Gears are very versatile and can help produce a range of movements that can be used to control the speed of action.

In basic terms, gears are comparable to continuously applied levers, as one tooth is engaging, another is disengaging. The amount of teeth each gear wheel has affects the action on the gear wheel it engages or meshes with. The gear wheel being turned is called the input gear and the the one it drives is called the output gear.

Gears with unequal numbers of teeth alter the speed between the input and out put. This is referred to as the Gear Ratio.

The following example shows how the ratios are calculated.

**If the input gear
(A) has 10 teeth and the output gear (B) 30 teeth, then the ratio is termed
3 to 1and is written down as 3:1
Ratio = number of teeth on the output gear B (30)
number
of teeth on the input gear A (10)
= 3 and is written down as 3:1**

1

**The first figure (3)
refers to how many turns the input gear (1) must turn in oerder to rotate
the out put gear 1 full revolution.**

**Simply divide the
amount of teeth from the input by the output gear to work out the ratio.
The principle behind gears is also very simple. In the above example, for
every complete revolution of the input gear the out put turns 1/3 of the way
round. This means you are slowing down the action and is referred to in engineering
terms as “Stepping Down”. If we reverse everything then the opposite
happens and we “Step Up”. Know it takes 1 turn of the input gear
to turn the output gear 3 revolutions and the ratio is now 1:3.**

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