Moby Build Instructions / Wheel Spacing

Hi everyone,

We are a new team using this school year to practice before entering into competitions next year. We are starting by building from instructions (Clawbot, Moby, etc.). I have a question that I have not seen asked here:

Should there be ANY side to side play in any wheels or gears on an axle? My intuition says that all drivetrain wheels and all gears (specifically the ones used for the Moby arm lifts) should have sufficient spacers to keep them from sliding side to side.

However, the instructions seem to allow for some major side to side movement based on the spacer sizes they suggest. In the Moby instructions, for example, a 2" standoff is used to space where these components go but the wheel/gear + spacers + collars do not add up to anywhere near 2" from what I see. Any help is appreciated.



Welcome to the forum! You seem like a very diligent person, but even if you’re following instruction manuals, it’s important to make your own choices when it comes to the robot. If you feel that it will perform better in a way that deviates from the instructions, it’s preferable to take performance over precision. In general, too much side-to-side movement can cause the gears to skip, wear out inconsistently, or just be annoying. Personally, I’d keep measuring it and minimize the side-to-side (regardless of the instruction manual), but it’s really up to you.


Personally I would say that you should have little, but very minimal side to side movement. Having none will cause friction and will put stress on your motors, but have too much will make it imprecise and also not function very well. Personally I find exactly how many spacers i need to put on, and i ensure that one of those is a 1/8th inch spacer. I then replace the 1/8th inch spacer with 3 of the 1/32 teflon spacers. I do this because one 1/8th inch spacer is 4 of the 1/32 ones, and by taking out only 1/32 from the entire spacing it gives it just enough room to not cause friction and motor stress without making it imprecise or wobbly. Of course you should find what works best for you by running your own tests, this is just what I do.


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