Not knowing a whole lot about electricity let me ask, … I had lots of small gauge CAT wire around to use on a bit of an expansion, Now this is smaller than anything else I have used…it is 26 or 28 gauge.
I realize my heavier drop feeders will carry current better, but will something like 28 gauge actually heat up or anything with 18 VAC and 3 amps? Afterall this is still heavier than some of the decoder wiring inside the locos.
Thanks.
You should be safe with that gauge wire, depending on how many locomotives and/or lighted passenger cars you may have in a particular section of track, and how often you have feeders. If you have feeder wires every 3 or 4 feet you’ll be okay, but if you have only one set of feeders for 10 feet or more of track and have several locomotives within that section, it could be putting a heavy load on the wire.
Where did you come up with the 18 VAC 3 Amps figure? Are you running Lionel O scale? If you have HO or N, you should not be putting AC voltage on the track. Even DCC should not be measuring more than 14.5 VAC measured with a simple VOM IAW NMRA DCC Standards and Recommended Practices, and 3 Amps at that voltage is not a very heavy load. If your 3 Amp figure is based on the output of your DCC booster, its internal circuit breaker should shut it down if you put more than 3 Amps of load on it.
Keep in mind that the total load your system will handle won’t be going through one set of feeders under normal circumstances. Unless you have only one set of feeders for the whole layout, or you’ve parked all your most power-hungry locomotives on the same feeder-section of track, you shouldn’t have a 3 amp draw through any particular set of feeders.
With that wire gauge, three amps continous could get pretty darned warm. If you can keep those feeders to short lengths of track where only two locomotives are likely to be at work hauling any ‘tonnage’, you should be fine, even with sound-equipped locomotives. Add a significant length, grade, or sticky drive, even heavier hard-rolling cars, and your amperage draw will rise. Three sound equipped locomotives working hard over a 10 foot length powered via a single pair of those lightweight wires is probably not a good idea.
See this site for a chart where they discuss the current ratings for wires of a certain gauge:
http://www.powerstream.com/Wire_Size.htm
Three amps is a bit optimistic for the gauge you are thinking of using, regardless of whether it is for power transmission or chassis wiring.
Hi,
My advice… put the thin wire away for another use, and buy the proper size feeder wires for the layout. Like benchwork and tracklaying, wiring is a cornerstone of a trouble free layout. Of course the small wire will work, but not as well as the proper 20-22 size.
Remember, its a lot easier to do “it” right up front, rather than to go back later on and replace.
Thanks, Gentlemen.
Pardon my mistyping…my layout power is 15 VDC @3 amps.
No, I have lots of feeders…most 18 to 22 gauge and every three feet at the most.
I had just put the lighter wire on the service tracks and bridge track of my newly installed turntable.
Not to worry. Looking in a copper wire table I find that #26 copper wire has a resistance of 40.81 ohms per thousand feet. That means a one foot #26 feeder has a resistance of 0.04081 ohms. Power (heat) is given by the formula P = I**2 * R. So a one foot feeder made from #26 wire and carrying 3 amperes would dissipate 0.4329 watts, which won’t heat it up at all.
Number 28 copper wire has a resistance of 64.90 ohms per thousand feet. Same calculation gives a power dissipation of 0.5847 watts for a one foot feeder. Again not enough power to make it warm up.
For mechanical reasons I prefer #22 or #24 for feeders. I personally find anything smaller than #24 is hard to strip, my long nose pliers may not grip it, and it is so fine that I have trouble seeing it. But these are mechanical issues, not electrical. In actual fact, the resistance of one foot of any gauge of wire big enough to see, is so close to zero as makes no matter.
Thanks, Mr. Starr. That’s the kind of opening one likes to see in a response. You fellows with the know-how make this forum a great place to hang out.
Much appreciated.
There are 2 other considerations besides just heat in the wire:
voltage drop stays reasonable
circuit breakers function properly
If the feeder is kept to the 1ft length, the voltage drop at 3 amps is less than 0.2 volts with 28 gauge wire. Not a problem in DC or DCC.
Circuit breaker function is harder to calculate, but easy to test. The quarter test is a great test, and not just for DCC. The quarter test mimics the short circuits that occur from derailments and/or metal objects laying across the track. You want the circuit breaker to pop when the quarter is laid across the track,. You ideally want the current to be cut off (or at least be limited by the device to a low value), rather than having 2.9 amps flow continuously through the thin wire and wheels on your tr
There are 2 other considerations besides just heat in the wire:
voltage drop stays reasonable
circuit breakers function properly
If the feeder is kept to the 1ft length, the voltage drop at 3 amps is less than 0.2 volts with 28 gauge wire. Not a problem in DC or DCC.
