Just Dumb and Non-Observant

[D&J RailRoad]

I'm still laying track on the new D&J Railroad. Cork is laid out about a mile ahead of the track. Each section of work is completed and barbell plates are laid on top to hold things down till the caulk/glue dries.
I hooked up the Digitrax Command Station to run a locomotive a few days ago and noted that it seemed to be running kind of sluggish. I had a string of freight coupled to it and thought maybe its just the weight of the train. Ran the loco deadhead and it still seemed kinda slow. Checked power and it was were it should have been. Went through the issue of the reset button that I noted in another thread here.
Last night, had a friend over to work on the layout. Running the train again checking track flaws when it suddenly occured to me that the barbell plates were still laying on the track about a mile further down the line from were I was running the loco. I went over and picked them up off the track and whoaaaaaa, the train took off, all better now.

 

[Secondhandmodeler]

I did the same thing when I built my first layout. I had been using some full, quart size paint cans to keep a section of new track in place. I tried to run a train and couldn't for the life of me figure out why it wouldn't run. Then I realized the paint can was metal and was creating a short between the rails!

At least it wasn't your locomotive.

 

[RW&C]

And at least you didn't blow up the Digitrax! I smoked a mosfet in my NCE that way... still gotta fix that.

 

[Selector]

This behaviour suggests to me that you don't have enough voltage showing up at the rails everywhere. The short detection circuits in all DCC systems rely on a heavy Signal/Noise ratio, and they don't like voltage drops anywhere more than about 0.6 volts. Once you get above that, your DCC base unit will not likely detect a short, but if your decodered locomotive is in a gapped shorted section, and one of its components is doing what the barbell had been doing [i.e., causing a dead short], you would find all the provisional amperage rating for your power supply coursing through the decoder. Phzzzt....sniff, sniff. Cough, cough.

The barbell was causing a dead short, so why didn't your base unit go beep and shut down the power to the rails? It is an important question. I think you might want to check your power supply to the rails, maybe a cold solder at a feeder, or maybe you need at least one more feeder pair near where the barbell was causing the non-detected short.

 

[D&J RailRoad]

There are about 12 flextrack sections between the last soldered feeder and where the plate was laying on the rails. The conduit between the soldered track and the plates was the track joiners.

 

[Selector]

Yikes!!! Sorry, don't mean to be melodramatic... The other extreme is one pair of feeders soldered to every single length of flex...which I feel strongly is overkill, although you can't argue it isn't a 100% insurance against voltage problems.

Yours is the most extreme case I have heard in the other direction. Ideally, about 10' per pair of feeders is the norm, and many use one pair of soldered feeders to the joiners holding any two lengths together, so about 6.5'. Much past 15 feet and your system will have problems of the kind you now understand more completely. You need another two pairs of feeders spread evenly over that length. You'll see a big difference.

Incidentally, when your signal-to-noise ratio is acceptable, you'll be able to do what we term 'the quarter test' at any spot on your rails. Drop a clean quarter on the two rails and look for your powered up system to indicate a short. Doesn't get better than that. Yours failed a barbell test.

 

[Selector]

Oh, and another thing - the joiners appear to be affording your rails two things: mechanical alignment and electrical continuity. Yes to the former, nyet to the latter. Those of us who have had a layout for a couple of months or more eventually learn that the joiners invite electrical problems long before they get bent or damaged by mishandling. Their metal composition is different from the other metals nearby, so their is some electronic activity where metals oxidize. Eventually the joiners will have to be slid back and forth to scrape away a clean purchase. That gets old in a hurry. So, what we do, most of us eventually, is learn how to solder and do most of the joiners. The solder keeps the electrons flowing, and if done at the joiners, also strengthens sloppy joints.

My own practice is to solder a pair of feeders to every second joiner pair. It can be represented thusly:

========X=========O========X========O=====

The X is a soldered pair, and the O is a simply placed joiner for mechanical alignment. You can readily see that soldering every other joiner provides the maximum voltage for the length of each flex track component in either direction.

