Track loss exaggeration

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Bread&steel

Member


Like everyone else who runs DCC I have a main bus. I used number 14 bare copper wire. I ran my bus wire first before connecting the feeders. It occurred to me to test the " track lose theory " so I connected the feeders from my track to my DCC unit. I had no bus connections at all. I ran my locomotive, starting at the point where the feeders were connected to my DCC unit and I ran my locomotive at low speed around my layout to see how far it would get before I saw any problems. I blew the horn, I rang the bell and it just went on and on and on until it reached the entrance of my foundry. That was almost half way around my layout and not one hint of trouble. Since I've already ran my bus I decided to install feeders every ten feet, just to make sure everything runs fine. So I have seen for myself that on a small layout, no bus would be necessary. On a large layout it would be a good idea but with just a few feeders :D
 
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ThoroughBreed

Dcc~detail~diesel freak
Hello all.
I have a small 8x11 double track mainline with broad curves (not much straight away lol), and have it on a 12 gauge bus, with feeders every 3 ft. I too believe its a little overkill for such a small layout, but cant never be to careful. I'm using a MRC Prodigy Advance2 3.5 amp for my DCC.
I'm working on an upper level for it, but didnt plan for it in the beginning, so its improvise as I go. I'm trying to keep my grade below 2, so its a long winding path to the upper level, almost 2 full helixes. The upper level is nothing more than storage tracks, and engine facilities, so only partially viewable when finished. But it will be a circle with a long leg, and will prob need a booster for the leg, as most of the engines in the storage area have sound. LOL:cool:
 
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SpaceMouse

Fun Lover
It may be an exaggeration, but I tend to think that time, a few bumps and jiggles, and oxidation tend to degrade a layout's electrical system. Your experience may vary. It's just not that much more work to be sure.
 
I have a 24'x24' layout and I have done many smaller ones in the past. I dont know much about electrical things but seem to get it to work. That said I can say from past experience a buss line is not that much trouble and adding some extra feeders before scenery work is completed would certainly be easier. I agree with Chip as things age and solder joints break down and wheels and track get dirty and engines age good power may be an issue.
 

RexHea

RAIL BENDER
Larry, I agree with you that there is a lot of overkill with all the busing and feeders. All anyone has to do is the electrical math. However, another way to look at it is the more feeders the less problems with bad track connections, particularly those involving turnouts. It's good to have power feed on two sides of a connection just because of this.

Example I had a Walthers Shinohara TO that diverted to a long dead-end spur. The TO has little tack welded jumpers that are suppose to give you power all the way through. Well, one broke and my spur was dead because I didn't have additional power on that long spur. I usually place a feeder about every 6-9 feet of mainline and 1 on each spur or yard rung because of this. I also solder all my track joiners.
 

modelbob

Administrator
... All anyone has to do is the electrical math....
Well yes, but here's the catch. While the rails are large (often as big or even bigger than the feeder wires) they aren't the problem. As you suggest, they carry the current quite well, and you can have long runs without difficulty.

The problem is the rail joiners, and the very tiny contact points they have. Add in oxidation, and possible loose contacts, and you end up with what's essentially a resistor at every connection.

The best solution to that is, as you suggest, feeders every few feet. I suggest that folks not solder the joints together, as that will simply result in your rails being stessed and kinked as they expand and contract during hot and cold weather. The joints allow for that expansion, and it's best to allow them to move.
 

Bread&steel

Member
Hi Rex. I also solder all my joiners and I have had dead Shinohara TOs at times. One was to a dead end spur as well ! The loco would enter the TO and go dead. Same bad jumpers; two of them ! But I think that people like the staff of Model Railroader should be more to the point and should stop giving modeler the impression that NS track is like a GD resistor ! It's not that bad ! You should teach on those DVD they put out because you get to the crux of the matter which is that bus helps prevent problems with bad joints and broken TOs and just helps your RR run better.
 

Bread&steel

Member
Modelbob ! This should be something the Kalmbach people should do. Run tests ! Soldered and unsoldered... Change the room temp... Measure the expansion and contraction. Measure the track resistance. Modeler always argue on this point and I think it's time science put an end to the debate ....what do you all think?
 

modelbob

Administrator
Modelbob ! This should be something the Kalmbach people should do. Run tests ! Soldered and unsoldered... Change the room temp... Measure the expansion and contraction. Measure the track resistance. Modeler always argue on this point and I think it's time science put an end to the debate ....what do you all think?
It would be an interesting experiment...

