Stranded wire or solid wire?

Either will work fine.  Solid wire is easier for some connections, but if it's going to be repeatedly flexed at all, go with stranded.

Stranded wire is more flexible and maybe less breakable because of that.  Easier to route around a layout or use in areas where it might have movement.  It has been stated that it transmits signals like DCS better.

Solid wire has slightly lower resistance but I find it much easier to make connection with it (solder or mechanical).

I use stranded copper wire for my track power, 12 gauge from transformer to distribution block, 14 gauge to short 18 gauge feeders to track.  Most folks here go one size smaller for each section, especially with smaller layouts.

For most other areas using smaller wire I use solid copper wire.  Much easier to make connections with lever nut or slicing connectors especially with Z-Stuff products.

@CAPPilot posted:

Stranded wire is more flexible and maybe less breakable because of that.  Easier to route around a layout or use in areas where it might have movement.  It has been stated that it transmits signals like DCS better.

I don't know where people get the idea that stranded wire would be better for DCS signals, but it's not supported by any science.   The reasoning for stranded wire is that there is more surface area, but that's only true with Litz wire that insulates every strand.  The propagation on a ordinary stranded wire is usually slower than solid at RF frequencies and the loss is higher.  That would seem to indicate that solid wire would be the choice if you're worried about the DCS signals.

If you use stranded just tin the end to make it easy to go into the lockon

I use O27 track.  Because of the struggles listed by @coach joe above with connecting lockons to it, I bought a whole slew of those MTH lockons with the screw terminals.  I put those (I don't know what they are called - one has to crimp them onto the wire and they have a metal 'U' sort of metal shaped part that is used for the connection) connectors on the ends of all of my stranded wires that I use for track power.  Then I just slip the connection under the screw terminal.

It was a small expense to pay for peace of mind.

I still have to use the old-fashioned Lionel lockons in some places where 2 tracks are close enough together that if I used the MTH lockons the siderods on my steam engines would hit the light part of the lockon.  I use solid wire for those.

walt

I use 14 gauge stranded for flexibility when routing  power supply and track power feeds,   I use smaller gauge stranded for spanning hinges.  Otherwise I use solid wire for crimp lugs, screw terminals and fahnestock clips for easy of connection.

@shorling posted:

"Otherwise I use solid wire for crimp lugs, ...."

I have found that solid wire and crimp lugs can be an issue, as time goes by the wire can become loose just from seasonal variations of temp.  If you use the type of crimper that puts a dimple in the crimp lug, that is better, but to be 100% sure of the connection, crimp and then solder.   Screw terminals and Fahnestock clips are fine with solid.  Part of my job when gainfully employed, was a bi-annual inspection of the tightness of all lugs in power panels, plus checking the mechanical connection of the ground wire from panel to ground rod if it was a mechanical type, not welded.  It is amazing how loose a lug can get just sitting and doing nothing but passing current.  It all had to due with the wire slowly relaxing under the force of the lug or screw

Solid wire is really easy to route which can be huge depending upon the situation.   Not sure it makes much difference electrically stranded or solid, but solid can work harden and break if you have to redo it multiple times especially thin solid wire.  Allowing slack if you want extra at connection points is easier with stranded.  Embedding in foam is easier with solid.  Routing under FasTrack is easier with solid.  Going across a short span without the solid wire sagging is also helpful.

John

i haven't had any issue with solid wire and crimp lugs with 1000's on the layout for over 40 years.  I have encounter an issue with crimping 18 gauge or smaller stranded.  I'm an over crimper which can be an issue.  I use 18 gauge stranded spanning my control panel hinges.   Over crimping work hardens individual strains which eventually fracture  from hinge usage.   I run 18 gauge solid to barrier strips in the stationary control pane interior.  l install an 18 gauge stranded jumper from the barrier strip, over the hinge to the moving control panel mounted switches.

I do have experience with aerospace crimps.  Only stranded wire is used due to the vibratory environment.  The issue there is low density connectors (few wires), small  gauge wire (22-26) with high maintenance access resulted in broken wires at the crimp being the dominant failure mode.   Also under crimping due to crimping tool or operator issues.   

@gunrunnerjohn posted:

I don't know where people get the idea that stranded wire would be better for DCS signals, but it's not supported by any science.   The reasoning for stranded wire is that there is more surface area, but that's only true with Litz wire that insulates every strand.  The propagation on a ordinary stranded wire is usually slower than solid at RF frequencies and the loss is higher.  That would seem to indicate that solid wire would be the choice if you're worried about the DCS signals.

WHAAA???

