#69 Track Maintenance Car Problem

[gottcent]

I have a postwar #69 track maintenance motorized unit that runs well in one direction but only runs in fits and starts in the other (i.e., it's not dead in the other direction, but far from healthy). Here's what I've done so far: cleaned the commutator face and brushes, oiled the wheels and armature shaft (with the ball bearing in place), cleaned the ground contact points on the removable plate, cleaned the ground contact spring, and bent the spring a bit to make sure it was making good contact. I also tried applying a lead from my transformer to the pickup roller and then the other lead directly to each ground contact terminal in turn. In the first case, the motor runs fine, but when I apply a lead directly to the other contact terminal, I get the same fits and starts. That leads me to think it's not a bad connection between the grounding spring and the contact point. What else could be causing this problem, and what can I try to correct it?

Thanks in advance for any tips.

John Gottcent

[cwburfle]

Are you certain that the "fits and starts" are being caused by an electrical problem?
I ask because it's possible that  you have binding in the mechanism.
As the armature turns, the worm pushes the worm gear to one side or the other, depending upon the direction.
It is fairly common for the bearings to wear, allowing the backs of the wheels to rub on the frame, causing binding.

If this is your problem, some folks like to slip a c-clip behind the wheel.
Sometimes I like to pull the wheel and put one or two 671M-23 washers between the wheel and the frame.
Another alternative is to replace the bearings.

 

[KRM]

 

How much run time is on it?

 It sounds to me like it could have short motor brushes if it is working in one direction and not the other. Been there and seen that. You see in one direction the worm gear in the motor is pushing the armature up against the brushes and in the other direction it is pulling it away from the brushes. I think in reverse it is pulling it away and short brushes will not make good contact the other way it is pushing it up making better contact.

 Just a thought.

[gottcent]

Thanks for your thoughts, guys. I'll give both your ideas a try and let you know what happens.

John

[gottcent]

OK, I tried placing a C-washer between one of the driver wheels (the one that looked like it might be binding) and the frame. I also decided to add a little oil to those driver wheel axles. Voila! It now runs in both directions. Ironically, the washer soon fell out, but the unit still runs both ways, so the lube job must have done something. Thanks for that tip.

However, another problem has developed. In the new "reverse" direction, the unit runs fine. But in the other direction (the one that has worked all along), it now stalls after about 15 seconds of running. I've found out why--the reversing bar is a bit loose in that position, and the jostle of the car's movement shifts it back about 1/8 inch--just enough to put it into neutral. By pushing the reverse bar by hand, I can start it up again, but after another short run, the same thing happens.

I've tried bending the ground spring into various positions to see if I can get it to hold better, but no luck. I've also thought of "extending" the ground contact point involved a bit with a little solder, though I would have to be careful not to apply too much. I'm assuming the problem is that the contact point is not holding the ground spring firmly enough in that direction. If you have any other ideas, I'd love to hear about them

Thanks, John