It may be that you can buy stranded "18 AWG" with 19 strands of 30 AWG, which would be about as close as you can get with 19 exact AWG strands. But, in view of the trouble that wire manufacturers go to, to reduce the diameter of stranded wire to close to that of solid by making compressed and compact wire, I suspect that the 30 AWG strands are actually undersized, so that the overall area is close to 1600 circular mils.
Here is an example of stranding, by General Cable (Click on "CONDUCTOR CHART"):
http://www.generalcable.com/GeneralCable/en-US/Company/ResultQuery.aspx?Query=stranding&Category=all
Notice that there are only two options similar to 19 x 30 AWG: One is 19 x .0092-inch diameter, for 1608 circular mils. The other is 16 x 30 AWG, which comes out to about the same area.
In any case, I think we agree that the only reason for stranded wire is mechanical flexibility. However, I have described before the old telephone-switchboard trick of aligning a cable with the hinge and fastening one end to the stationary part, the other to the movable part, so that the wires are just twisted through about 90 degrees and not bent at all, done entirely with solid wires!
Bob Nelson
lionelsoni wrote:"The resistance ratio of n strands of bare wire placed parallel and making contact with one another is found by experiment to be the same as for a round solid wire which has the same area of cross section as the sum of the cross-sectional areas of the strands; that is, n times the cross section of a single strand."
"The resistance ratio of n strands of bare wire placed parallel and making contact with one another is found by experiment to be the same as for a round solid wire which has the same area of cross section as the sum of the cross-sectional areas of the strands; that is, n times the cross section of a single strand."
But remember that solid and stranded wire of the same size have diffrent cross-sectional area. for example looking on the standard american wire gauge cart, the standard wire is designed to.
#18 solid has a circular mil area of 1620.0
and a #18 standard 19 strand wire has a circular mil area of 1900.0
19 strand wire is the standard number of strands for wire over size 20awg. the wire that make up the strands are standard wire sizes as well and this is what creates the diffrence in over all area between solid and stranded wire. Now you can buy stranded wire with more of less strands and get a closer match. The wire with a larger cross-section will have less resistance, but this diffrence will be very minor and will not affect anything in our hobby world.
For example using #18 again solid has a resistance of 6.6 ohms per 1000 foot and stranded has a resistance of 5.5. A diffrence of only 1.1 ohms per 1000 foot. Larger size wire, say #12, this diffrence is almost completly null.
Treat using stranded and solid as your personal prefrence, as far as our hobby is involved the only time I can think one may be better then another is solid for a control panel. ONLY because when you bend solid it retains its shape, stranded has more flex in it and must be fasten down or together to keep a neater appearance.
One last note to metion because stranded is comprised of smaller solid wires if you need a wire to move say for a hinged bridge to swing to open a isleway, stranded is more flexable and should be used.
John
In my last posting, I hesitated to quote the National Bureau of Standards Circular C74, since all I had was someone else's Internet posting. I do now have a copy of the 1937 reprint of this authoritative book; so here goes, from section 76:
The "resistance ratio" is defined as the ratio of "the resistance at frequency f" to "the resistance with direct current or very low frequency alternating current."
Tex702,
What kind of switches are you using? If using Gargraves switches you may find that some of the older switches break the circuit at the switch for the center rail(both output sides, straight & curve), also Gargraves track may be insulated at the switch for one or both outside rails on the 072 switch size.
The best way to check for a lack of power is with either a multimeter or a lighted car on the track, push the car by hand to see where the power goes out.
Lee F.
Doug,
Tin the ends of stranded wire, or use crimp-on spades, and it inserts into lock-ons very nicely.
Chris
There is no electrical reason for preferring one over the other. It is purely a matter of convenience, in that stranded wire is more flexible, as your experience indicates. Stranded wire has the same amount of copper as solid wire of the same gauge and therefore the same conductivity.
I think that some of the superstition regarding stranded wire comes from a confusion between simple stranded wire and what is called litz wire. Litz wire is a very special kind of stranded wire whose individual strands are insulated and braided together in a complex way to mitigate what is called the skin effect. The skin effect increases the apparent conductivity of a wire by confining the current to the surface of the wire. It increases with frequency; but, at 60 hertz, the skin depth is 8.57 millimeters, much more than the thickness of the entire wire and therefore not significant. In any case, simple stranded wire would not be any better than solid wire.
Stranded wire is not as much larger than solid wire as you might think, because it is normally compressed after stranding, to close up the gaps somewhat between the strands. Even so, you might imagine that the small increase in diameter increases the skin effect by making the wire diameter closer to the skin depth. But the skin depth increases in exact proportion to the diameter because of the presence of the gaps between the strands.
In CTT this new issue has the STAR WIRE PATTERN. This is what I and lots o GIZ use here on the forum. The jest of it is to run a heavy set of paired wires, from your transformer to a central location the split them from there to the areas of your track. I use stranded 16 gauge that I bought at an army navy store, 400 ft for $20. I used a set of piano hinges and took the hinge apart seperated them and have one side common and one side hot. I then drilled holes in the hinge for the track to hook up to. One side common one side hot. Very easy works great no problems.
laz57
Doug Murphy 'We few, we happy few, we band of brothers...' Henry V.
Sounds like a large layout and that you are pretty far along. Keep my observations in context.
There are a number of threads in this forum that go into a lot of detail about a power bus. That is the way to get power, as bob has described, around the layout most easily. Stranded wire, 12 or 14 g thru barrier strips around the layout. Then feeder connections from the power bus to the track about every 6-8 ft. That would give you power around the layout. There are a lot of posts, in the newbie section as well, on how to get these feeders done expeditiously.
That said, you may have some other considerations you may want blend in. That is breaking the layout into parts --power districts -- so that you can control the power and what happens at different points in the layout. EG, power to one engine on a siding in the yard but not all of them. Threads here explain how to do it. If you plan to do this, consider colored wire for each power district/block.
That is a big layout to power. You didn't describe your power source. Keep in mind the wattage that your layout will consume. A lighted passenger 5 car train draws a lot of watts.
You may also want to think thru accessories and lights that you may wish to power later on. How will you do that. Again, browse the posts here for a lot of info on that subject.
Don't hesitate to ask any question. haven't seen a dumb one yet,.
hope this info helps.
ralph
Can you supply more info. Such as the type of track you are using as you mention flextrack.
How is the layout presently wired ? Are there feeder drops to a main buss or some sort of paired wiring ? Or are you simply using terminal tracks ? Are there blocks with toggle switches ?
Are you running conventional opperation or command control ?
What you're proposing is very commonly done, Tex. If you try it, be sure to use heavy-enough wire. The track itself is typically equivalent to 16 AWG wire; so you should use something heavier than that. I recommend 14 or 12 AWG, which is easy to find in home-improvement stores and not too expensive. You can get it stranded in many colors and as non-metallic sheathed cable ("Romex").
An important consideration is how much current your transformer can put out. The wire should be able to carry that much safely. Use 10 AWG for 30 amperes, 12 AWG for 20, 14 AWG for 15, 16 AWG for 10. If you have a small transformer, keep in mind that you might have a bigger one some day and will not want to redo the layout wiring.
Another thing you could try is soldering the rail joints together. Your layout is small enough that, if you got the joints reliably connected, you probably wouldn't need extra feeder wires at all.
Our community is FREE to join. To participate you must either login or register for an account.
Get the Classic Toy Trains newsletter delivered to your inbox twice a month