Hello everyone,
I am ready to start wiring my new layout. I want to use a power bus wire to connect smaller feeder wires around the track. Since my older layouts were very primitive (just one set of feeder wires) I am unsure what size wire to use. What is a good size wire and where can I find wire to use for a power bus? I have the atlas rolls of 20 gauge wire on hand… will this be sufficient? Thanks in advance , Nick
How big is your layout, how far does the wire have to travel.?
Will it work? What do you mean by work? Will the wire heat up and start a fire? : No not likely.
Will the train move? : Yes the train will move.
Is that what you want? : NO IT IS NOT!
20 ga will work, but what you loose is the slower speeds, since you would have to use a higher voltage to force the same amount of current through the conductor.
14 ga is supposed to be good for DCC, and thus it is also good for DC. I am using 12 ga on my DC layout. LION would use 18 ga for the feeders, and 14 - 12 ga for the bus, but then the LION has 1000’ of tracks!
LION gets his wire from the powerhouse. But then I do not suppose many model railroaders have a powerhouse in their back yard, with miles and miles of scrap wire of every description. I guess you’ll just have to go to your favorite home improvement store and pick up a coil of wire. The LION prefers stranded wire for the bus as it is easier to work with. 18 ga for the track feeders. You could use suitcase connectors, but my use of them did not turn out as well as I had hoped. I should have gone with the bigger suitcase connector for the bigger wire, but my home store did not have any.
ROAR
My layout is smaller than The Broadway Lion’s. I use 18-gauge wire. i have no runs over 20 feet, and most are considerably shorter than that. I use DCC, plenty of feeders, and this works fine for me.
The “standard” recommendation is 14-gauge, and many use 12. 12-gauge is standard wire for a 20-amp household circuit. It will work great, but for me, that’s overkill for anything less than a club-sized layout.
Buy your wire online, at places like Mouser or All Electronics. I have a local electronics place near me, and I often go there, too. Avoid Radio $hack. They sell small rolls of wire at seriously inflated prices.
That Atlas 20 gauge wire would be fine for the feeder wires, but I would recommend standard household 14 gauge wire for the bus wires. I drop feeder wires about every 6 to 7 feet. However, I should (but don’t) wire feeders on the end of every leg of every turnout.
Rich
only
Way back in the 1950s I was an electronics tech an for what it’s worth 14 gauge wire should be plenty big for the normal home layout. Now, there is something else. I was taught that the electrons travel on the surface of the wire only and that is why heavy current draw is feed with stranded wire. This may not even apply to our application, but I did use stranded wire for my buss.
Have a good day
Lee
Interesting.
I use solid 14 gauge wire for the bus, but stranded wire for the feeders.
Rich
Beg pardon, Leo Broadwayensis, but what he would lose is the top end…the speed. If he has to dial in more voltage to get the unit underway, then he will run out of available/deliverable voltage when he wants higher speed at the top end. And this problem with 20 gauge wires used as a bus would probably only be manifest to a neophyte with runs of about 12’ or more, or when he added several hard-working locos at the same time.
Crandell
Him not gonna be happy, Crandell. King of Beasts bring down prey for far lesser crimes than that. Him gonna make you eat your words before him eat you. [8o|]
The ideaof electrons traveling on the surface is the “skin effect” and is minimal at 60Hz powe rline frequencies and even DCC frequencies. The only reason I use stranded for my bus lines is that it is much easier to pull around and through the benchwork then heavy guage solid wire.
My layout pretty much fills up a 10x15 room, and I use #14 for my bus with no slowdowns or power loss. The longest run is about 25 feet.
–Randy
Eh… Wire is part of the circuit. It adds resistance. Resistors affect current. The result could be a loss of voltage, but in my experience that means that suppose a motor will start to run at 2 volts. But suppose it takes 5 volts to get any current to flow through your wire, that means the first electricity that your motor sees is at 5 volts.
In any event, I was able to achieve lower speeds with the bigger wires. LION does not really care about the top speeds, NYCT does not travel that fast. Indeed my trains already run faster than the prototypes.
Yes, the available amperage would depend on the voltage supplying, or conveying, it. But once the motor gets enough volt/amps to turn over at all, that is the start voltage for that system of supply and driven mechanicals. It could be 15% of the range, 55%, or 80%, but whichever extent of the range it is that the motor starts to turn, that will be at the lowest speed, not the highest. What our user will notice is that, when he turns his dial up to max voltage, he’ll still only be at drag speed. If he turns down the dial, he’ll slow to where he started off at a scale mph crawl.
Crandell
Having been at this DC powered model train thing for about 40 years, and being an electrical control system designer back in the days of relays, I have a slightly different take on this.
Why does a DC layout need a bus wire at all?
My average isolated electrical track section (many of you call them “blocks”, I choose not to use that signaling term) is about 20 actual feet long. Each has a single pair of feeders that come from the cab assignment system (some may use rotary switches or toggles, I use relays). Those relays are seldom more than a 20’ run of wire from the track section, usually much less.
