drive train wearing out?

[EricH]

Originally Posted by imdunne8

First off, the launcher and drive motors are on separate fuse panels (drive motors on 40A maxi block, launcher on 30A). I second that the problem is not an electrical connection problem, though we are going to check to make sure when we get to Atlanta.[...]
I am personally leaning toward our CIM motors going bad because our lifter, which is using the Taigene motor, seems to still be functioning perfectly. Has anyone else ever run into CIMs going bad after quite a bit (I would guess at least 15-20 hours) of running their robot?

An electrical problem could be farther up the line. Check the distribution block.

I don't think you can kill a CIM in a mere 15-20 hours. 330 has been running their practice robot for I don't know how long and hasn't killed a CIM yet that I know about. Wheels, yes, motors, no.

One other thing--did you change the code at all?

[JimWright949]

One of our joysticks was wearing out and not sending solid(ish, well as solid as these joysticks can) signals. Double check your Joysticks for your drive issues.

-Jim

[gurellia53]

Originally Posted by JimWright949

One of our joysticks was wearing out and not sending solid(ish, well as solid as these joysticks can) signals. Double check your Joysticks for your drive issues.

-Jim

We're getting a full command sent to our victors (solid LEDs)

[Kevin Sevcik]

I'm really leaning towards a sneaky electrical problem in the high current path as well. As noted, it's really rather difficult to kill CIMs, especially to kill them as much as you claim to have done. Having a robot act strange under high current draws is pretty darn easy, though. The fact that your other motors are working fine doesn't really change anything, as they don't sound like they're drawing very much current at all.

I'd really, really recommend checking you connections, as it's really the only thing those two systems have in common. I can't imagine your launcher motor was running for the exact same time your drive motors were. I'd bet it was running 25% of the time or less, so it should have deteriorated much more slowly.

If you really can't be bothered to check all the connections first, you can do a quick check with a pair of multimeters. Measure the voltage across your battery and across the V+/V- terminals of your launcher's speed controller while the launcher is loading. I'd recommend doing the drive wheels as well, but you need some way to safely load them while the robot isn't moving. The difference you see is entirely dependent on how much wiring you have and how good your connections are, but I don't think it should be more than 1.5V. Maybe 2V. I'm sure the other experts in this thread with have good suggestions for values, but you're dropping 2 or more volts on the way to your speed controller, you definitely have a problem in the power path.

[MrForbes]

If you really can't be bothered to check all the connections...you probably should not have asked for help????....

Seriously, just because you don't think this is the problem, until you actually check the connections (really check them), you won't know if they are OK or not. You have described symptoms which are commonly caused by poor power distribution connections, so it would be time well spent seeing if that is the cause, even if you have never experienced this situation before--others have, and several folks here zeroed in on this as the most likely culprit.

[Erich & Posse]

We had a similar problem, robot would work fine but sometimes it would stop then jerk once in a while. found out that our battery connections were bad. between the AM cables and the actual battery terminals, make sure the bolts are very tight and wrapped in a lot of electrical tape.

[gurellia53]

Originally Posted by squirrel

If you really can't be bothered to check all the connections...you probably should not have asked for help????....

Seriously, just because you don't think this is the problem, until you actually check the connections (really check them), you won't know if they are OK or not. You have described symptoms which are commonly caused by poor power distribution connections, so it would be time well spent seeing if that is the cause, even if you have never experienced this situation before--others have, and several folks here zeroed in on this as the most likely culprit.

Sorry if I seemed ignorant of the power distribution. Like I said, I'm not even on the electrical team. It's definitely something we'll look at.

It sounds like its an electrical problem which hopefully wont be too difficult to fix. If I'm understanding this right, a lose connection would increase resistance in series with the motors and dropping the voltage available to them. Also, it might lose contact and cause a momentary loss of power to the motors. Is this correct?

Thanks to everyone who has responded so promptly!

[MrForbes]

Originally Posted by gurellia53

If I'm understanding this right, a lose connection would increase resistance in series with the motors and dropping the voltage available to them. Also, it might lose contact and cause a momentary loss of power to the motors. Is this correct?

Yes, that's correct. The result is bizarre behavior from the robot.

[Qbranch]

Our robot's odometer reads a little under 75,000ft on it's drivetrian now (about 14.2mi ) and the chains have started to gum up from carpet fuzz (among other things).

