"Stuttering" locomotive


mgj21932
 

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


John Myers
 

Is it all your locomotives or just the one?   


On Sat, Jan 9, 2021, 12:53 PM mgj21932 via groups.io <mgj21932=yahoo.com@groups.io> 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


wirefordcc
 

 

 

From: w4dccqa@groups.io <w4dccqa@groups.io> On Behalf Of mgj21932 via groups.io
Sent: Saturday, January 09, 2021 3:53 PM
To: w4dccqa@groups.io
Subject: [w4dccqa] "Stuttering" locomotive

 

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


D B
 

John Myers,

What  great question!  Test loco was an MTH 2-8-2 Mikado.  Ran BLI 2-6-6-4 N&W “A” on same tracks.  No problem!  

Tried MTH Mikado without DCC-effects (no lights, no smoke, no sound), just running loco.  Ran over the AR track segments without problem!  But same stuttering issue returned (now on other AR segment) when lights/smoke/sound were on.  I will do more sensitivity assessment, putting “on” these features one-by-one to see whether any single one is cause.  

Thanks for your suggestion.  Sounds like I have a decoder issue I’ll need to have MTH take a look at.

Now even more track issues to address with the big “A” loco — much more sensitive to any track irregularities due to size.  Running 22” min. radius turns but encountering issues with “standard” Atlas turn-outs in particular.

Bill D
N&W Steam Only


wirefordcc
 

Hi Bill,

It sounds like your circuit breaker is turning off, waiting for the fault to clear, turns the power back on again briefly, finds the fault again and repeats the cycle by turning the power off again.  If you have your auto reverse device in series with the circuit breaker, it sounds like they are competing with one another.

Allan Gartner
Wiring for DCC


Don Vollrath
 

Bill D, look for poor electrical connections of the power pickups in the locos. Particularly if there are vertical irregularities in the rails. Run the locos at a very slow speed to see where/if the wheels lift up. Use a test light clipped directly to the rails or rail feeders away from the troubled areas to verify that the rails from the AR controller are staying powered. Look for poor connections moving at rail joiners or broken solder joints to rail feeders.

22 inch radius is rather tight for large locos. Put small test lights at the AR section gaps to observe any power loss or polarity shifts when the stuttering occurs. Watch the loco headlight. If you see this happening look for shorts or opens occurring on the track or inside the loco chassis as the driver wheels swivel.

DonV


D B
 

Allan,
That’s what I thought. But problem wasn’t happening on other AR wired segment.

John Myer asked whether problem occurred with all my locos. Turned out that problem is loco-specific and not related to my CB/AR wiring.

So now I need to figure out what the issue is with the loco. Don Vollrath has made some great suggestions which I will follow up on.

Bill D
N&W Steam Only

On Jan 10, 2021, at 9:38 AM, Don Vollrath <donevol43@hotmail.com> wrote:

Bill D, look for poor electrical connections of the power pickups in the locos. Particularly if there are vertical irregularities in the rails. Run the locos at a very slow speed to see where/if the wheels lift up. Use a test light clipped directly to the rails or rail feeders away from the troubled areas to verify that the rails from the AR controller are staying powered. Look for poor connections moving at rail joiners or broken solder joints to rail feeders.

22 inch radius is rather tight for large locos. Put small test lights at the AR section gaps to observe any power loss or polarity shifts when the stuttering occurs. Watch the loco headlight. If you see this happening look for shorts or opens occurring on the track or inside the loco chassis as the driver wheels swivel.

DonV


D B
 

Thanks Don.

Ironically the problem doesn’t occur with my large (2-6-6-4 N&W A) loco; that just keeps derailing ! LOL. The stuttering occurs with the 2-8-2 Mikado and that runs fine on 22” radius curves.

Issues are undoubtedly related to a short within the loco (pick-up or loose wire connection) causing the CB to cycle. I will investigate as you suggest but I think this one is on to the local HO Hospital where they do a very good job.

The bigger concern is what to do about keeping the big guy on the tracks and able to negotiate the turn outs. I fear I am going to be very disappointed.

Bill D
N&W Steam Only

On Jan 10, 2021, at 9:53 AM, D B via groups.io <1932mgj2=gmail.com@groups.io> wrote:

Allan,
That’s what I thought. But problem wasn’t happening on other AR wired segment.

John Myer asked whether problem occurred with all my locos. Turned out that problem is loco-specific and not related to my CB/AR wiring.

So now I need to figure out what the issue is with the loco. Don Vollrath has made some great suggestions which I will follow up on.

