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theremino
Keymaster

These days we are planning for Rover (carts with wheels or tracks) and I found myself having to frequently measure the Backlash of the engine output pin.

Il Backlash, or “Game” in Italian, It is due to gear backlash. In genus greater is the reduction ratio and there are more and more gears the game increases. And of course also it counts as these gears are made, if they return springs of the game, if they are planetary etc..

Here's an example of the engine that seems designed by a mad scientist. This engine because of all its wheels has a tremendous game, even 15 degrees.

To measure the game keeps the engine stopped, and rotates the output pin in one direction and the other with a reasonable force. manually rotating the pin feels a clear area and two stop decided on the one hand and on the other.

I'll have to measure different engine models and, since they use a protractor is awkward and inaccurate, I made a method that I will facilitate testing.

Perhaps this method can be useful to others for which the audience here.

Measure the backlash

1) Attach a toothpick from 58 mm to the output pin.

2) Move the output pin manually in two directions.

3) Measured by calliper movement of the tip of the toothpick.

4) The millimeters of displacement are approximately the degrees of backlash.

Measurement error

With this method are obtained at lower errors 1% until 30 degrees.

The errors are due to the fact that with the gauge will measure the rope and not the arc of a circle for which the increase of the length is measured more and more by default.

To partially compensate for this effect using a length of 58 mm instead of 57.3 calculated. (the value 57.3 You are obtained by 360 degrees divided 2 for pi-greek).

To measure accurately with engines that have low backlash (less than two or three degrees) should use a toothpick along 573 mm and divide by ten times the measured value.

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