Re: "Stuttering" locomotive

John Myers

Is it all your locomotives or just the one?   

On Sat, Jan 9, 2021, 12:53 PM mgj21932 via <> wrote:
I have a DCC layout, using NCE PowerCab.  Basic figure-8 layout with two reversing segments.  Tam Valley circuit breaker in series with Tam Valley frog juicers as AR circuits.  Finished wiring track and began testing with MTH 2-8-2 light Mikado steam loco to identify track irregularities which require attention and turn-outs which require adjustment or tuning.   

First of all, there were no "electrical" issues.  Loco ran well except for occasional derailments at various points -- which is what the testing was designed to identify.  

All was going well -- finding a number of places where the track needed attention.  The AR switches worked perfectly; indeed, initially both reversing segments appeared to work perfectly.   

Inexplicably one of those segments is now acting up.  The loco works fine on entering into the segment, but about 9"-12" in, the loco starts "stuttering" -- moves forward a fraction of an inch for maybe 1/2 second; then stops; then moves forward again a fraction of an inch for 1/2 sec; stops; starts . . .   You get the idea.

I checked continuity between track segments with 1.5v battery light-bulb tester: good from both ends; as were continuity of connections between track feeders and tracks; connection between feeders and track bus; connections between track bus and TV AR switch.  All appear to be solid.  AR switch is working properly. 

Checked for continuity between parallel tracks:  none.   Also checked for isolation gaps at both ends.  Both show no continuity across the plastic connector-insulated gap.

At a loss.  Thought perhaps feeders might be cross-wired.  Removed "middle" track segment between two feeder connections located toward opposite ends of the AR segment, and ran loco onto the no- longer-continuous AR-wired segment from both ends.  Loco runs fine on the main line and runs onto the AR segment's two ends, about 9" or so, before starting to stutter, stop and start as described.

When this stuttering is occurring the Tam Valley AR switch's LED lights are flashing with each "stutter", and the LEDs on the circuit breaker are flashing like the power is being turned on and off.  Something must be triggering those, and as the power is cut and restored, then cut again (or the "polarity" is switched back and forth by the AR switch), the loco stutters forward, stops, and restarts, etc.  But I cannot figure out what is causing the problem.  Particularly mystifying is why the stuttering phenomenon seems to be triggered at 9"-12" into the segment, rather than right at the "gap" after the train has run onto the segment. 

Is it possible I am getting cross-track interference (electric continuity between track rails) from the silicon caulk I used to fix the track to the cork roadbed?  Even though my light-bulb continuity tester does not register any such continuity?   That's the only thing I can think of because I did attach some "loose" track to cork roadbed with silicon caulk after the loco had run on the track segment without any electrical problem, but derailments of the front truck of the tester loco seemed to be caused by inadequately anchored track in a couple of places, or slight mismatch of track rail ends at connection points.  Stuttering started some days later when I got back around to testing this segment for track issues.  No track issues but huge electrical issue.  Yet diagnostic tool does not show a problem. 

Bill D
N&W Steam Only

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