All rail joints within the track section are soldered, the feeders are typicially 16 guage wire.
I do a have a throttle bus system of 12 guage wire which connects all the relay panels to the radio throttle base stations. Each of these throttle base stations is powered by its own 5 amp, 13.8 volt, regulated power supply.
Never, in any DC cab control layout I have ever built or been involved in th building of, including a well known club or two, have I seen a need for multiple feeders to a given track section (block).
My trains don’t suffer and voltage drop problems, and I run three and four powered units per train in amny cases.
I don’t know the cross section or resistance of code 83 nickle silver rail, but I suspect it exceeds the specs of 12 guage wire - since DC layouts are almost always broken into track sections (blocks) why would one need a bus and multiple feeders?
Just solder the rail joints.
Sheldon
LION has 1000’ of track, all DC, no blocks. LION uses an Analog Automation System. Him has 10 v DC regulated power supply putting 15 Amps on the tracks. Eight or more trains run at once with up to 12 powered units.
LIONS do not fool around with their trains.
RPAR
Please explain Analog Automation System. Onboard radio recievers?
Sheldon
Analog Automation is of the LION’S own design. Actually I call it Automatic Train Control, but I thought the word “Analog” might help with the description.
Regulated DC power is on all of the layout all of the time. There are no blocks.
As a train enters a station, it passes over a series of resistors slowing it down. Once in the station a gap stops the train in the platform. LION has a time clock that releases trains at 15 second intervals, since a train would always leave the previous station at a known time (say :00 seconds) it will arrive at the next station in say 20 seconds, that station will be hard wired to the clock to release the train (pull in a track relay) at :45 seconds. Again the train passes over the resistors to gain speed.
LION has 45 platform edges on his layout, at the moment only four trains are in service, but the layout will support as many as 12 trains all at once.
Last time I looked, there is only one LION here, and controlling 12 trains, or even six trains is on the far side of impossible. When the LION releases a train from the terminal, it runs the layout, making all of the correct stops automatically. LION does not need to worry about a train until it arrives back at the Dyckman Street Station. There he must align the switches for the 242nd Street station, and then give the waiting train at Dyckman a Clear Home Signal to let it enter the terminal.
There are two loops that in normal operation are separate from each other and from the local tracks that host express trains. These run continuously (making correct stops, of course) but do not need to be turned at the end of the line. The Lenox Avenue Statio>n and the Nevins Street Station (both hidden off stage (sort of) can hold these trains during night time periods so that they can be released to “race” with the local trains.
Here is track with embedded resistors. Thes are 5.1Ω resistors.
Lion,
OK, simple enough and for your purposes a great system. As noted in my post, I don’t care for the use of the term “block” for an isolated electrical section of track, as “block” is a signaling term.
But you do clearly have isolated track sections to effect control, even if they are all connected to the same power at the same time.
Sheldon
True. The left rail as looked at in the direction of travel is ground. The right rail is regulated (+) dc, the trains all move forward. There is no reverse on this layout. Subway trains do not go backwards.
There are power gaps, but not real “blocks” as model railroaders would understand their power districts since there are no cab controls. You cannot isolate one train and operate it as you will.
Actually, the dispatcher does have “holding lights” that are separate from the interlocking system. When illuminated, the conductor must hold his doors open. Perhaps for a connection, perhaps because he is running hot, perhaps because the railroad is all out of joint. Thus if the railroad is backed up, I can hold trains in the stations (by shutting off the relay that would release the train) since there are no train detectors, and because my signal system is just for looks. The LION could build a proper signal system to enforce this control, but the LION is not made out of money. Him would need over 200 train detectors: this is not going to happen. The signals operate off of the same time clock that starts the trains, this looks realistic enough and is all that I can do.
ROAR
Hi Yankee,
Actually I think that skin effect applies only with AC current, and very high frequency at that. Wikipedia says that the skin depth of 60hz AC is 8.5mm. Skin effect might be significant with DCC, because it is roughly equivalent to a few khz. When I Googled “skin effect” one of its’ offerings was for a skin effect calculator, but I didn’t go there to look at it. 14ga wire can carry several amps over tens of feet with nearly imperceptible losses, so it should be plenty for any room sized DC layout.
Regards
Chuck Lee
Skin effect is minimal at the frequencies DCC works at, now at RF the range, it does become a big deal.
Still, using heavy wire for the bus, like 14AWG, is a good idea, as too much resistance can cause all kinds of problems, and most of those problems are caused by inadequate wiring. Cheaper to do it right the first time, than burn out a $100 Tsunami or melt a truck side frame first.
Respectfully I have to ask - did you read the title of this thread? or all the posts in this thread?
The OP is using DC, he has no Tsunami’s to burn out. Skin effect was just a side disscussion, a side disscussion that has no bearing on the OP’s situation in fact.
Again I will repeat my view, most properly planned DC systems do not need a layout bus, but may need a throttle bus depending on the type of DC system. But even with that, each isolated track section should require only one feeder which can often be 18AWG or 22AWG with no problem.
Sheldon