Gear Math

Here you can see me and my gear box. I made it to see how much I could increase the power of my Lego 9v engine.


	First some Gear Math. This picture shows a row of gears laid flat on the ground. The speed of the gears at both ends will always be the same no matter what gears are in between them. So here the two red gears at both ends will always turn at the same speed (because they are the same size).


	This is different from gears lying flat. Here the gears at both ends can turn at very different speeds. When the giant yellow gear turns once the gear at the far right side will turn 405 times!

Now I will tell how you do the Gear Math. First you have to know the different sizes of the gears. I used one 40 tooth, four 24 tooth and five 8 tooth wheels. The relationship is: 5:3:1.

Now I will calculate the gearing using Gear Math! Each time the gear moves from one shaft to the next I calculate the gearing.

Starting at the far left side the 40 tooth wheel is connected to a 8 tooth wheel. So each time the 40 tooth wheel turns once the 8 tooth wheel turns 5 times. That’s because 8 goes into 40 five times. The rest of the gear wheels are geared by 3 times.

1 x 5 = 5 5 x 3 = 15 15 x 3 = 45 45 x 3 = 135 135 x 3 = 405

And with the engine mounted at 1:3 405 x 3 = 1215 Wow!

When I was finished with the construction (but before I put the engine on) I tried to turn the big yellow tooth wheel. It was hard to move. I could feel the shafts twisting.

When the engine turned the gear at the top I could feel the power from the yellow tooth wheel.

If you want speed you should put the engine on the yellow tooth wheel. If you want power you should put it at the tooth wheel at the top.


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