# DCC steam engine stalls on S curve



## Mister Bill (Jan 30, 2014)

I have a Broadway Limited 4-6-2 that stalls in the same place every time on my layout when every other engine runs through the area just fine.

My layout is a double dogbone with two identical S curves of code 100 flelxtrack. There are no joints where the engine fails. It just loses power and shuts off. If I nudge it a ¼”, it starts again and makes the lap around the rest of the layout just fine and stops dead the next time around. If I change directions, it runs through the problem area and stalls on the mirror image of the flelxtrack dog bone on the other side. With a piece of flex track, it cannot be the track work. The track is super clean. Granted, there is very little straight away in the middle of the S curve.

Can anyone suggest a cause? I don’t know if it is a decoder problem, track problem, or a manufacturing defect.

Bill


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## CTValleyRR (Jul 26, 2014)

It absolutely can be the trackwork. In fact, if you know that there is no crud on the track that is causing a stall, then it MUST be the trackwork.

An S curve is one of those "avoid if possible" track situations. Especially with steamers, it is possible that the wheels are binding in the S, either jamming in the gauge because the wheels are still trying to go one direction when the track starts to go the other way, or the wheels can't follow the track undulation and are riding up over the rails just enough to break contact with the rails, causing a stall. In either case, the nudge frees it to keep running.

You may be able to see what is happening by getting your eyes and a bright light right at track level. I'm afraid that the only solution is going to be realigning the track in those S curves.


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## Mister Bill (Jan 30, 2014)

Thanks. 

Ironically, I have double track, and the engine stalls on the 28" radius portion but passes through the same 24" radius S curve. Same Atlas flex track, unballasted.


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## CTValleyRR (Jul 26, 2014)

Mister Bill said:


> Thanks.
> 
> Ironically, I have double track, and the engine stalls on the 28" radius portion but passes through the same 24" radius S curve. Same Atlas flex track, unballasted.


The "radius" that you're quoting probably isn't. While the flex track itself may be curved to that radius, the S shape means that some wheels are rounding a 28" curve in one direction while the rest of the wheels are doing something else. Unless that "something else" is going straight, then the wheels aren't actually experiencing a 28" radius.


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## DonR (Oct 18, 2012)

When a loco stops and lights go off...it has lost
contact with track power.

You can use your multimeter set to AC volts and
run the probes along the rails at the point where
the loco stops. If you don't see a loss of power the
problem is loss of power pick up in the loco and/or tender 
wheels.

I suspect that the twisting of the S curve could be
causing a power pick up wiper to loose contact
with the back of one or more wheels, thus losing
power. 

I don't know your loco, but some transfer power from
tender to loco using a metal draw bar. This could
be a problem in an S curve.

Don


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## Lemonhawk (Sep 24, 2013)

I push a map pin in next to the track the is experiencing a problem. Makes it easier to then observe what actually happens at that point. You might try add some more weight to where the power is picked up (tender or engine) just to see if that makes a difference. If the drawbar between the tender and engine also conveys power, then I would be suspicious that connection is being lost. Also, after it stops look closely as you nudge it to see if there are any sparks generated near the wheel pickups.


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## MichaelE (Mar 7, 2018)

Do all wheels have a pickup wiper? If not, then I think the s-curve is your problem in this one spot.


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## Magic (Jan 28, 2014)

I'd check and make sure your track is level side to side.
A small line level works good for this.

Magic


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## gregc (Apr 25, 2015)

do you know from which (or both) rails power is lost? 

with the engine stalled, i take a wire with clip leads and connect it between the rail and wheels to determine which side lost connectivity. I think the tender picks up power from the left rail and the engine from the right rail.

it may be the drawbar connection with the engine. try bridging the left rail with the drawbar to see if it's the wheels that have the problem and if not the drawbar pin on the engine

once you know where the bad connection is, you can try to figure out why.


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## Mister Bill (Jan 30, 2014)

Thanks. 

All good information.


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## J.Albert1949 (Feb 3, 2018)

Since all the OP's other engines run well enough through this location, I'm thinking it's got something to do with the electrical pickups on the engine.

Or perhaps a unique "loose connection" that occurs only when the locomotive/tender move through the S-curve...?


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## CTValleyRR (Jul 26, 2014)

J.Albert1949 said:


> Since all the OP's other engines run well enough through this location, I'm thinking it's got something to do with the electrical pickups on the engine.
> 
> Or perhaps a unique "loose connection" that occurs only when the locomotive/tender move through the S-curve...?


Yes -- something in the track geometry (the S curve) is either lifting the power pickup wheels off of the track, or torquing something so that the wipers lose contact.

Since we don't know the type and axle configuration of the OP's other locos, we don't know whether the S curve would bother them or not.

And since, as the OP says, the S curves are formed from a single piece of flex track, I think we can rule out loose connections.


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## Djsfantasi (Mar 19, 2019)

Just an aside. If an S curve does NOT have a straight section greater than the length of your longest rolling stock between the opposing curves, you WILL have issues. It’s a matter of proper design. Just saying!


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