Driving straight

[Creator Mat]

Our team this year decided to go with a 6 wheel drive dropped center drive train (out of date but still similar pic here) it is based off of team 221's universal chassis. We finally got it driving but found that is biased towards one side and cannot drive straight. We couldn't find anything wrong right away before we had to leave.

So long story short does anyone now of any common reasons for this type of drive train to be driving in circles?

We know it isn't a programming error (first place we checked) and plan to do a speed test and to check the alignment tomorrow to see if our frame is crooked. Any other suggestions? Other than driving in circles it runs fine.

[MrForbes]

How big are the circles? there are things like speed controller calibration, motor direction differences, etc that will make one side run a bit faster than the other.

[Vikesrock]

The most common I have seen is gearbox binding. I would look over very closely the gearbox(es) on the side that runs "slow". Try spinning each side by hand, do they feel the same?

Another common possibility is different length wiring runs to the two sides. Make sure your wiring path from the PDB->Jag->Motor is the same gauge and approximately the same length for each motor in the drivetrain.

[LLogan]

If it is only slightly veering, it may be because you're using old motors and motor-bias is getting to you. If that's the case, fiddle around with the encoders in your code for scaling that'll decrease/get rid of the problem.

Check if the two CIMs on both sides are powered. You might be powering just one on one side and two on the other.

Lastly.... check if one side's chain has too much tension. The tension might make it harder for everything to turn on one side.

We had this problem too. We propped it up on some blocks so the wheels were floating off the ground. Eventually we found out it was a programming error, but it's a lot easier to diagnose the problem when the wheels are off the ground.

EDIT: Also check your gearboxes. Clean the debris if there is any inside. We had a problem two years ago when the gearboxes were mysteriously locking up (we were using toughboxes). What we discovered was that one side of the gears has a little "lip" machined onto it to prevent it from rubbing against the plates. The lip needs to face the plates. See here. The side facing us right now has the "lip."

Post back tomorrow when you run the tests!

[Creator Mat]

We did some more tests and think we got to the root of the problem. Somewhere along the line our bumper perimeter got slightly misaligned and is causing the binding. The gear box was torn apart (twice) and the chain was re tensioned, but nothing chained. The "slow" side moved fine untill the bumper perimeter was put on. We will work some more on it tomorrow to get the kinks out. Thanks for the advice tho