 

[D&J RailRoad]

I just haven't gotten to soldering the feeders that far down the track. Remember, this is still under construction.
From past experience, I don't want to rely on a pinch connection for electrical connection. Every track will have a feeder from the power bus soldered to it. The track joiners will be only for the purpose of keeping the track aligned.
Considering how the loco was performing that far from the dead short (plate) I think the track was conducting rather poorly for the 40 some feet of track joiner only, electrical connection.
As far as soldering the track joiners, that will create a problem with track expansion and contraction. I chased that little exercise down about 10 years ago and it turns out the track will expand about 1/10" with a 20 degree change in room temperature. Soldered track joiners will cause your track to buckle rather than slide along the ties. Alternating the track so the sliding rail is on one side of the track then the other with each piece of track will optimize and accommodate the track expansion and contraction.
I'm sure the quarter test will present the expected results of a well connected railroad.
Went through all this with the previous D&J Railroad.

 

[Selector]

Ken, it is true that a major swing in temperature can affect your track, especially when it has not been well ballasted to keep it put. Humidity in timber benches is about three times as bad. So, while some people solder every joiner, I try to leave a pair free to slide every 20 feet or so, and I place my roadbed on acrylic latex caulk so that it can decouple a bit from the benchwork under it to spare it from too much strain. I also count on gaps that I must leave between sections that are meant to come apart, such as across the joints between modules.

I hadn't appreciated that you are still in the 'development' stage with your feeders, so it sounds like you have it all figured out.

 

[Cjcrescent]

I'm still laying track on the new D&J Railroad. Cork is laid out about a mile ahead of the track. Each section of work is completed and barbell plates are laid on top to hold things down till the caulk/glue dries.
...
Last night, had a friend over to work on the layout. Running the train again checking track flaws when it suddenly occured to me that the barbell plates were still laying on the track about a mile further down the line from were I was running the loco. I went over and picked them up off the track and whoaaaaaa, the train took off, all better now.

I've done something as dumb as this recently. I had some of the local NMRA judges over for judging on my Civil and Electrical on my layout, and the layout just quit working all of a sudden, and no matter what I did, it would not work at all. It kept showing short. I took all the equipment off, checked all electrical connections, then discovered that I had placed a Sprite can across a couple of rails! Talk about embarrassing!

But after it was found, I was awarded my Electrical and Civil, in spite, or should I say in sprite of this!

I also got a special award for this, but the judges didn't want to sign it, as it would identify them to the world, as they couldn't find the short either!

 

[bnsf971]

Yours failed a barbell test.

Would that be a "dumbell test?"



going back to my basement now...

 

[Selector]

If I had done it, surely, but our friend was merely absent-minded.

 

[D&J RailRoad]

That's an award you would hang on the wall at the back of a closet.

 

[Cjcrescent]

That's an award you would hang on the wall at the back of a closet.

Right now it's displayed horizontally on a shelf of to do projects!

 

[bnsf971]

Right now it's displayed horizontally on a shelf of to do projects!

I suppose you could also display it vertically in a circular storage bin.

 

[Cjcrescent]

Nah. I'm not insulted or anything! I actually got a kick outta it. It's really I guess you could say, its from our local 100% NMRA club, The Wrecking Crew. We have several MMR's, Past Regional Presidents, NMRA National Directors, other Past Regional Officers and Directors, and a huge bunch of qualified NMRA judges. (We have a very active NMRA Division here).

We all have a big, (sick), sense of humor. We tell everyone that if you're gonna make a mistake, make it a BIG one, as we'll never let you live it down, and trust me, I have made some doozies over the years! At least once each year, we give out what we call our Dubious Awards, which are awarded for any mistake made over the year. Needless to say, I've picked up several during my membership of over 25 years. This is merely the latest.