[Rhubarb]

This year we have been plagued with what at first sounds like an electrical problem, then trouble shooting points us more towards a possible mechanical problem.

Here is what we have:
- Drive train is the kit base and transmission, 4wd run by 4 brand new CIM motors. (Gearing is a 21 tooth sprocket at the transmission, 28 tooth sprocket at each wheel) This is nearly identical to the setup we had last year and could easily run 2 matches without a battery change.
- Shooter motor is the large CIM motor spinning an axle with two wheelchair wheels. (It does not run continuously during a match, only when the kids pull the trigger.)
- A Fisher Price motor runs a set of rollers for the ball collector. (Normally off unless the operator turns it on.)
A van door motor run our turret. (Also normally off unless the driver is aiming.)
- We are using the 2005 fuse panel instead of the gold blocks because we want 40 amp breakers on all 5 CIM motors.
- Each motor has it’s own speed controller

The symptoms:
The first time we really drove was at the CT practice competition before ship day. During matches, the robot drive starts out fine but about ½ way through it begins to get sluggish despite having a brand new battery. Eventually we can’t turn or drive and it just stalls on the field. On the OI you can see our voltage drop from 13v to 5v or less. People running the playing field see the same thing. Bring it back to the pits and the battery has recovered back up to 12+ volts.

In the pits we can reproduce this by putting the robot up on blocks (no load on the wheels). Run just the drive motors (4 CIMS) full forward, then full reverse, the battery voltage drops dramatically and the robot controller restarts. You can run the robot full forward on the ground and hold it back with just your foot (not possible with last year’s setup). The bot will gently push, stall, reset the controller, push again, stall, reset, etc…
The problem seems to be pretty equal on both left and right side drive.

On the 2005 circuit breaker board there is a green LED that turns to red after almost every match. We have not been able to watch it closely enough to see exactly when it turns to red. However, if you run the dashboard program it says that none of the breakers have tripped.

Troubleshooting:
First thing we did was check the wiring and replace the robot controller. No change.
Just before ship we replaced this year’s transmission and motors with last years. Things seemed to improve for a short time. We could not get it to stall anymore with the push test and had much more reasonable pushing power. However, at the NJ regional the problem has come back.

Team 11 spent a long time with us in the pits in NJ (Thanks Guys!!!). We ran each CIM directly off the battery, bypassing all the electronics. We noticed that when you run just one CIM it spins at a certain RPM. Power up the second CIM in the transmission and it actually slows down the RPMs. This is true of both the left and right side, as well as the spare transmissions/CIM motors that we have.

We are aware that we have many motors and running all of them at once will drain the battery very fast. However, disabling everything else and using just the 4 CIM’s to drive should not be causing this big of an issue. Last match of the regional the drivers did not use any motors except to drive and we were still dead on the field after 1:30.

Any thoughts?