Router browns out with multiple CIMS driving WCD

[Tiago_MARS]

We have a 6 CIM West coast drive, and whenever we try to turn the router browns out. We tried dropping to 4 CIMS and it still happened. 2 CIMS worked, and we tried rotating out the motors so that wasn't the problem. If you turn the robot by hand it also turns easily and it doesn't appear to be a problem with the gearboxes. Each motor is pulling approximately 40-45 amps when in max load and we don't believe that would be normal in this type of drivetrain. Has anybody experienced this before?

[Ether]

Originally Posted by Tiago_MARS

We have a 6 CIM West coast drive, and whenever we try to turn the router browns out. We tried dropping to 4 CIMS and it still happened. 2 CIMS worked, and we tried rotating out the motors so that wasn't the problem. If you turn the robot by hand it also turns easily and it doesn't appear to be a problem with the gearboxes. Each motor is pulling approximately 40-45 amps when in max load and we don't believe that would be normal in this type of drivetrain. Has anybody experienced this before?

What kind of wheels?

What's the wheelbase and trackwidth?

How far did you drop the center wheels?

What's your gear ratio?

Put it up on blocks and tell us how much current it draws.

[Mark McLeod]

Did you look at the Driver log file to see how low the voltage was pulled?

[Tiago_MARS]

Originally Posted by Ether

What kind of wheels?

What's the wheelbase and trackwidth?

How far did you drop the center wheels?

What's your gear ratio?

Put it up on blocks and tell us how much current it draws.

We're using the AndyMark 8" pneumatic wheels

It's a 6 wheel drive. The wheels are 12.5" apart.

The center wheels are dropped 1/8".

Not sure about the ratio but it's the 2.06 spread for the 3 CIM WCD from West Coast Products. With an 11 pinion input.

It's pulling 10 amps on the blocks, but if you reverse directions it goes over 50

Also, when it drops out the voltage drops under 9.

[Ether]

Originally Posted by Tiago_MARS

We're using the AndyMark 8" pneumatic wheels... The center wheels are dropped 1/8"..

1/8" may not be enough for pneumatic wheels.

Originally Posted by Tiago_MARS

It's pulling 10 amps on the blocks, but if you reverse directions it goes over 50

Full throttle?

The numbers are ambiguous and seemingly inconsistent:

10 amps total divided by 6 motors would be only 1.7 amps per CIM, which is less than their free amps.

50 amps per motor times 6 motors would be 300 amps, which would pop your main breaker.

Please elaborate.

[Mark McLeod]

The robot radio shouldn't brownout until ~4.5v if it's wired to the VRM.

[Tiago_MARS]

Originally Posted by Ether

1/8" may not be enough for pneumatic wheels.



Full throttle?

The numbers are ambiguous and seemingly inconsistent:

10 amps total divided by 6 motors would be only 1.7 amps per CIM, which is less than their free amps.

50 amps per motor times 6 motors would be 300 amps, which would pop your main breaker.

Please elaborate.

Yes that was all per motor, but only 4 motors are on right now. It was also full throttle. However the 50 amps were only a spike as we reversed direction so the breaker didn't pop because it was instantaneous.

Also we thought about the 1/8" not being enough but it has worked previously, we are only experiencing this today. Also its pulling these amps on the blocks so the wheel drop shouldn't affect the amps right now...

[Ether]

Can someone please comment:

For a 4 CIM West Coast drive, is 10 amps per CIM par for the course for full throttle up on blocks?

How about 1/8" center drop for 8" pneumatic wheels?

[Chris Mounts]

We're running a similar setup. We've got the 8" pneumatic wheels, WCD gear boxes with the same gear ratio (I think), 3 CIMs each side, and a 1/8" drop. The only difference is our C/C of wheels is about 7.9". We're driving and turning without an issue. I'm sure the larger C/C distance isn't helping but I wouldn't think it would cause consistent brown outs though.

Can you compress the C/C distance?

Not sure about the current. Never checked on blocks.

[Bob Steele]

We are using 8 6" pneumatic wheels and 6 CIMs and are using a 3/16" drop this year because of the pneumatic wheels.

You might also take a look at what pressure you are using in your tires.
Higher pressures would probably help with scrubbing.

We are also current limiting in the program to maintain voltage to the RoboRio.

[Tiago_MARS]

Well we found out through the VRM that it is in fact not the radio but the RoboRIO that is browning out. There isn't a very easy way to change the drop or the C/C without redoing the entire chassis and I don't think that would be necessary since it had already worked earlier in the week.

[PayneTrain]

Originally Posted by Bob Steele

We are using 8 6" pneumatic wheels and 6 CIMs and are using a 3/16" drop this year because of the pneumatic wheels.

You might also take a look at what pressure you are using in your tires.
Higher pressures would probably help with scrubbing.

We are also current limiting in the program to maintain voltage to the RoboRio.

We've been running 3/16 and a high difference in pressure between the center and outer wheels and we have been pretty good. One of these changes is easy and the other probably is not.

[Ether]

Originally Posted by PayneTrain

high difference in pressure between the center and outer wheels

difference in what direction?

[Chris Hapstack]

Originally Posted by Ether

difference in what direction?

I think the trend has been over-inflating the center wheels and under-inflating the front & back wheels, which kind of adds to the drop center effect. But of course I can't answer for 422.

[Tiago_MARS]

Fix! Well that was interesting. There was a fault in the PD board (orange light) so once we cleared it it seems to work as expected. Thanks to everybody though!