The expansion is quite simple to determine, it's called the "coefficient of expansion". You look up the type of metal you're using, and there will be a number that tells you how much it expands for each degree change in temperature. It can be a big factor, depending on where you layout is. Mine is in an unheated area of the house, and the track definitely moves during the changes in temperature. I used to weld my rail joints, and it caused problems with the track pulling and kinking etc.

However, I think the two major factors are simple, and in fact would be easy to test, if anyone is up to the challenge.

The first is the very small contact area that joint bars have with the rail.

Second is oxidation, and while it's less on nickel silver, it's definitely a factor.

So... Want to do a test? Here's what I suggest for the HO scale version of Mythbusters.

Lay two sections of track. One with flextrack, using 3 foot lengths, and if you want to go longer, solder the joints together.

Then lay a section of snaptrack, using the 9 inch sections.

Make both tracks the same length, maybe 6 feet long.

Take an ohmeter, and check the resistance of both. See if there's any difference. Then let the track sit for a while and check it again.

Simple enough...
 
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I dont recommend soldering rail joints they are needed for expansion and contraction. No time to get into the problems I have had with that. I do suggest doing a jump around wire on the sections that dont have feeders.
 

Bread&steel

Member
I agree that if you don't use a bus then you should use jumpers across unsoldered rail joints.

Modelbob. Maybe we can convince Kalmbach to do this test. They can go a bit farther and test the track from different manufacturers and let us all know which one is the best performer
 
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RexHea

RAIL BENDER
I believe the track resistances and expansions would be excellent and worthy lab tests for Modelrailroader. But because of so many variables, both dependant and independent, it would have to be a strictly supervised test under lab conditions to prove anything. The parts, temperature, humidity, ambient air quality, benchwork, must all be the same. Also, the amount of stress on these parts must be the same in the tests (curves and straight sections). I would venture a guess that the reason they haven't already done this is because of the environmental and structural differences in every layout. However, it would be grand to have a benchmark.

Included in the tests, should be ballasted vs. unballasted track for track expansion/movement (Does the ballasted track have less movement? Does it create more stress on the joints during expansion causing worse alignment?) Just how much expansion actually takes place. I have read on Trains.com where a guy did an expansion test on N/S rail in lab conditions and the expansion was negligible. (Personally, I believe rail always gets the blame for what the benchwork is causing.)

Where many have a problem with expansion or track movement, I have been lucky in not experiencing this. I have ballasted and unballasted, soldered joints, and joints that are waiting to be soldered, in a garage that the temperature may vary from 72 during work/play sessions to as low as 50 or as high as 80 overnight.

One oversight that many neglect to include during debates of voltage loss is the command modules/booster ability to supply a constant voltage to the varying current loads. There is indeed, a resistance in tracks, joiners, t.o.'s., and etc..., but if the command module is capable of supplying the amount of current for the load, it should maintain a constant and regulated voltage to the load. Once the current load goes beyond this capability, the supply voltage will drop. Many, when buying a command module, will add up the max. current loads of the locos, but do not include the load of the track parts. This could be minimal or be enough to have an effect when running the max number of locos and enough to overload the capabilities of the supply module, i.e. drop in voltage.

When setting up a Digitrax and other modules with a trim for track voltage, you adjust the voltage on the rails by clearing everything off the track (the meter completes the series circuit). This allows you to set the voltage to the desired value and compensate for the "series" rail resistance. (Look at the track as a big series resistor.) After placing everything back on the track, they are in parallel with the supply voltage and each parallel leg has the same voltage, but varying current values.
Example, my layout: When I measure voltage at the command station and compare it to the far end of my layout measurement, that is about 80 feet away, it is the same. If I were to measure the voltage in branchlines, it would be the same. However, current values would be different depending on what was on the branch. Current supply capabilities is the key word...not voltage.
 
