Limit of the atwood motors?

Technical Motors
1

Team 753 had an interesting thing happen to our robot at PNW in the finals. One side of our robot wouldn’t move at all. Upon removal of the drill motor, the problem was quickly spotted: the plastic drill transmission was shattered. Thinking that was the only problem, we took our timeout and removed the drill motor, just leaving our atwood motor in there running solo. With just an atwood, we still would have been able to maneuver our way to the bar, and maybe even do some pushing on the way. We removed the drill motor in time, and put the robot on the field, but when the match started, the robot still only had 1 side working. The original problem was the atwood motor broke; I’m not sure how, maybe it was 9 straight matches, but the atwood was completely locked up, and the drill motor destroyed it’s transmission trying to push it. The atwoods were extremely hot when we took the robot out of the arena as well. I’m not entirely sure which problem caused which, but it is likely the atwood motor.

Is there any particular reason for this kind of catastrophic failure of the atwood motor?

2

It would be real interesting to take the atwood apart and see what happened inside there

I have seen the commutators on drill motors rip apart, tearing up the brushes and jamming the motors

Ive never seen an atwood fail - you might have the first one

let us know what you find

take photos and post them :^)

3

did your transmition have any pressure on the axis parallal with the drive shaft of the atwood?

4

I have toasted a few atwoods in bots running them at ~15v to ~24v and allowing them to draw in excess of 100 amps. I have noticed that they are relatively reliable once you open them up to cool. They do not seem to have a single point of failure. I have destroyed the brushes and commutator, melted the phenolic brush housing, and even smoked the windings. The oilite bushings have held up well even with axial and lateral missalignment. I would be interested to see how they failed.

5

I am guessing here, but as that motor heats up the bearing clearances probably start to close down and eventually seize the motor shaft. I am guessing that if you take the motor out after it cools, it will likely rotate fine. However, once the shaft has seized, I would only use that motor in an emergency. The bearings are damaged and the high heat has boiled the lubricant. Even if it works, I wouldn’t trust it any longer.

6

We had the same problem with our Atwood, but luckily it was during build season and not competition. We took the broken one out and put in a new one but still can’t figure out what happened to the broken one.

7

If either of you are going to Midwest Regional, can you bring the motor with you? I would like to tear it apart and look for failure point. If you open it can you take pictures and post?