Gears

Gears are comparable to continuously applied levers; as one tooth is engaging, another is disengaging. The amount of teeth on each gear wheel affects the action on the gear wheel it engages or meshes with. The gear wheel being turned is called the input gear and the one it drives is called the output gear. Gears with unequal numbers of teeth alter the speed between the input and output. This is referred to as the gear ratio.

Gears also alter the direction of rotation. In the above example gear wheel A is rotating clockwise, but as it turns, gear wheel B is moved anti-clockwise.

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Stepping down has the advantage of producing more power although at a slower rate.

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This Stepping up produces a much faster output speed, but mechanically delivers less power

CALCULATING RATIOS

If the input gear (A) has 10 teeth and the output gear (B) 30 teeth, then the ratio is termed 3 to 1 and is written down as 3:1
Simply divide the amount of teeth from the output by the input gear to work out the ratio. In the above example, for every complete revolution of the input gear the output turns 1/3 of the way round. In other words it takes three turns of A to rotate B once. This means you are slowing down the action and is referred to in engineering terms as Stepping Down. If B were the input gear and A the output gear, then the opposite happens and we Step Up. Then with one turn of the input gear the output gear would turn three revolutions, giving a ratio of 1:3.

parallel gears work in a similar way to the In line ones but are much easier to construct. The larger one uses popsicle sticks instead of dowel and is referred to as a Paddle gear.

Designing

When designing and making gear wheels you need to apply a little common sense. For example, the load or pressure put on the gears in automata are usually very small compared to that of a car gear box. This allows you to get away with things that you couldnŐt in other machines. However, you still have to follow some simple engineering guidelines. You will need to identify what you want to get from the gears. Try running through this simple check list;

1. Do you want the gears to step up or step down? (speed up or slow down the performance).
   
   
2. Do you want the gears to run parallel, or at an angle of 90o to change the direction of the drive?
   
   
3. What size do you need to make them? (small space means making smaller gears and this can get tricky).
   
   
4. What is the best or easiest material to make them with? (this may well depend on how heavy a load you want them to drive).
   
   

Here is a Gear template generator (You must have an internet connection)