fyrstormer
RCC Addict
I've been running a custom Holmes Hobbies 11-turn 550 motor in a short-course truck for...about a year or so? Maybe longer at this point. I had some pretty severe growing-pains as I learned about brush compounds and spring tension, resulting in a totaled armature with a severely burned commutator. That's all in the past now -- the motor has been working well for months. However, I took it out for a run last night and it ran as though it had a dead coil in the armature, which happened before -- but then it started slowing down quickly and the motor completely stopped responding a few seconds later. There was no smoke, the motor was cool, and a test motor plugged into the ESC ran fine, so it wasn't a burned-out ESC. I took apart the motor to examine it, and I found the brushes and commutator to both be in a very strange condition. They had the usual wear-grooves on them, but in addition, the "smooth" areas between the wear-grooves were no longer smooth -- they were rough as if some kind of abrasive had suddenly gotten sucked into the motor and sandblasted both the commutator and the brushes. (there was no evidence of any actual abrasive powder inside the motor, for the record -- just the normal accumulation of brush dust.) In addition, the brushes are not excessively short, nor were they jammed inside the hoods, and the brushes did not spark excessively during a test-run after lathing the comm.
I was under the impression that Reedy 729 brushes are a copper/graphite composite, so I'm not sure what could've caused this kind of wear. After lathing the comm everything is back to normal, but if this happened once it could happen again, and I'd rather it didn't. Has anyone ever seen a motor where the brushes and comm both had a rough surface after a run, and more importantly, does anyone know what would've caused it? If nobody has any brilliant ideas, I might just switch back to Reedy Plutonium brushes in this motor, because I don't recall them ever having these kinds of problems, though I didn't use them very long in this motor before switching to the 729s. Maybe I'm just expecting too much from the 729s?
I was under the impression that Reedy 729 brushes are a copper/graphite composite, so I'm not sure what could've caused this kind of wear. After lathing the comm everything is back to normal, but if this happened once it could happen again, and I'd rather it didn't. Has anyone ever seen a motor where the brushes and comm both had a rough surface after a run, and more importantly, does anyone know what would've caused it? If nobody has any brilliant ideas, I might just switch back to Reedy Plutonium brushes in this motor, because I don't recall them ever having these kinds of problems, though I didn't use them very long in this motor before switching to the 729s. Maybe I'm just expecting too much from the 729s?
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