio = Number of teeth on driven gear

Number of teeth on driver (drive) gear

Gear Ratio

Gear Ratio….continued

Driver (Input) Driver (Input)

Driven (Output)

Driven (Output)

GearsGear Ratio - Calculation

A 100 tooth gear drives a

25 tooth gear. Calculate the

gear ratio for the meshing

teeth.

Gear ratio = Number of teeth on driven gear

Number of teeth on driver gear

Gear ratio = driven 25 = 1

driver 100 4

This is written as 1:4Or .25

Important

Calculations

Work Done = Force x Distance moved in the direction of the

force

Power = Total Time Taken

Total Work Done

Efficiency % =Power Output

Power Input

Friction: - Resists the movement of one surface over another

X 100

Efficiency = Mechanical advantage

Velocity ratio

Gears Gear Speed :- Calculation

A motor gear has 28

teeth and revolves at 100

rev/min. The driven gear

has 10 teeth. What is its

rotational speed?

Speed of driven gear = Number of teeth on driver gear x 100

Number of teeth on driven gear

Speed of driven gear = driver = 28 x 100 = 280 rev/min

driven 10

28 teeth,

driver

10 teeth,

driven