Rookie Gearing Question

So my little 3rd graders geared their bot with 12 tooth driven gears and 60 tooth driving gear and two 24 tooth idle gears. The motors are in the center. However each side is turning in opposite directions so the bot can’t drive. Is there a way to reverse one of the motors? I don’t know enough about this to help them out.


Assuming that you guys are using driver control, this problem is easily fixed. Turn on the brain, go to drive control, then instead of going to run go down one to configure. From here, you can click the check button while selecting each motor to reverse individual motors or reverse the entire drivetrain. If you’re still having trouble, just reply to me again and I’ll try to help.


still not working. here is a pic of what they have done.20201014_130315


I don’t think this is a physical problem. This advice is what I would do:

Separately, I would strongly suggest massively gearing down your drivetrain as the wheels will go really fast with almost no torque. From the picture, it looks like your robot will not have enough torque to even drive really with the size of wheels that you are using and the friction in the drivetrain.

Good luck and let us know if you are having problems.


Are the wheels spinning at all? Or is the robot not moving on the field?
If it’s the latter, get the gear ratio waaayy down from 25:1 to somethingg more like 2:1.


Thanks for the picture!

They are going 60:12 or 1:5 (every time the big 60 gear turns once, the little gear turns 5 times. The 24 tooth gear isn’t an idler gear, it’s on the same shaft. So it’s a 24:12 or 1:2. So you really have a 1:10 drive. At full speed (100 RPM) the wheels will turn 1000 times. So it’s going to be pretty fast as @Noah10851B points out.

The post @ReMiSyS made is how to fix the motor issue. Did you follow it? Can you send a screen shot of the motor screen? Can you also tell us what ports you are using?

Ohhh, I think I understand now. So you mean each side is turning in opposite directions as in each wheel on each side is turning in opposite directions, like the wheel in the top left and top right go forward while the back two go backwards? If so, this is because of the amount of gears you have in place. If you have an even number of gears connecting the two wheels then that means that the two wheels will move in opposite directions. To fix this, you would need to add or take away one gear. I would recommend taking away one because as other people have pointed out this would be very fast with little power.


Also, I can’t tell from this angle but at the top of the picture is there another gear that the big gear is connected to? If it isn’t and the wheel is attached to the big gear then it would also move at a different speed I think.

Reverse the motors in the code. Just put the motors in and make sure you set one of them to reverse.

This has detailed instructions for reversing motors in vexcode.

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