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 Posted - October 03 2009 : 7:20:36 PM
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I haven't run my Mantua PC GP 20 for a while and I noticed today it ran better in reverse than forward. We talked about this before, I think, but I couldn't find the posts.
What are some reasons why this might happen?
Dirty track or wheels?
Bad electrical connection to track or bad track sections?
Thanks.
Alco Fan
Edited by - Alco Fan on October 03 2009 7:23:16 PM
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Posted - October 03 2009 : 11:46:29 PM
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i have an atlas (the southern sd24 i just did) that runs faster in reverse than forward. i have no idea why. i've had several tyco's do the same thing, & not all in the same direction.
jerry
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Posted - October 04 2009 : 12:13:52 AM
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It can be due to the commutator being turned slightly in one direction in relation to the armature poles, but the motors are aligned at the factory, and few ever have the commutator slip.
I think the most common reason is the way the brushes seat on the commutator, since we run them forward 90% of the time. You'd think that would make them slower in reverse, but most of the time that doesn't seem to be the case. Oil and dirt on the brushes can cause spongy and erratic behavior too, so keeping them oil-free is important.
I've also had some that start out faster in reverse, but after enough run-time they balance out, or even become faster in the forward direction.
It's interesting to note that the inexpensive can motors we often use for remotoring projects don't suffer from this problem, since every one I've used has had absolutely consistent RPM's regardless of direction, speed, or temperature. I think it may have a lot to do with the brushes being solidly mounted on bronze spring arms, instead of relying on coil springs and brass contacts for conductivity. My 2 cents.
The Tyco Depot
Edited by - NickelPlate759 on October 04 2009 12:15:08 AM
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Posted - October 04 2009 : 06:57:08 AM
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Thanks that's what I was after. All good points.
I'll check the brushes
Alco Fan
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Posted - October 18 2009 : 12:50:53 PM
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quote:We talked about this before, I think, but I couldn't find the posts
Originally posted by Alco Fan-October 03 2009: 7:20:36 PM
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I think the discussion you remember was specific to the Pittman motors in the die-cast steam locomotives. That problem can be resolved by shimming the armature where needed.
I can't seem to locate that post either, still trying to search for it. I remember only posting a link to an external site to give the guy credit for his work, so most of the keywords may not be here.
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