HO Shay 3 truck electrical pickup

[Patrick Durand]

Just installed a soundtraxx decoder plug in in three truck shay.   I tested the loco on DC prior to installation and noted a periodic stall as result of loss of electrical pickup. 

In the process of installing the decoder and speaker I removed all three trucks, cleaned the electrical wipers and mating bolster contacts with alcohol and then prelubed them with electrolube.   With the locomotive upside down, I connected one lead of my meter to the last wheel on the left side and then probed for continuity on the other 5 wheels on the left side.  These all tested indicating a continuous connection of all left side wheels even when the trucks were rotated and rocked back and forth.   Process was repeated on the right side.   This was done with the motor disconnected.

Wheels were cleaned, track was cleaned and the installation was completed.   Both electrical plugs going into the bottom of the water tender are secure.    Locomotive was put on the track and all the sound functions and operation checked out perfectly.

Here is the rub.   I like to run these locos at a walk.   Periodically there is a loss of electrical contact and the decoder resets starting the air compressor sequence.   On occasion the loco will stall at the same time.  The problem is not gears, it runs freely at all speads forward and reverse.   

It just erratically stops.  I can duplicate the problem by rocking the water tender to the right lifting the rear truck from the rail.  It is as tho the two front trucks are not picking up from the left rail.  Pressing down on the loco while tilting the tender will restore power and the pump starts running again.

By running the loco at an unprototypical high speed it will run all day without a glitch.

The problem is not a short as the DCS stays silent (no short indication).   It is an open circuit between the left rail and the decoder that occurs intermittently at slow speed in spite of having 6 wheels on clean rail.         The fact there is continuity among all those 6 wheels tells me the connection thru the plug between the coal bunker and water tender is secure.

Any ideas?

Pat Durand

[Yampa Bob]

Hi Pat
Sounds like you have done a thorough job of checking everything.  You might try placing the locomotive on a mirror to make sure all wheels are actually contacting the rails.  If you can easily slip a thin piece of paper between a wheel and the mirror, one of the trucks might be twisted or warped.

When you cleaned the track and wheels, did you use isopropyl alcohol, making sure there is no oil residue? 

That's all I can think of, perhaps others have more thoughts about the problem.

Good luck

[Cassshay10]

I have the coal version and was having the same trouble and noticed my oval track was in a bind. I fixed the bind and it now runs fine. Hope this helps

[Patrick Durand]

Thanks for your suggestions guys.  The intermittent power problem persists on the three truck shay.

Well, I have spent untold hours on the Shay, with the trucks off cleaning and leaded in the truck bolsters for more weight,  added weight to the locomotive and water tender.   The test track has been literally sanded from end to end.    A #2 pencil lead has been used to burnish the contact points with graphite.

Because the headlights go out at the same time as the stall, I have convinced myself that the problem is with the two wires red and black coming into the water tender thru the plug.   I'll give some thought to bypassing the plug and hard wiring the power leads and stuffing the extra wire up in the water tender just like the speaker is done.   I have not taken that drastic step yet.

It walks along just fine and then stalls with an open circuit.   I pulled the decoder out and replaced it with the jumper and I get the same problem of intermittent open circuit.   It will not go more than 6 ft without finding an excuse to reset the air compressor pump sound and occasionally stall.    NO Shorts as the DCS does not respond when these stalls occur.     

I have repeatedly plugged and unplugged both the jumper and the decoder on the 18 pins thinking maybe one of those was corroded and causing some resistance under load.

I have stressed the 2 wire plug going to the tender and it maintained continuity.

The locomotive is super detailed so there is no option of sending it anywhere.

I'll put it away for a few days and come back with a clear mind and start over.

Thanks to anyone with an idea where to go from here.

Pat

[Patrick Durand]

Thanks to Bill Van Bergen who operates three of these three truck shays a solution to the electrical pickup problem is at hand.    Bill commented that his shays had a tendency to derail easily on curves and he solved the problem by reaming the hole in the truck bolster out so the truck could rock side to side on the bolster pin.     Making the entire assembly more flexible so the wheels could maintain better rail contact seemed to be a step in the right direction.

I used a small round file to enlarge the bolster hole in the truck.   Keeping the file at about a 10 to 15 degree angle removes material from the bottom and top of the bolster hole.   Then I made up shim spacers from brass tube to form a shoulder on each bolster screw so it would tighten against the body bolster pin and leave the truck free to swing and rock side to side.

The improvement was immediate, and the shay now chugs  along taking five minutes to travel the 8 ft length of my test bench without stalling and starting the air compressor sequence on the Soundtraxx decoder. 

Thanks to Bill for the simple and what should have been an obvious fix that I was overlooking.