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.
Gears also alter the direction of rotation. In the above example gear wheel A is rotating clock wise but as it turns, gear wheel B is moved anti-clockwise.
The drive gear (A) is known as the input gear.
The gear that is being turned (B) is referred to as the output gear.
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


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.

10 teeth
30 teeth
10 teeth
30 teeth
Output gear
Input gear
Stepping down has the advantage of producing more power although at a slower rate. This is often a big advantage with Automata as some of the mechanism can get stiff or are under tension and it makes turning the handle easier.
Stepping up produces a much faster output speed, but mechanically delivers less power. Be aware of this as you may find that your Automata doesn’t work properly or the handle is very hard to turn. However it is useful if you want something to move more quickly in relation to other things or just to go very fast.
This Automata has gear ratio of 3:1. So for every 1 turn of the handle the drive shrft turns1/3 of a revolution
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