expansion joints with hand laid track

PK Jan 7, 2016

  1. PK

    PK TrainBoard Member

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    I've searched threads on expansion joints and they all seem to have one thing in common: flex track. The rail can slid in the plastic spikes holding it to the rail. My question is what about a length of handlaid track using soldered PC ties. Once the ties are glued down & ballasted, it would seem the rail can't move without breaking something. I'm laying soldered track on 1/2" plywood & 1/2" homasote. Specifically, a line of turnouts several feet long. Is there anything special I should do in this case or do the normal expansion joints several feet apart work?
     
  2. Rodsup9000

    Rodsup9000 TrainBoard Member

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    Paul,
    I built a small loop of Nn3 with code 40 rail soldered to pc board tied as a test bed. I glued all the ties down on a sheet of homasote with about every 7th tie being a pc board tie. Inside of a few weeks, some of the rail pulled the copper off the fiberglass on the pc ties. It was caused by the expansion of the homasote due to humidity. I have since switched to using Micore instead of homasote and haven't had any problems. Micore is a fiberglass based and doesn't adsorb moisture but may be hard to find.

    You might get away with homasote if you were to paint all sides and edges with 3 or 4 coats of paint to seal it well from moisture.

    Rodney
     
  3. Inkaneer

    Inkaneer TrainBoard Member

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    WOW, 1/2" plywood and 1/2" Homosote! That is a waste of material as well as time and effort. Plus it won't do what you would like it to do and that is prevent sagging between vertical supports. It will sag, just give it time. I use thin plywood commonly called 'luan' or underlayment. Generally it is 1/4" or less thick. For roadbed I use cork. I support this with splines made from 1/8"thick 'Masonite' or hardboard that is cut in strips (splines) 1" wide. These splines support the roadbed every inch of the way. It is light weight, strong, inexpensive and does the job. Before assembly everything is painted with a good wood primer. Two coats would not hurt. As far as the rail is concerned, a gap of .0015" every length (30-36inches) would be sufficient for rail expansion. That would give you protection for a temperature swing of about 43-44 degrees F. So if you laid the track at a room temperature of 70 degrees you would be safe up to about 113 degrees F. If you needed more protection then cut the rail after you laid it into smaller segments. Rail expansion is a co=efficient. That means it depends on two variables, the increase in temperature and length of rail. Halving the rail length doubles the temperature.
     
  4. montanan

    montanan TrainBoard Member

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    I can't help with N scale, but I started my HO scale layout with hand laid code 70 tracks and turnouts over 25 years ago, using Homabed homasote roadbed and haven't had and haven had any expansion problems. I ended up completing the layout with Shinohara code 70 products and again no expansion problems. My layout is in my basement and the temperature variation isn't too much. In the dead of winter with no heat the room may get as low as 50 degrees and in the summer on the hottest day I doubt that the room gets to 70 degrees. (a great place to be on a hot day).
     
  5. Inkaneer

    Inkaneer TrainBoard Member

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    But not everyone is blessed with climate controlled environment and even those who are have to factor in the potential of losing electric power. AC and forced air heat don't work without electricity. There are layouts in unheated attics, garages, outbuildings and basements where temperatures can swing through a range of 100 degrees. And expansion is not the only thing to be concerned about. There is the opposite problem of contraction. Metal will contract the same amount with a drop in temperature as it will expand with a rise in temperature. Curves are especially susceptible. Of course, MR Rule No.1 applies so . . .
     
  6. BoxcabE50

    BoxcabE50 HOn30 & N Scales Staff Member TrainBoard Supporter

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    I wish that my house could be so even. I am envious!
     
  7. bill pearce

    bill pearce TrainBoard Member

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    Once again the ugly spectre of expanding track visits us. I have had this explained by a trained metallurgist, the expansion of metal track, like NS, due to changes in temperature is insignificant. The expansion of wood is HUGE. On my next layout I will cover all plywood with a good coat of shellac on all surfaces. That should cover our humid summers. And since I may decide to use handlaid code 40, who needs expansion joints?
     
