[Ken Patton]

Kenneth-

The CIM motors and the gearboxes are pretty consistently good quality, and the problem you are describing sounds fairly big, so I would suggest that you consider two possibilities:

1. There is some serious friction caused by parts sliding together somewhere in the driveline.

or

2. The PWM signal from the controller is not the same to each of your speed controllers.

If its number 2, you should be able to check what your program is doing to see if there is some calculation error, and you should be able to see quickly if the speed controllers are going "full throttle" by looking at the red and green lights that signal full-back and full-forward.

If it is number one (my guess is that it is), you should look for parts that are rubbing against each other. Usually they tend to make noise, and heat up if you run them at high speed. Look at every interface in the driveline - is there a washer rubbing up against a bearing, is there a gear thats rubbing against something? Look to see if the gearbox was assembled correctly - lots of teams use it so it should be pretty straightforward for you to make yours right. Put the bot up on blocks, turn the wheels with your hands, feel for odd resistance against turning. Pull a motor out - if everything is running on ball bearings (and now no motor to resist you turning the wheel) the driveline should run super-free. If you feel drag or hear crunchy sounding noises you are probably getting close to the problem. Be a detective - you'll find it. I've seen experienced robo-nuts take a loong time to figure out where the problem is, so don't give up easily.

This might be a problem that you only see under load (like when the robot is pushing against something, or when you turn and the wheels scrub sideways). If this is the case you need to look for deflections in your chassis - are they causing shafts to come out of alignment? If so, FIX IT, make your chassis stiffer, you'll be glad you did. Are the wheels sliding sideways and rubbing up against something?

If you post your findings (try to be clear and concise, and explain your methods) you'll see that people will be willing to help you solve it through this forum.

Hope this helps,
Ken