DCC steam engine stalls on S curve


M

Mister Bill

Member
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
 
What radius curve do you have at those points? It is possible that the center driver is being shifted sideways until it either is shorting or breaking contact. You might want to set up a test track and see if pressing sideways on the center driver has the same effect. Not sure what you can do to correct that problem, especially if the drivers are spring-loaded downward. On my non-sprung driver steam locos, I ship the center drivers up and the end drivers down by .005" (the center drivers are all blind).
 
It's probable that when the engine enters the second part of the S curve, it is lifting the wheels of the tender off the rails, breaking contact.
 
Without any imagery its kind of hard to help diagnose the problem.
Do you have any straight track between the two curves?
 
Ken, no, I had space limitations and there is maybe one inch of straight until the unit enters the other half of the S. 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.

Also, my BLI 2-10-2 takes the S curve, as well as all of my diesels, with no problem.
 
Hi. If you're saying it does the same thing on both S sections, then I believe the radii of the two S curves are lifting a live-pickup tender truck off the rail, as Ken is hinting at. If this turns out to be correct you'll either have to mothball, sell the engine, live with the stallouts, or figure out a way to redesign the track in the 2 areas..Opposing curves require a tangent between them the length of your longest piece of equipment, to prevent opposing couplers or drawbar from maxing out, side to side..M
 
S sections are the cause of many problems on model railroad layouts. Follow MarkinLA's advise and do a redesign if possible.

Thanks.

Greg
 
What kind of connection is there between the engine and the tender? It sounds like in that direction of curve something loses contact. look also for a truck hitting a frame or the pilot wheels/trailing truck touching something just for an instant. Get lights on the curve and run the train to where is stalls then check the engine to see what is touching or not touching. Then move it a few inches and see if there is anything different. Look at every wheel, every truck, every wire.
 
In relation to dave above, I'll add: When it stalls, is it a lack of current (an 'open') ? Or, does the NCE screen go dark and shut down ? If it does shut down it's a short, and throttle's circuit breaker will have opened to protect it.
 
Mister Bill said:
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.
Click to expand...
Tiny dip in the track? Check for totally level railheads. I'm guessing the 6 coupled locomotive doesn't have any blind drivers and are of larger diameter while the 10 couple does have blind drivers of smaller diameter.

But all the things suggested means there aren't enough power pick ups. Lifting one wheel or even one whole (loco or tender) should break the electrical contact and stall the loco.

Check the rocking ability of the tender trucks both forward and back as well as side to side. As someone else has already suggested check the loco pilot and trailing truck to see if they are shorting on something (I had a 4-8-4 that liked to do this).
 
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