Circuit breaker function is harder to calculate, but easy to test. The quarter test is a great test, and not just for DCC. The quarter test mimics the short circuits that occur from derailments and/or metal objects laying across the track. You want the circuit breaker to pop when the quarter is laid across the track,. You ideally want the current to be cut off (or at least be limited by the device to a low value), rather than having 2.9 amps flow continuously through the thin wire and wheels on your tr
The rail itself is going to act as a conductor between feeders, so smaller gauge wire is no problem if you have an adequate number of feeders.
sounds like someone came into a bunch of old telephone wiring cables. right?
i wired my entire layout with that stuff and just doubled it for the any run over a couple of feet and stepped down to single wire for the last couple of inches where i soldered it to the rail.
i did use a bare number 10 copper wire for a grounding buss under the entire layout.
i operate ho scale straight dc and mu up to 3 atlas geeps on 35 car trains with no noticeable voltage or current drop in any block. longest wire run is about 15 feet from the control panel to the track. feeders are no more than 6 feet apart in any one block. same spacing for drops to the ground wire.
charlie
I use some very small (26-28ga) wire but only for about 4-6 inches and then it is soldered to a 20 ga wire the goes to the bus wire. I use solid copper for these at the track and use the flattened wire end to simulate a spike, then solder it to the rail. A little more work but the looks can’t be beat. Just another way to ’ skin the cat’.
-Bob
Cisco, your new turntable looks good.
How large is that turntable?
Are you happy with the purchase?
Thanks.
I’ll throw in a few tips because that is what I like best about reading forum posts myself.
This is the Walthers assembled 130’ Cornerstone turntable that finally arrived for all those who ordered years ago. Mine took two and a half years…due to the manufacturing issues with the electronics or operation.
So far it works well. It installs very easily and programs easily and accurately. The pivot movement is very stable.
The detailing is nice and crisp. Mine came with an extra set of handrails.
I chose to control it with the control box provided rather than using the throttle to program the DCC decoder that is built in…on advice from those with experience in this forum.
I bought a switching power supply ( 5 bucks more than a similar Class 2 power supply) that will provide exactly the voltage and amperage listed on it (16VDC 1 amp), and because it was slightly more amperage than recommended, I installed a .5 amp quick fuse on it. I don’t expect any issues with it, however.
My installation tips:
Check the turntable bridge wheelsets. One of mine had fallen right out with its carrier…but I found it in the box and it easily snapped back in.
The tracks on the turntable bridge can be pushed a few millimeters back and forth in their rail plates (similar to the one rail in a piece of flex track) if they are not exactly even on both ends of the bridge. It had to be done on mine as one rail was definitely too far forward on one end. This is not explicitly stated in the instructions.
The bridge reverses current at 180 degree spots to work properly. Don’t forget to reverse the current in your service tracks on the two sides of the 180 swing to match the bridge track.
Looking at the turntable at our local rail museum I really thought I should weather it up a bit in the pit. Weathering is not absolutely necessary; I’ve seen pictures online of
Hmmm…I wonder if they have changed the design from their first built-up indexed models. I have one of their 90’ers released in 2006. It reverses itself with a split ring design, so the idea is to leave all radials and approach with the same polarity. At least, that was the way I did it, and my turntable performed flawlessly, including not causing any polarity disparities.
Crandell
Yes, you are partly correct, Crandell.
The split ring is part of the design. Certainly in mine. Therefore there are two “dead” service track spots at 180 degrees from one another. The service tracks on either side of those spots need to have the polarity reversed…if my turntable is typical.
Just double checked it now to be sure. Yup. Just so.
(But bearing in mind I did start this thread with the admission that I know little about electricity…I always stand to be corrected…and almost always get something wrong before I get it right.)
Just kind of thinking this through, and if you have a long continuous block of track, fed by #22 or whatever guage wire you are using as feeders from a continuous bus, each feeder per side is going to carry only a portion of the total current. Each feeder will essentially be in parallel with each other from each bus wire to it’s corresponding rail. About the only way a feeder could carry the full current being drawn from the track is if it were a single feeder to a segment of rail.
Yes, and since most layouts are discontinuous at the railhead, that is they are gapped, and therefore powered via individual feeder pairs at times, if a dead short happens at a place where there is only one set of feeders and the full rated power supply amperage goes through that one section, which it will since that is where the circuit is shorted, the weakest link thermally will be the first to suffer. That may be a decoder or it may be a feeder tucked firmly against papier mache or wood.