I have been in the hobby off and on for about 60 years. I have never replaced any brushes or brush springs. I have taken them out and given them a thorough cleaning, but I have never replaced them. My questions are:
1) What problems are cured by replacing brushes and/or brush springs?
2) what are the symptoms of brushes that need replacement?
I have a couple of engines that growl occasionally and I'm wondering if brush replacemnt might be indicated. Both engines have been completely lubed including oil on both ends of the armature.
Earl
I restored a 252 lionel engine and it went around the track at a slow speed. I replaced the brushes and springs and now it zooms all about. A good way to see if they need it is to rub them on a fine grit sandpaper like you are cleaning them. If they leave a big black mark, it is time to replace - Just a little mark and they are fine. My 44 ton was doing okay but I replaced the brushes in it and now it rund like the day I got it.
On the American Flyer engines old style motor, the brushes are about ¾” long, and as the wear get shorter. I have seen some very worn brushes that still work well as long as the contact spring maintains sufficient contact pressure against the commutator to provide the correct balance of conductivity / drag. I have had some brushes that were of sufficient length and contact pressure, but once replaced the engine ran better. I have not tested this but I wonder if the brushes are to a degree porous and when an owner over oiled a motor, saturated the brushes to impede current flow? Brushes are so cheap I usually replace them whenever I get a loco to work on.
Jim
It comes down to better electrical contact. The spring is the key. Worn and aged, they have no tension. A short brush means the spring has to expand more and looses tension. The quality os a good brush is it's length (age related), flatness,and Is the contact surface square with length.(indicates worn sides). I actually have a pair like that.
I have cured my engine growling by lubing the spinning armature.ends
Bob
Yep I need some springs and brushes.
I sparingly replace motor brushes and springs. Usually, the brush has to be down to a nub or a spring broken before I do. There are some repair folks that advocate routinely replacing brushes and springs because they are inexpensive. The few times I recall replacing them was due to erratic motor operation (speeding up and slowing down at the same transformer voltage). I don't know that worn brushes and springs would cause a motor to growl, but you could always try it to eliminate that as the problem.
Robert
http://www.robertstrains.com/
I'm thinking that some folks might be getting better operation from new brushes because the new brushes are cleaner then the old brushes. I clean my brushes and brush housings thoroughly and I dress the contact end of the brush lightly before re-installing the brushes. I also check the springs to insure that the brushes make good contact with the armature. I doubt if new brushes would help in the situations I have encountered.
Jim, I don't see how oil in a porous brush could increase its resistance. If oil can get into it, it will be displacing air, which is no less an insulator than the oil. If oil has any effect, it has to be at the surface of the brush, perhaps collecting dirt.
Bob Nelson
Good point. It's not the oil but the oil trapping the dirt andperhaps clogging the commutator segments.
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