Recently purchased an old PFM Santa Fe class 4100 2-8-4 with an open frame motor in questionable condition- put it on the track, gave it 8 volts, no current draw and no motion. Disassembled it, found a broken wire that had been repaired with masking tape. Cleaned it, resoldered the wire and covered the joint with electrical tape, lubricated it, and it ran reasonably well at 8V. But as I was testing it, it started to short at switches, and the on straight track, just a bit at first, but progressively worse, to the point where it shorted when I opened the throttle. Like a lot of old brass, it uses the tender for the current draw, so I checked the tender and engine independently, to ensure the short isn't in the wheels- but still no luck.
Any ideas what this might be?
http://mprailway.blogspot.com
"The first transition era - wood to steel!"
Could be a lot of things.
The first two items I check are the insulated wire in the back of the cab, and the brake shoes.
The wire from the tender drawbar through the cab has an insulated bushing that can break down, or the wire can rotate and contact the cab.
The brake shoes should have 0.020" clearance from the drivers.
Hopefully it is this simple.
-Kevin
Living the dream.
It's also possible that the front pilot wheels are shorting to the underside of the frame. I discovered that issue with an OMI 2-8-2 Heavy Mike I purchased a few years back. Fixed it with Kapton tape.
Speaking of which, you should really get yourself a couple of rolls of Kapton tape - e.g. 3/8 & 1/2" widths. It's SO much better than electrical tape in that it's thinner, stronger, and doesn't leave behind ANY gummy adhesvive when it get's old or warm. You might also want to invest in some various-sized heatshrink. It insulates small OD wires much better than electrical tape.
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
tstageSpeaking of which, you should really get yourself a couple of rolls of Kapton tape - e.g. 3/8 & 1/2" widths. It's SO much better than electrical tape in that it's thinner, stronger, and doesn't leave behind ANY gummy adhesvive when it get's old or warm. You might also want to invest in some various-sized heatshrink. It insulates small OD wires much better than electrical tape.
Great advice. Both of these items should be in your brass-operator's tool kit.
Both can be purchased from Amazon, in lifetime supply quantities, for less than $25.00!
Check all the tender wheel sets for being installed the right way round. Two rail wheel sets have one wheel electrically common with the axle and the other wheel insulated from the axle. Electrical pickup from the wheels is done thru the axle. If one wheel set in in backwards you have a short.
David Starr www.newsnorthwoods.blogspot.com
Also with older brass there can be insulation around the hub of one of the drivers and has to be replaced on occasion, not an easy job and your problem has the same simptons.
BTW, I repair and tune older brass. Just finished waking up a beautifully painted PFM/Fujiyama RF&P 4-8-4 for a local gentleman. If she exceeds your abilities to get her up to snuff. Shoot me a message. Brass does have the knack of creating lots of frustration. One trick is to try running with the lights off in the room, then look for the spark where there should be no spark, that is where things are touching that shouldnt be. Sometimes its pipe work, a pilot that is slightly bent downwards letting pilot wheels touch, trailing truck side frames or wheels catching all the plumbing that hangs down below the cab or internal shorts of things touching that should not. Mike the Aspie
Silly NT's, I have Asperger's Syndrome
Yes, unfortunately, the short could come from several places. Put on your detective hat and try to eliminate possibilities: separate the tender from the engine and see if it is one or the other. If it's the tender, check the orientation of the wheels as mentioned above. I'm guessing it's the engine: if that's the case, remove the boiler (screws should be at both ends of the engine - you may have to remove the lead truck) and look for a loose wire or anything else obvious. Put the engine on the rails without the boiler and check if the there is still a short. If there is, then there is a chance that it is the driver wheels, as mentioned above. Some makes insolate one side of the drivers with bushings that can wear out.
Simon