Amperage spike & DCS signal loss at one spot on layout with only one engine

I don’t have the answer to your question, but I must commend you for a very detailed, accurate, and precise explanation of your problem.  This is in stark contrast to the folks who would describe this by saying, “My train shorts out on the curve.” and expect someone to figure it out from that paltry bit of information.

Somebody will have an answer for you, I’m sure.

I would not keep doing this. I am not sure what is going on or why yet.

I'm tempted to think this engine may have a short that occurs on this curve. Why not on other curves though? why only in one direction?

@VonFrank posted:

...

- Faces one particular way

- Traveling one particular direction

- At only one specific curve on the layout

This engine does not cause the spike anywhere else. Other engines do not spike the amperage anywhere at all on the layout, including this spot. This engine does not cause the spike when traveling backwards at this location. This engine does not cause the spike when facing the other way on the track, going forwards or backwards.

So this issue is VERY particular...

I have seen engines where the wiring is very tight from the factory. Possibly an issue here? Conditions are just right to cause some wire to short?

hold the engine and turn each truck gently, checking for free travel. Possibly one might show some sign of an issue here?

Otherwise, if it was mine, I would go inside and check for shorting. 8 amps is big. The engine doesn't stop so I'm thinking the short is on or to the frame. I fear continued running might cause worse damage and get expensive.

and I agree with Rich here! Thank you for the extra clarity.

Two ideas.

1) There is a partial short in a truck that only now reared its head since you changed directions.  Inspect the trucks and wires leading to and fro.  Could be a pinched wire too that turning that direction causes it to put tension to.

2) that loco (being somewhat heavier) going in that direction puts enough force on a particular piece of track causing a stray wire in the ballast to short.  Maybe from a stranded piece of wire when cutting or stripping the insulation.  Inspect the track and ballast between the rails closely.

Quite a puzzle, but those are my random ideas.

Thanks for providing such detailed info about the problem!

Here's my 2 cents...

It looks like the curve is very sharp for an engine of that size.  Are the blind wheels on that engine made of metal? If so, could one of them be touching the center rail and causing a short?  Or could the pickup roller (or bracket) be touching one of the outside rails? Could there be a slight twist in the track that is causing that to happen?

Please post the resolution when you find it.

It is NOT your trackwork! Is this the sharpest curve this engine negotiates on your layout? Your symptoms are screaming "temporary internal wiring short" to me. The fact that it does this in only one direction is tell-tail. I think as the motors turn the wires to them tighten up and something touches that should not touch. Figuring out exactly where that touch point is is the hard part. You can pull the shell and examine all the wiring around the motors for burn marks. Look very closely where the wires attach/go through the motor block. That's the most likely point. You can also try loosening the wires a bit to given them more play. Try running the engine with the shell off in a darkened room. Slowly run the engine into the curve and watch for sparks. Kill the power as soon as that happens!

Chris

LVHR

Gotta' go with Chris here, it's not the track, it's the engine.

@lehighline posted:

It is NOT your trackwork! Is this the sharpest curve this engine negotiates on your layout? Your symptoms are screaming "temporary internal wiring short" to me. The fact that it does this in only one direction is tell-tail. I think as the motors turn the wires to them tighten up and something touches that should not touch. Figuring out exactly where that touch point is is the hard part. You can pull the shell and examine all the wiring around the motors for burn marks. Look very closely where the wires attach/go through the motor block. That's the most likely point. You can also try loosening the wires a bit to given them more play. Try running the engine with the shell off in a darkened room. Slowly run the engine into the curve and watch for sparks. Kill the power as soon as that happens!

Chris

LVHR

Thanks to everyone for the replies so far!

I think you're  probably onto something here. It might be an internal wiring short that only happens when the engine's trucks are turning to the left.

As for the curve radius, all my curves are O-36, so this one isn't any tighter than any other curve on the layout. BUT, this particular curve is also the end of a slope, and although the transition  is gentle, the angles involved might be tilting the trucks to a point where contact is made between wires somewhere on the inside of the engine body.

I will take the shell off and look for obvious issues. I'll then do a slow test run to see what happens.

Based on the symptoms, are there any particular wires and/or components that would likely be causing this that I should pay attention to? For example, the pickups to the board. Or the board to the motors. Or other electrical wires like the couplers or lights?

Thanks!

The first wires to look at are the ones off the pickup rollers, as they are moving a lot of the time.

Problem solved! 😁

The issue was, indeed, the internal wiring. The wires leading from the board to the rear motor were getting pinched between the rear pickup roller wire and the volume & smoke control metal support frame.

The picture above shows the damage to the wire. The insulation has been worn off, exposing the wire underneath which then makes contact with the metal engine body when the truck is turned hard to the left. The video shows how the wire gets pinched.

I guess the angles involved in this particular curve (the elevation change combined with the curve itself) led to the issue. Other turns might have contributed  to damaging the insulation, but only this curve was causing actual contact with the bare wire.

To solve the problem, I wrapped electrical tape around the damaged wire and also around the metal post at the point it was rubbing against. I also zip-tied the affected wires to other wires that were slightly above them, to help hold the damaged wire away from this pinch-point.

Thanks again to everyone who offered their input! You definitely  helped me solve this problem a lot faster!

Great!