not a smooth claw rotator, help

Hello everyone,

Just wondering about my claw rotator i designed. I used it for my arm/claw. It didn’t go smooth, infact it didn’t even go okay. The arm goes incredibly fast and with a few turns bangs on the ground and on the panel of my modified squarebot. Is this a problem including motors? Is the motor that comes with the starter too fast of a motor, do i need a slower one? If i can work with this motor, I’d appreciate ideas. And even more than ideas, pictures. They’d help me understand better, thanks guys.


You have a couple of options,

  1. Gear down the motor to slow down the speed of the arm.
  2. Set the motor at a lower percentage power output using the remote control. (check the manual)
  3. Include limit switches or bumper switches that warn you when to stop the claw. This would prevent the claw from hitting the robot base.

There are no other motors than the one that they currently sell. In my opinion #2 should do the trick. Consider doing #1 if you are able to gear it.

Also consider switching the motor to a servo which would help you to better control the arms range of motion.


yes if the arm only needs to rotate 120 degrees then a servo is way better

but the problem is if you use a 1:2 gear ratio then its only 60 degrees, 1:3 only 40 degrees and so on

so using a servo is kind of not an option because im guessing you must be using some gear train

Yes you need to gear that down, gears are very useful if you look here

I used gearing on this robot, i used the 84 tooth gear and a 12 tooth gear with 1 motor and it slowed the arm down a lot to the point where it took 2 or 3 seconds to fully go backwards.

This is the cause of your problem and i suggest using the 84 tooths gear but if you don’t have that just use the 60 tooth gear it should be fine.

Hello and thank you all for your helpful replies,

The problem is, Robofreak, that i have used the 60 tooth gear for the claw rotator. What do you mean by, “gearing the motor down?” Do you mean just to stick alot of drive shafts throught the holes of the gears and to my claw rotator? Please clarify. Thanks. :smiley:

P.S. Everyone scorin’ good? Who’s going to state competition for science olympiad?

Bascally gearing it down means to use a smaller gear to drive a bigger gear.

In your case you would want a 12 tooth gear driving a 60 tooth gear.

What this means is that you connect the 12 tooth gear to the motor which will spin a 60 tooth gear. This increases the total torque 5 times and reduces speed by 5 times. It also goes the opposite way if you had the 60 tooth gear driving the 12 tooth gear the speed would increase 5 times and the torque would be reduced by 5 times.

Its really simple when you think about it.

If you still need help i can make a small module to show how to make this.

Also if you need more motors look at my servo modding post, it is easy to do and all you need is a vex motor gear replacement which they include 3 sets in the starter kit so i know you have them.

Yeah, i see what you mean. The teeth would slow down the process if a smaller wheel was to drive a wheel with more teeth. I understand how it would reduce the speed 5x.

Use MATH!! 60/12 = 5.

Anyway robofreak, thanks for all of your help. I don’t need a small module to understand the concept. You put it quite simply. Ahh, by next competition i’ll do better, a lot better.:slight_smile: