# How do gears and gear systems and idle gears work?

Hello everyone!
Recently, my team has been modifying our AMOGO based robot to a 6 motor drive train, and the gear systems in the chassis just confuse me.
Now, I don’t want to find a solution to the actual robot, as our coach said he had something in mind, but I want to understand how they work.
Can anyone help?

If the top gear is the driver, spinning CW, then the second gear down will spin CCW, and the bottom gear CW again.

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Could you be more specific, and perhaps post pictures?

I understand that you’re trying to get me to understand the directions, but the thing is, I don’t understand the gear ratio aspect of gear systems.

Gear ratios refer to the ratio of teeth on one gear connected to another gear. They can be geared for speed (larger driving gear on a smaller driven gear) or geared for torque(smaller driving gear on a larger driven gear)

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Let’s say you have two gears, one with 100 teeth, and the other with 50. We know that every time the big gear moves one tooth, the small one moves one tooth. This means that when the big gear does one rotation, 100 teeth get moved. This would move the small gear two revolutions.

We know that energy must be conserved, so when more energy goes into making it spin faster, it will have less torque to keep total energy the same. This means that gears can change their speed at the expense of torque, and vice versa.

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Wow, that makes a lot more sense to me now! Thanks a lot!

But what if the gear link was more than just a driven and driver gear? What if it had 3, 4, or even 5 gears in the same system?

Gears between the driven and driving gears are known as idler gears. I’m not as clear on how idler gears affect the gear system, but I’m sure someone else can explain the finer details of it

Idler gears have no effect on gear ratio. The only purposes they serve in a gear system would be 1) changing direction of the driven gear, 2) connecting previously independent systems, or 3) covering distance between driving and driven gears. When calculating gear ratios, idler gears are ignored completely; just focus on the driving and driven gears.

On the other hand, if you wish to incorporate a more aggressive gear ratio than is possible with a single gear to gear system, you would have to utilize a compound gear train, where the next stage in your gear reduction begins on the same axel as the driven gear.

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You can essentially just link all the systems together to figure out effect. Idler gears as mentioned previously, don’t have an effect.

Ex: 100 tooth gear, 50 tooth idler gear, and 100 tooth gear.

For every time the first 100 tooth gear revolves, the 50 tooth gear will revolve twice. So you have a 1:2 ratio, 2x.

Every revolution of the 50 tooth gear will rotate the second 100 tooth gear halfway around. So you have a 2:1 ratio, 1/2x.

If you combine those together, you get a 2x ratio and a 1/2x ratio, which cancel each other so that the final speed is 1:1.

2nd Ex: 150 tooth gear, 50 tooth idler gear, and 100 tooth gear.

For every time the first 150 tooth gear revolves, the 50 tooth gear will revolve thrice, three times. So you have a 1:3 ratio, 3x.

Every revolution of the 50 tooth gear will rotate the second 100 tooth gear halfway around. So you have a 2:1 ratio, 1/2x.

If you combine those together, you have a 3x ratio and a 1/2x ratio, which create a ratio of 3/2, final speed is 3:2.

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