JPD OK, problem solved. I took out my multi-meter and checked for continuity to try and determine how the pilot wheels were shorting out. Basically, I discovered that if the front right wheel was pushed up and touched the frame of the locomotive a short would happen. In fact, at this spot I saw that the paint was rubbed away. I went back and checked the track and at the trouble spot I saw once I got down at eye level that one rail was indeed higher than the other, barely noticeable. I slipped in a small styrene shim and the problem goes away. That was a fun waste of two days, but I guess I learned!
Simon
We haven't seen him out in the open here for a while (is he in the coffee shop?), but cudaken had a bad experience with his PCM Y6-b 2-8-8-2, which he loved. It kept shorting suddenly, after many hours of use. He eventually found the short related to the pivot for the front engine, if I recall, or maybe it was contact with the massive from cylinder, I forget.
It seems that our scale locomotives follow largely the same pattern of dissolution that the real things and our automobiles follow. Over time, they develop more and more thorny problems.
One thing I've noticed in model railroading is there seems to be a kind of inverse ratio regarding problems - the simpler the solution turns out to be, the more difficult it is to figure out the problem.
Funny how problems can pop up with no warning. I have a brass 2-8-0 that ran flawlessly for years. Then one day it would short only going around one curve but no where else. Careful examination showed one driver brake shoe would touch when the drive axled moved laterally. I have since replaced them with resin cast shoes. Problem solved.
Glad you got to the bottom of it.
Pete.
Glad you were able to dope it out. This will be a useful post for modelers perplexed by inexplicable pilot shorts in the future.
-Matt
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
Here is the situation. I have a BLI 4-6-2 that shorts out on a particular spot of track only going in one direction, forward, reverse is fine. When I turn the room lights off and carefully observe what is going on I can see a spark on the lead wheels of the pilot when it reaches this particular point. Here is what I have done to troubleshoot the problem:
1.Tested a second BLI 4-6-2 over the same section of track and going in all directions and it runs through with no problem, as does a BLI 2-8-0.
2.I checked with the NMRA gauge the tracks and pilot wheels and everything is in gauge.
3.I removed the pilot from the troubled locomotive and the locomotive runs fine over the track with the pilot wheels removed.
4.In addition, the removed pilot runs fine over the track on its own.
5.I carefully inspected the removed pilot and can see no obvious flaw. I also compared it closely to the pilot on the BLI 4-6-2 that is running fine and see nothing unusual.
6.I cleaned the track in the problem area, but that did not help.
I should add that I am using a Digitrax DCC.
Any ideas? I am stumped by this one.