Bill D
N&W Steam Only
On Jan 10, 2021, at 9:38 AM, Don Vollrath <donevol43@hotmail.com> wrote:

Bill D, look for poor electrical connections of the power pickups in the locos. Particularly if there are vertical irregularities in the rails. Run the locos at a very slow speed to see where/if the wheels lift up. Use a test light clipped directly to the rails or rail feeders away from the troubled areas to verify that the rails from the AR controller are staying powered. Look for poor connections moving at rail joiners or broken solder joints to rail feeders.

22 inch radius is rather tight for large locos. Put small test lights at the AR section gaps to observe any power loss or polarity shifts when the stuttering occurs. Watch the loco headlight. If you see this happening look for shorts or opens occurring on the track or inside the loco chassis as the driver wheels swivel.

DonV





Jim Betz
 

Bill,
  MTH locos are not "100% DCC Compatible" - they are "DCC Tolerant".
Said another way - they are designed for the MTH system and don't
fully support DCC (which is different).  For this reason I tell guys
"don't use MTH on DCC unless you are willing to accept some
problems".  Usually those problems are in :functions that don't
work/don't work the same" and do not affect running ability - so make
certain you tell MTH what system you are running their loco on and
the details of the problem.  I suggest you take the time to diagnose
if the problem is related to one particular feature/function - by turning
stuff like lights/no lights on and off one at a time and then in combo
until you can fully describe the problem to MTH.  
  Do not be surprised if the answer you get is "run it on MTH and it
will be fine".  
  Your other locos - non-MTH - will probably not run correctly on an
MTH system.  MTH has designed their system (and decoders) to
"encourage the user to buy their system and their locos only".
  I can not explain why it ran fine for a while and is not acting up.
Perhaps you weren't always using the same loco and this one is
new to you?
                                                                                                      - Jim


Puckdropper
 

Auto reversers work by sensing current draw over a certain level and flipping the polarity in an attempt to fix that. With all your lights on, plus sound etc, you may be drawing more than the trip level of the device.

I'd suggest changing to an auto reverser (Ar-1, PSX-AR etc) meant for track use and using the hex juicer for its intended purpose.

Puckdropper


D B
 

FYI, in case anyone else experiences this phenomenon, further investigation (turning certain DCC functions on and off to isolate the culprit) revealed that it was the smoke function which was triggering the CB to trip and reset. Not sure whether there might be a short somewhere in the wiring for the smoke unit and/or fan, or whether the smoke/fan was drawing too much current and tripping the CB. Either way, until I can get it addressed professionally, I can still run the loco with most DCC functions. One of the diagnostic challenges was that the problem did not appear to fully manifest itself until the smoke unit fully heated up, which took some amount of time.

Thanks for the assistance.

Bill D
N&W Steam Only


Glenn
 

Check your rail joints. Soldered joints often fail, but ......

Insulated joints can become dirty from gunk trapped in them. If you ever used a track cleaner block or sand paper to clean the rails, metal filings can be trapped in the joint. Spray cleaners that improve connectivity can glue these in the joint.

Like metal joiners the simple vibration of rolling stock can cause intermittent connectivity and trip the circuit breaker.

This type of connectivity will not be detected with a bulb, it's off time is too short to be detected by the eye. A multimeter may be better, since a short will show as a 0 voltage. It will more likely show as an erratic dial movement.

I would recommend sealing these joints with epoxy or clear nail polish. This will fill in any gaps and prevent junk accumulating. Sand the rails afterward.

Glenn



D B
 

Thanks Glenn, 
But issue appears to be related to smoke unit drawing too much power (or heating up and causing internal issues within the loco). I appreciate you suggestions re: track-rail connection integrity and will try to implement them.  
Bill D
N&W Steam Only


On Jan 11, 2021, at 8:11 PM, Glenn <ghazel@...> wrote:


Check your rail joints. Soldered joints often fail, but ......

Insulated joints can become dirty from gunk trapped in them. If you ever used a track cleaner block or sand paper to clean the rails, metal filings can be trapped in the joint. Spray cleaners that improve connectivity can glue these in the joint.

Like metal joiners the simple vibration of rolling stock can cause intermittent connectivity and trip the circuit breaker.

This type of connectivity will not be detected with a bulb, it's off time is too short to be detected by the eye. A multimeter may be better, since a short will show as a 0 voltage. It will more likely show as an erratic dial movement.

I would recommend sealing these joints with epoxy or clear nail polish. This will fill in any gaps and prevent junk accumulating. Sand the rails afterward.

Glenn