Hello everyone, I tried to search as best I could, but SW8 is to short of a search term... I have an SW8 that doesn't always like to start. Sometimes it just takes a healthy does of voltage and it will start, but other times it takes a physical push. I think the motor is 'stalling', for lack of a better term...any sort of movement that would shift the motor shaft slightly will set it free. I pulled the loco apart and cleaned and lubed it, and cleaned all of the electrical contacts and bent them slightly to increase the contact pressure, but none of this had any effect. Is this a common problem? It sounds like the overall opinion is that the SWs are good runners. Is there anything I can do short of changing out the motor? This is an unmodified DC loco. Thanks, Andrew
To determine if it is the motor itself I would pull the motor and apply current without anything attached. If it rotates freely in both directions then it is something else binding. If not could be some lube got into the motor brushes or on the armature. Also could be old lube gumming up the bearings. If you have an ultra sound bath, or a buddy that has one, a good cleaning of the entire motor with something like Dawn Detergent in warm water may clean it up. I keep some small jars with a dilution of Dawn in them and just pop the parts into the jar and then the jar into the ultra sound water bath. Cycle it about 30 mins. and then rinse well. Let it dry a day or two, gently lube the bearings only and reinstall. Dawn and water will not remove the varnish on the motor windings like some electrical cleaners will. Once that varnish is gone off the windings your motor is pretty much shot.
I have heard that the contacts for the moor aren't the most reliable. They are brass or bronze and attached to the shell. Sometimes they get loose and fall off, or wiggle and no longer touch. It might be that a push, jiggles things enough that it works for a while.
I have heard of guys who immerse the whole thing in water...and put power to it...to clean the motor ! Sounds odd and like it should short out...but I hear it works great. Maybe someone who has done the procedure can comment further. .
Thanks for the replies so far. More information: I stripped the trucks and body off of the loco and applied power to the frame halves, and the same thing was happening. Maybe 1 in 3 starts the motor needed a wiggle before it would start turning. I used my uncoupling tool to turn the flywheel just a hair to make it go. This loco hasn't really seen a lot of use, but I don't remember it doing this when I first got it. It then sat in it's case for a while...a few years perhaps.
The process is called "Water Dipping", and it is quite common in the RC Car hobby as a way to bed in the motor brushes on a new brushed motor.. When a running motor is placed in the water, the spinning armature does cause quite a bit of agitation in the water, so if you add a few drops of dishwashing liquid, this method can and will clean the motor... HOWEVER, doing so will cause excessive wear to the motor brushes... I have never tried it with a train motor, but the basic principal is the same.. Google "water dipping motor break in" if you want more information on the process..
I did some more investigating, and I think I know what is wrong. I think one of the poles in the motor is dead. That would explain it not wanting to start intermittently, when the bad pole is lined up. Also, the motor is not smooth when running. It's very smooth turning it by had, but it is fairly rough when under power. Could a dead pole simply be a dirty commutator? Is there a way to clean the commutator? Thanks all, Andrew
Check the motor for excessive end play, sometimes a out of round spacer will lift a brush off the commutator. A sticky brush can also cause the same problem. If a wire is broken, running the motor for just a few minutes should cause it to get hot! The best way to check it is to pull the worm gears, remove the brushes, and then remove the end bell. Check two poles at a time with an ohm meter, they should all be fairly close.
Unless you have a workshop with all the bells and whistles I would not get too fancy with trying to do all the testing advice along with motor disassembling. You may have simply hit on the issue of it sitting for awhile. The simplest thing to do is to clean the motor good staying away from the electrical cleaners because of the issue of removing protective varnish on the motor windings. Even if you don't have access to an ultra sound bath you can still do the warm water/Dawn Detergent in a small container letting it soak awhile and shaking the container. Rinse well several times and give it a day or so to be sure of drying out. Gently oil the bearing ends sparingly and trying powering it up. Its low tech and cheap and often solves the problems. Then if it still doesn't work and depending on the tools you have, and skills, try the other solutions, including simply ordering a replacement motor if available.
Andrew, That is exactly what I would have told you. I had the same experience with a Kato NW2. My bet it is that one of the tiny wires wound around the poles is broken. A very difficult fix in my eyes. I replaced the motor. I think I may have a spare SW motor kicking around. I'll look and get back to you. Clint
Yeah I have some hope that it is dirty or something and not a broken wire, since I'm sure it worked fine and smoothly before, but I can't be certain, it was a few years ago. I will try to clean it, we'll see how it goes. Are spare parts available for these? I tried looking on Walthers, but I didn't find anything. EDIT: Can anyone provide any instruction on removing the round brass motor contacts which I presume hold the springs and brushes underneath? I'm trying to avoid removing the worms and flywheel and bending the tangs to get the metal casing off.
These motors don't turn a lot of RPMs like slot car motors so I doubt it's a broken wire. The brush holders just pry out, I use a very thin screw driver. It helps to have a vice with soft jaws to hold the motor. I would not run the motor in water to clean it, good way to ruin your motor! This is really used to seat motor brushes quickly for a race car. I would remove the springs and brushes and use Alcohol to clean the commutator. Then use a can of air to get rid of any alcohol. Make sure both brushes are free to move in the holder. Use very little oil on the commutator side of the motor, to much will get on the commutator and brushes and cause it to run erratic. I never run anything on my motor brushes/commutator, it just gums up in the end. If you do decide to disassemble the motor you do not need to bend the tabs, the end bell will come off. In the end, if you damage it, then just purchase a new motor, at least you didn't just become a parts changer like everyone else!
More info: I pulled the brush holders out, and it appear that there was only a spring under one of them! That doesn't sound right to me. The motor does not appear to have been disassembled before, as it was unmarked until I had at it... Is the brush with no spring supposed to be oriented such that gravity holds contact with the commutator? Or is there supposed to be a spring in it? Now that I have the brushes out, what more do I need to do in order to test the poles? The holes are narrow and deep, I'm not sure how I'm going to go about cleaning the commutator...
I not aware of any that don't have the small springs for both brushes. Either it was a factory oops, or somebody else had the motor apart and lost it. And that could be the problem of the intermitant run. Then it may have been there and it was lost when you removed the brush. Danged things are tiny and can disappear in a flash. I've spent a lot of time on my hands and knees on the floor looking for such small items to only find them later on the work bench in front of me. I can't come up with a substitute off hand. A MT coupler spring is too light and a rapido coupler spring is too heavy duty for this use. If it did drop out unseen when you took it apart you could try a vacumn cleaner. I keep a small hand vac by the worktable and when I lose something and can't find it I make sure the vac is clean and then vac the floor. I then dump the contents on a white paper sheet and go through them with a pair of tweezers. Amazing what I recover that I didn't know I lost.
UPDATE: I fashioned a new spring out of some very thin copper wire, and now the locomotive runs without stalling. I'm certain it was missing one of the brush springs. The motor didn't show any signs of having been taken apart before I went into it, but I suppose someone with the right tools could probably do it without leaving witness marks. I'm not sure how long my homemade spring will do the trick, but it's working now. Thanks everyone for your help. Andrew