I don't think that's correct. You're saying the surface area of the wire (each strand) needs to be insulated? (to gain more useable surface area?)

Use of stranded wire versus solid wire for RF purposes | All About Circuits

"When working with higher frequencies, such as RF, it has been suggested to utilize stranded wire when larger diameters are required. The reasoning behind this is that the RF current tends to flow on the external surface of the conductor, whereas direct current propagates through the entire cross section of the wire. Typically, this might be of consequence when sizing a ground wire for some type of apparatus. As an example, consider a 1 ft length of #12 wire:
for solid wire, the peripheral surface area for 1 foot of wire length is :
3.046 square inches
for #12 stranded wire with 7 strands, the relevant surface area is:
8.05 square inches
for #12 stranded wire with 19 strands, the area in question is:
13.25 square inches

"

@Engineer-Joe posted:

WHAAA???

I don't think that's correct. You're saying the surface area of the wire (each strand) needs to be insulated? (to gain more useable surface area?)

Use of stranded wire versus solid wire for RF purposes | All About Circuits

"When working with higher frequencies, such as RF, it has been suggested to utilize stranded wire when larger diameters are required. The reasoning behind this is that the RF current tends to flow on the external surface of the conductor, whereas direct current propagates through the entire cross section of the wire. Typically, this might be of consequence when sizing a ground wire for some type of apparatus. As an example, consider a 1 ft length of #12 wire:
for solid wire, the peripheral surface area for 1 foot of wire length is :
3.046 square inches
for #12 stranded wire with 7 strands, the relevant surface area is:
8.05 square inches
for #12 stranded wire with 19 strands, the area in question is:
13.25 square inches

"

Yes, that's what I'm saying.  It's the whole reason that Litz wire was created!  When you posted your reference, did you read farther than the first post?

@Engineer-Joe posted:

You will realize very little if any advantage where the 'strands' are not electrically insulated from each other --- On the other hand, 'cables' formed of individually insulated strands so arranged as to mitigate (magnetic) proximity effects are highly effective to a few megahertz... Construction info and theory may be found under 'Litz wire' --

Note: I do not recommend reference the Wikipedia article on this subject (for it's over-qualitative, generally 'dumbed down' treatment of same)!

It's also interesting to note that RF cables typically are solid wire, not stranded wire.

Co-axile cable commonly used for TV cable has a solid center.  One of the interesting manufacturing processes was a Copper-clad, aluminum core Coax. Idea was that the RF signal travels on the outer surface of the core conductor. The use of a hybrid product like this is economics.  Copper continues to be an expensive commodity. IMO.  I used solid THHN Copper wire commercially, in general, (500 ft rolls), solid was at least 10% less than stranded.   That may not apply at the Big Box stores.

@gunrunnerjohn posted:

Yes, that's what I'm saying.  It's the whole reason that Litz wire was created!  When you posted your reference, did you read farther than the first post?

It's also interesting to note that RF cables typically are solid wire, not stranded wire.

yes, I read the whole thing. One poster made a comment that you quoted. I still believe that stranded works better in this frequency. I'll have to investigate further when I have the time.

down from your quoted post....

"This is an assertion often found in articles on Litz wire. However, recent research (http://thayer.dartmouth.edu/in.../papers/stranded.pdf) has shown that using stranded wire with uninsulated strands can give a substantial performance advantage over solid wire in the hundreds of kilohertz frequency range, such as commonly used in switching power supplies. The advantage is not as great as with true Litz, but it is had at much lower cost than Litz."

Among the great things about model railroading is that topics like this come up that can spark curiosity about physics of materials and a desire to learn more.  At the same time we get the relief that we don’t need to understand spectral characteristics of electromagnetic fields in conductors in order to run toy trains.

You fellows are way above my level when it comes to wire.  Interesting discussion, though.

I'll stick to air brakes.  

Understanding the principles of electromagnetic fields is not essential to operating model trains, however it can make the hobby more enjoyable with knowledge that makes problem solving less frustrating or the joy of electromagnetic application to new creations.   Motors, transformers, solenoids, relays, command control, Wifi, wiring, etc are all principled on electromagnetics fields.

Here we go again... 

The OP asks a simple question about the use of solid or stranded wire, and you guys branch off into discussions about RF signal propagation, wire resistance, what's better for DCS, etc. Why can't you give a simple, straightforward answer to what is basically a simple, straightforward question?

TO THE OP - HERE IS THE ANSWER:
(Gunrunner answered the question in the second post.)

• If the wire is going to flex, as in a lift bridge application or any other situation where the wires will move, use stranded wire.
• If the wire is not going to move, use solid wire. Easier to work with.
• DONE.