Problem with drivetrain and we can't figure it out.
 

A youtube video of the problem: https://youtu.be/eFp2-hd8kYI

In the description you will find timestamps with each event. If you guys have any ideas please let us know.

Re: Problem with drivetrain and we can't figure it out.
 

It's hard to tell exactly what the problem is, can you describe it?

Check how everything is wired. Can you guarantee that the wires from each motor go I to a separate speed controller, and nothing is accidentally crosswired?

Take a look at the LEDs on your speed controllers. You should see two light up for each side (note red/green for each!), Then running all of them forward you should see them all light up the same way they did when you ran each side individually. Do this without the motors hooked up to avoid having the breaker trip. That would rule out a code issue.

Are you sure your motors are going in the same direction inside each gearbox? If the polarity on a motor is reversed, you may be sending them in opposite directions, making them fight against each other.

Do you have a clamp meter you can use to measure each motors current while running? You may find that one or two motors are running "hot", helping you to narrow down the location of the problem.

Can you try running it without any belts? Misaligned belts or significant friction could cause armour issues.

Re: Problem with drivetrain and we can't figure it out.
 

We had a similar problem where either due to how the motors were wired or how it was programmed the motors were fighting in the Gearbox. They were spinning different directions. You can try to disable one motor at a time to diagnose.

Re: Problem with drivetrain and we can't figure it out.
 

Are you using Y cables to the motor controllers or individual PWM wires?

If you are not using Y cables, make sure that your code is sending the control to the correct PWM

You can remove circuit breakers for each of the motors and run each side 1 breaker at a time.

Re: Problem with drivetrain and we can't figure it out.
 

I noticed it said brownout protection on the dash whenever the problem occurred so we switched out the battery and everything seem to go a little better. We no longer loose connection from driving the 4 motors but out of curiosity how many CIMS can we drive at the same time at full power?

Re: Problem with drivetrain and we can't figure it out.
 

Test it, then look in the driving log to see what your battery voltage has been doing.

The Driver Station Log File is a really useful tool you need to get acquainted with.

On the Driver Station on the right side is the message window.
At the top left of the message window is a rosette icon.
Left-click on the icon and choose "View Log File"
That brings up the Driver Station Log File Viewer.

In the left window of the log file viewer you'll see a list of past robot runs.
Find an entry with the current date/time that's a reasonable number of seconds long and click on it.

The graphs for that robot run will appear.
The yellow plot line is your robot battery voltage.
Anything below 7v threatens a brown out.

You can also choose the Event List tab at the top of the graph window to see a list of warnings and errors that occurred during that robot run.

Re: Problem with drivetrain and we can't figure it out.
 

Check to make sure there aren't any wires crossing the CAN wires. We had that issue and the turned out to be the issue. Rerouting the wires away from each other may work.

Re: Problem with drivetrain and we can't figure it out.
 

There was a thread a few weeks ago about AndyMark transmissions. One side made a lot more noise than the other side. That happened to us. We followed their break-in procedure and when that didn't work, we swapped in a different gear housing.
Seems to be much better as a result. We also noticed a vibration coming from one motor, so we replaced it.

I also found a wheel bearing was pushed out when a student replaced the axles. Try pushing sideways on your wheels to see if they all have spacers. If there is a lot of wheel wobble, it could mean that a wheel bearing is missing or was pushed out.
Dave

Re: Problem with drivetrain and we can't figure it out.
 

It depends on a lot of things. Including the gear reduction, and weight of the robot - on top of that, if you have enough CIM's running, your robot will be able to move, but no for very long because it would drain the battery.

If you want a more technical answer (I could work the numbers for you, or document how to do it for you), let me know (reply, private message, or email). I recently did a bit of research into gear box design for the sake of an engineering project, and have developed some tools to allow me to quickly analyze a motor/gear ratio/robot weight combination. I also have a stack of references available if you would like to do your own research.

Re: Problem with drivetrain and we can't figure it out.
 

Replacing the battery fixed it oddly. Thanks for the help guys!

Re: Problem with drivetrain and we can't figure it out.
 

You should test that battery (3 amps for 2 hours while monitoring voltage works nicely).

Re: Problem with drivetrain and we can't figure it out.
 

How old are your batteries? We find they last maybe three seasons. We hold aside new batteries for competitions and dont use them for practice or debug. I strongly recommend investing in a "battery beak" http://www.andymark.com/product-p/am-0995.htm
We use it at the beginning of every season to test every battery.

Re: Problem with drivetrain and we can't figure it out.
 

It's very common to find the "low battery" issue causing a few posts every year on CD. It seems to take some teams a while to figure out that you have to charge the batteries often! And that the FIRST thing to do when you have odd, unexplained robot performance, is to glance at the battery voltage reading on the driver station. If it's less than 12.5 v when the robot is enabled, but not doing anything, then you need a fresh battery.