Tough Box Mini Micro Brownouts

My team has come to an issue where our tough box minis when being run are creating micro brownouts for fractions of a second causing the wheels and everything to jerk to a halt and go right back to running again. Also, one gearbox is much louder(Very loud) than the others and it seems to run faster than the quieter one meaning that the robot also doesn’t drive straight. If anyone has had this issue or has any idea or solution it doesn’t hurt to respond. Any response is a good response.

Had this issue running older batteries, have you tried using a relatively new battery?

There’s a couple of things you can do to check what the problem is:
[li]Is your wiring correct, and are there any wires hanging out somewhere where they shouldn’t? Double check to make sure your drive motors are in the 40 amp slots (even if that may not be the issue, the current draw should be high enough to warrant a 40 amp slot)
[/li][li]Is your gearbox assembled correctly? It’s possible that the gears’ teeth aren’t meshing correctly, and the grinding is causing the loud noise. The teeth could also be catching, meaning that your halt could be the gears catching on each other.
[/li][li]Have you tried a new battery? It’s entirely possible that your current battery doesn’t have enough power in it and is causing the brownouts.

Based on what you’re describing, I think that the second possibility is much more likely. If you were browning out, you would see things like the signal light flickering, as well as the whole robot stopping for a second. If that is the case, it’s an electrical issue. What I would recommend is disassembling the gearbox and reassembling it, making sure to follow the instructions carefully and then testing to see if the problem persists. (Also, don’t forget to grease your gearboxes too!)

Are your motor controllers wired to the PDP 40a slots?
30a slots will cause that kid of problem-they are too underrated for drive motors.
These cause an audible clicking noise as they interrupt the motor power.

I’ve experienced this problem on multiple occasions. Here is the rundown:

  • Not enough torque (due to wheels being too large in diameter)
  • Old batteries (as stated above)
  • Not charging batteries enough
  • Poor crimps for the motor controllers and battery (use a pneumatic crimper or a ratcheting crimper to fix)
  • Incorrect assembly of drive train or tough boxes (gears or axles are binding)

Your best bet is to eliminate the easiest variables and then tackle the harder ones if the problem persists.

Feel free to pm me if you need further assistance. Our team is only a 5 minute drive away!

We tested a few things before we ended our meeting today such as swapping motor controllers. Raising the robot off the floor and running it with no torque. Trying a different battery. Making sure each motor controller received a signal. And testing at low and high speeds. Doing one side at a time in both directions.
Thank you for all the responses so far. We will test the ones we haven’t tried tomorrow.

Have you tried all these?

Did you break them in?

Once you are convinced that it is actually assembled correctly, before you lube the gearbox, with motors mounted, turn the output shaft with a 1/2" wrench. It should be reasonably smooth, with not obvious tight or loose spots. If it is not I would strongly suggest you go through a break in process.

The tolerances and variations are pretty wide on toughboxes. We assembled two last night, one was fine, one was so bad that it would bog down a cim just trying to spin the gearbox, as the cim gear/main gear interface was way too tight. This is the worse one I have ever seen. We actually needed to clamp the back of the two cims together to get it to spin with a reasonable load, while we went through a breakin process. At this point I am not sure if we are even going to be able to use this gearbox.

Break in process is to assemble with no lube, and then run them dry, for an extended period of time (ideally under varying load). You will see metal “dust” as the gear interfaces wear in. We tend to do a “static” breakin, by just running the gearboxes direct connected to a battery for 45 minutes or so, with the gearbox and frame rail secured. There is often a visible pile of metal dust under the gearbox after this process. Disassemble, clean, lube and reassemble.

Check your 50 tooth gears for round. We had one gear a few years back that was out of round and when using 2 cims it would bind the gear between the pinions on the cims and the 50 tooth gear.

The gears, in these gear boxes have a very small shoulder on one side, at the shaft hole. One common problem, on assembling those gears boxes is to put the gears with the shoulder against another gear. The shoulder goes to the inner bearing race, away from the mating gear. Or, the gears should be flat together.

The result is the gear rubbing on the full face, of the bearing. And of course it won’t turn free.

We have had to correct a couple of gearboxes.

We had both gear boxes giving us issues this year (tight and noisy). We went through all the suggestions we could find including the break in process to no avail. We finally turned one of the CIMs 180 degrees and it was enough of a change to take the pressure off the 1st driven gear and quieted the transmission almost immediately. I’m guessing that the mounting holes on the motors are just a fuzz off. It took a lot of time nail down this issue. Hoping this saves others some time.

This is consistent with some of what we’ve experienced. If you overtighten the plastic case you can get that rattle. But while the rattle is concerning, we had this happen on a case back in 16, it functioned flawlessly the entire year. We recently scavenged the angled plates off that case (two years later) and could find no damage or unusual wear.

Having said that, it is good diligence to make sure there is nothing inside the case before putting it into service. Weve seen “good luck” charms in the form of loose extra gears left inside before by fabricators. Don’t undertighten the case but don’t crank down on the case bolts either.

We found that rotating CIMs 180 or swapping their placement in the box can make the difference between drawing 30 amps under no load to drawing fewer than two. Toughboxes are tough, but they sometimes are finicky.

You’re tripping the 40A breakers, that’s what a “micro brownout” to one side of the drive is. That’s what the clicking sound is.

Likely there is something mechanically off about the toughbox - are you sure you assembled the gears properly? (Remember, the ridge side should be the side contacting a bearing). Is everything tightened down? Everything lubricated? Does it spin fairly smoothly by hand?

The “loud” gearbox is probably the one running correctly, actually - the differences in noise are just going to be in speed more than anything.

It is almost definitely mechanical binding (or like, one motor completely dead, but that’s unlikely). Investigate the gearbox. It is probably not your electronics, especially since you already tried all that.