HELP: Voltage Drop

[Ether]

Originally Posted by billbo911

what bothers me with the OP's issue is how two motors on the same transmission could have such a huge temperature difference

Originally Posted by Ether

Agreed.

Originally Posted by billbo911

1 gearbox per side with 2 CIM per gearbox - front CIM gets hot. No way this should happen

Resolve the issue of whether or not the front and rear motors are actually getting the same voltage. Measure it. This is not difficult to do.

[pujan824]

Originally Posted by Ether

Resolve the issue of whether or not the front and rear motors are actually getting the same voltage. Measure it. This is not difficult to do.

Yes, they are getting the same voltage

[Ether]

Originally Posted by pujan824

Yes, they are getting the same voltage

Please tell: How did you measure it?

[billbo911]

I'm going to talk about just one gearbox for now.

Both motor controllers in a gearbox are getting the same control signal according to your code.
Both motors are receiving the same voltage from their respective controllers.
One motor is hot while the other is room temperature.

You can see why this is so difficult to address. The illogical is happening.

At this point, I would have to say there is a mechanical difference between these to motors. Something like: one is using a 12 tooth pinon while the other is using an 11 tooth.

Sorry, without more details, I really am stumped by this issue.

[pujan824]

Originally Posted by billbo911

I'm going to talk about just one gearbox for now.

Both motor controllers in a gearbox are getting the same control signal according to your code.
Both motors are receiving the same voltage from their respective controllers.
One motor is hot while the other is room temperature.

You can see why this is so difficult to address. The illogical is happening.

At this point, I would have to say there is a mechanical difference between these to motors. Something like: one is using a 12 tooth pinon while the other is using an 11 tooth.

Sorry, without more details, I really am stumped by this issue.

That could be it. While practicing on a floor we could run 20 minutes or more until the battery dies and the motors don't get hot at all despite going over some obstacles. I'm stumped on this issue too. This has happened on our robot from last year as well. Unfortunately, our robot is all bagged up and we won't be able to check until our competition

[Al Skierkiewicz]

pujan,
If you are simply using joystick code to control the motors then you need to calibrate the controllers to be sure they are being fed the current input. If you are sure you are sending the exact same coded input to each motor controller then it is possible you have a mechanical issue in the transmission. This is often a motor misalignment or the keeper that holds on the pinion gear has been pushed against the transmission case. About 100% of the time, the transmission makes noise to tell you something is wrong. The only way to be sure is to disassemble the transmission. I know that sound like bad news, but you have to get to the bottom of your problems and correct all.
While there is nothing you can do right now on the robot, you can plan your work for your competition. Work efficiently and plan exhaustively. I think by now you know you will need a wheel change for at least the outside tires. If nothing else, you could run the current style wheel on a lathe and turn down the outer diameter. That is the same as dropping the center wheels when you think of it. Remember you are able to bring in 30 pounds of fabricated items for your withholding. Ask you close teams for assistance, the veterans may have wheels laying around they could let you have.
Also check all electrical connections when you take the robot out of the bag. You want all #6 wiring tight, secure and insulated. That means checking the hardware on the batteries, the main breaker and the PDP. Ask you LRI for assistance, they have lot's of experience and can usually spot something in a few seconds that you have been scratching your head over for weeks.

[gpetilli]

Originally Posted by billbo911

I'm going to talk about just one gearbox for now.

Both motor controllers in a gearbox are getting the same control signal according to your code.
Both motors are receiving the same voltage from their respective controllers.
One motor is hot while the other is room temperature.

You can see why this is so difficult to address. The illogical is happening.

At this point, I would have to say there is a mechanical difference between these to motors. Something like: one is using a 12 tooth pinon while the other is using an 11 tooth.

Sorry, without more details, I really am stumped by this issue.

I will be even bolder and say there is a key missing on one of the CIM gears.

[pujan824]

Originally Posted by Al Skierkiewicz

pujan,
If you are simply using joystick code to control the motors then you need to calibrate the controllers to be sure they are being fed the current input. If you are sure you are sending the exact same coded input to each motor controller then it is possible you have a mechanical issue in the transmission. This is often a motor misalignment or the keeper that holds on the pinion gear has been pushed against the transmission case. About 100% of the time, the transmission makes noise to tell you something is wrong. The only way to be sure is to disassemble the transmission. I know that sound like bad news, but you have to get to the bottom of your problems and correct all.
While there is nothing you can do right now on the robot, you can plan your work for your competition. Work efficiently and plan exhaustively. I think by now you know you will need a wheel change for at least the outside tires. If nothing else, you could run the current style wheel on a lathe and turn down the outer diameter. That is the same as dropping the center wheels when you think of it. Remember you are able to bring in 30 pounds of fabricated items for your withholding. Ask you close teams for assistance, the veterans may have wheels laying around they could let you have.
Also check all electrical connections when you take the robot out of the bag. You want all #6 wiring tight, secure and insulated. That means checking the hardware on the batteries, the main breaker and the PDP. Ask you LRI for assistance, they have lot's of experience and can usually spot something in a few seconds that you have been scratching your head over for weeks.

Majority of that 30 pounds we can have off is used up by keeping our shooting mechanism off and improving it. I doubt we have enough weight to have anything else

[philso]

Originally Posted by pujan824

Majority of that 30 pounds we can have off is used up by keeping our shooting mechanism off and improving it. I doubt we have enough weight to have anything else

Do you have the budget to purchase one or two new gearboxes? Are the gearboxes in your robot accessible such that you can swap them out with new ones?

The Toughbox Mini gearboxes are considered COTS parts. If the gearboxes come assembled, you can bring them in as is. If they come disassembled, you would have to bring them in to your tournament in the disassembled state to count as COTS. If that is the case, make contact, ahead of time, with one of the many veteran teams that will be attending GTRE. Ask if they can provide an experienced team member help your team assemble the gearboxes at the tournament. Preferably, find a team with someone who has direct experience with the gearboxes you are using. It may also be possible (maybe easier) to find a team NOT competing at GTRE to send someone to help you for a day.

Best of luck.

[pujan824]

Originally Posted by philso

Do you have the budget to purchase one or two new gearboxes? Are the gearboxes in your robot accessible such that you can swap them out with new ones?

The Toughbox Mini gearboxes are considered COTS parts. If the gearboxes come assembled, you can bring them in as is. If they come disassembled, you would have to bring them in to your tournament in the disassembled state to count as COTS. If that is the case, make contact, ahead of time, with one of the many veteran teams that will be attending GTRE. Ask if they can provide an experienced team member help your team assemble the gearboxes at the tournament. Preferably, find a team with someone who has direct experience with the gearboxes you are using. It may also be possible (maybe easier) to find a team NOT competing at GTRE to send someone to help you for a day.

Best of luck.

Getting to the toughbox is going to be a challenge. It will make us have to disassemble our entire robot just to get to it. Our mentors are skeptical to the problem and do not want to disassemble the robot mainly due to the time it takes to re-assemble it. But we have a couple extra toughbox minis and cims that we know work properly. The only problem we would have is getting to the gearbox and replacing it.