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Cjcrescent

Master Mechanic
...(Personally, I believe rail always gets the blame for what the benchwork is causing.)...
I definitely agree with you on this. Humidity and temperature exposures to the wood, from the first processing at the mill to ultimate placement in the layout, affects the wood to the greater extent than the metal rails. The reason tracks warp is not expansion/contraction of the rails, but what the rails are attached to, ie the wooden benchwork.

Unless your layout is built using some sort of metal for the benchwork, I believe 99% of track "kinking" of any kind is due to the wood and not the metal.
 

Bread&steel

Member
I have one long run of tangent ( straight ) track. I used great care in getting it straight. It's not straight anymore. It's an elevated stretch on pine with cork roadbed. Maybe it would still be straight if I used homasote...????
 

RexHea

RAIL BENDER
I would bet that if you're using a pine or fir board (1x4) that is supported only on the ends or few places, the board is warping. By adding more supports that it can be fastened to securely or run a strengthener board down the under-middle, you can eliminated much of this. To prove this to yourself, go to Lowes and buy 3 or 4 boards and let them freestand for a week or so. I'll guarantee you that 1 or 2 will warp. However, if you install these boards in a normal way of fastening and within a few days, they will stay straight.
Or: the cheap way is to look at the stack at Lowes. They came in to the store straight in the bundle, but after the bands were cut and the top and outside boards had freedom to move, many will warp depending on their moisture content and grain. (I have had some warp so bad that it could be used to build a V bottom boat hull as is:eek: :D .) Best thing to do is let our boards sit in the layout environment for a couple of weeks before using. This won't stop problems entirely caused by not securing the boards enough, but it will help considerably.

I have a long straight across an area that can't have any support under it because of a nearby duck-under. I used a hardwood board for this. Expensive, but no distortion.;) :)
 
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Bread&steel

Member
V bottom boards

I too have seen many warped 1X4's and know what you mean, Rex. I go through them looking for straight ones. I have, as you have suggested, reinforced all my questionable areas and maybe now everything will stabilize. But the main thought here, I believe to be correct. Track often gets the blame for poor bench work. :rolleyes:
 

Cjcrescent

Master Mechanic
...Best thing to do is let our boards sit in the layout environment for a couple of weeks before using...
Model Railroader magazine used to recommend 12-18 months for this. They may have changed this due to "modeler impatience". I know I could'nt sit there with a pile of lumber in my trainroom and watch it "dry" for 18 months:D:D:D:D:D:D:D:rolleyes:
 

modelbob

Administrator
12 to 18 months!?! Yeah, right, if you can forget about the hobby that long, you'll forget about forever...

I used the L girder system when I built my layout, which is, as the name implies, 2 boards bonded together in an L shape. This has worked amazingly well at minimizing warpage, since the board running the opposite direction resists bending by the other board.
 

Joe Daddy

C & SF, my obsession
Urban Legends

Wire size is one of those subjects I call an URBAN LEGEND in our hobby. In fact I have a list of about 10 or so URBAN LEGENDS listed on my blog.

There are so many variables and factors involved in dcc bus wiring that this very simple subject can get confusing and some really try to complicate it. Read some of the threads on the Yahoo DCC forums and you'll see what I mean.

For example, back to the original example stated in this thread, he ran his sound loco all over the place and never had any issues. You may be surprised to learn that sound locomotives draw very little current, all of mine less than .25 amps as measured by my RRampMeter. With that small current load, any voltage drop on the back side of your layout is probably not noticeable, unless you are measuring your speed with something like my Tunnel Speedometer. Let us face it, a locomotive can slow from 60 mph to 40 mph and many of us would never notice it without a speedometer.

Now, put a string of eight lighted passenger cars behind that same sound locomotive and you'll find your current requirement jumps to over 1 amp or more! Now, you are taxing the abilities of the DCC bus and speed / sound MIGHT be noticeably affected.

There are those who recommend 12 gauge for everything, some even suggest number 10! The issue is really one of workmanship, good solder joints everywhere, soldering track into sections of 6-10 feet and putting reasonable feeders on each section to an appropriate sized bus will yield a reliable layout that works well for years. 14 or even 16 will work well for most home layouts. If you are running wire more than 30' in one direction from the DCC station, wire size can be an issue.

Just my 2 cents never worth anything else!

Joe
 




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