Our (currently tired) robot is due for an overhaul that we'll be doing thursday morning in Atlanta. It'll be back up to it's old midwest-regional-speed self first thing Thursday.

But yeah, you are not alone in your robot's symptoms gurellia53, they aren't much different from the ones ours developed.

Good luck finding your problem,

-q

[Jim E]

W are experiencing similar issues too. The Electrical paths is one of the items we will address at Atlanta before anything else.

I want to add that the Ground returns are just as important to check along with the power side.

All of those return molecules have to go somewhere. Think of a Dam.

If the water leaving the dam is restrained, it backs up behind it. If the dam is wide open and the water to the dam is a trickle, the same amount of water is still leaving the dam. The trick is figuring out what scenario is happening. Sometime heated wires can pinpoint where the problem is occurring.

At the Florida Regional, we must have redone connections on the battery terminals at least 5-6 times. Those screws would work loose and then you would have a resistance build up or intermittent connection. That surprised me the most. If you think a connection is tight enough, give it another 1/4 turn for safe measure.

The yellow jumper may also be an issue on the distribution block. Move your wires around so the maxi-block is fed by the same block as the power coming in without the yellow jumper being a factor.

All of our other wire connections are soldered to minimize resistance, so the focus will be from the maxi-block back to the battery.

[IndySam]

Originally Posted by EricH

An electrical problem could be farther up the line. Check the distribution block.

I don't think you can kill a CIM in a mere 15-20 hours. 330 has been running their practice robot for I don't know how long and hasn't killed a CIM yet that I know about. Wheels, yes, motors, no.

One other thing--did you change the code at all?

You can easily kill a CIM in 30 minutes if it gets too hot.

Lot's of practice without proper cooling time will greatly shorten the life of your motors.

But I would agree that it's more than likely a connection problem.

[imdunne8]

Well if it helps at all, we were seeing temperatures of around 150 degrees farenheit using a non-contact thermometer after a decent amount of use. This was the temperature of the casing of the motor, so it could have been hotter in the center.

Thanks so much for all of the replies so far. We will definitely be putting a lot of effort into the robot on the practice day in Atlanta. I'll be sure to check everything you guys have recommended. The only reason I am thinking that it is not a loose connection is that we have noticed a significant difference in the drive motors, a smaller difference in the launcher motors, and no difference in the lifter. As some have said though, the lifter gets very little use.

[bobdahaxor]

We had that SAME EXACT problem with our drive train. We used a direct front wheel drive 1 CIM per side configuration with traction wheels. (We had omni's in the back) Our issue was we would test on our hard linoleum surface and be fine. We also tested at the play date. We were fine (but we only ran one match per trial). We got to Chesapeake and nothing worked. If you use a Gyro, disable the gyro code and any other sensors that would affect your drivetrain. These could be hindering your turning ability because they attempt to control the spin and causing you to be unable to turn. When the motors are cool, I bet you have decent performance. As motors heat up, the become less efficient causing more power to be drawn. Did you ever notice a "stuttering"? This would be caused by circuit breakers popping and resetting. If possible, I would strongly consider changing your gear ratio or between matches putting ice packs on all of your motors. We did this with great success at Philly and I think it can work for your team too!

[gurellia53]

Thank you everyone!

I think we'll plan on changing the motors (we have to open the transmissions anyways) and check for loose wires. We also have some sort of a thermometer on our multimeters (how awesome is that ) so we'll probe around for hot spots. Also, not mentioned in this thread, some people on our team think that we may have bad victors. And since we have 2 empty victors on our robot, we'll switch the drive motor victors.

Al, thanks for your offer! I'll definitely look for you in Atlanta.

-Andrew

[RyanN]

I haven't seen anyone throw this out yet, but you should also check your Victors. A few years ago, our robot had a weird issue of driving very weird in forward, but perfectly in reverse. When I took the fan off the victor, I saw that one of the transistors was blown, causing less power to go to the motor. With the stress of one motor driving the robot, the Victors take more abuse, which may cause them to fail.

To check this, just pop off the fan, get a small flash light, and look at each transistor and see if there are any pieces missing from them. Also check for melted plastic where the transistor enters the case. This is also a sign of something wrong.