  8. BoxcabE50

    BoxcabE50 HOn30 & N Scales Staff Member TrainBoard Supporter

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    And hopefully none of the supporting wooden framework will shift from humidity....
     
  9. Inkaneer

    Inkaneer TrainBoard Member

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    Your metallurgist friend should define insignificant. Show him a picture of a "sun kink" in prototype welded rail and ask him if that is insignificant. Hint: the prototype RR's don't think so. But laying aside the 1:1 world how about our world of 1:160? As I pointed out above the expansion of metal is expressed as a co-efficient. That means that there are two factors involved, one is temperature, the other is length of the piece of metal. So let's say we have a layout that is a basic 4 X 8 sheet of plywood and has a loop of track with a total length of 18 feet. The track is soldered together into one continuous loop. Now let's say that when the track was laid it was done at a room temperature of 70 degrees F. Now lets put the layout through a temperature change. Let's say the layout is in a non climate controlled garage and is subject to a temperature range of 0-100 degrees F. That would equal 70 degrees of contraction and 30 degrees of expansion. The question is how "insignificant is the effect on the track. That is a simple math problem. Take the 30 degrees of expansion multiplied by the 18 feet (216 inches) of track. That equals 540 (6480). Now we have to multiple that by the co-efficient of nickel silver. But nickel silver is not a chemical compound with specific proportions. It is an alloy where the components can be varied. Generally the coefficient used is about .0000096 per degree per length. Now .0000096 may seem like an insignificant amount. But let's plug it in to our situation. We have 540feet X .0000096 = .005184 feet. Now convert to inches .005184 X 12 = .062208. That is about 6/100th of an inch. That is not insignificant when you realize that no expansion was planned for when the track was soldered together into one piece. That metal will expand and it will do so at the weakest point. So the rail pops out of the plastic tie plates requiring repair. But look at the other side when the rail contracts. There we have a 70 degree drop in temperature. Now the rail contracts .145152 inches and it again pulls out of the tie strip. But the point is that rail will expand with even the slightest change in temperature and the longer the piece of track the expansion will be proportional.

    People who solder all their track together usually do so only once. The prototype tries to channel rail expansion vertically rather than horizontally but are not always successful. We can't do that unless you want to glue the rail to every single tie and then hope that ballast will hold the ties in place. Most people will just gap the track.

    As far as the effect of humidity on wood and wood products, take the time to seal the wood (all sides) with a coat or two of primer or wood sealer (do the cork too). At least two coats on any end grain and you should be okay.
     
  10. tracktoo

    tracktoo TrainBoard Member

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    Expansion is very real as has been demonstrated and is probably worse with humidity and wood than just temperature with metal rail. Wouldn't this be an argument for using metal or plastic rail joiners without soldering, affording some mechanical aid in holding alignment, but then soldering jumpers or drops to a buss wire for assured power delivery? And maybe doing nothing (unless they are difficult to access) having the option of adding jumpers later if a problem arises with the joiners, knowing that it could?
     
  11. Inkaneer

    Inkaneer TrainBoard Member

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    If using flex track a good rule of thumb is a power feeder for each section of track. Rely on the metal rail joiners for alignment not transfer of electrical power even though in sectional track the joiner is used for power transfer.
     
  12. robert3985

    robert3985 TrainBoard Member

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    A big part of my layout consists of hand-laid code 40 track. My layout is built in 6' portable sections and on my four 6' Echo sections, at least half of that LDE is the Park City Yard...which is totally hand-laid code 40. The layout is portable, and visits as many as four shows in any given year...being transported in a large U-Haul trailer both in the cold and in the Summer heat, and I have never had any "kinking" problems with my hand-laid track (nor with my ME code 55 trackage either).

    Here's how it's constructed: (1) Subroadbed is splined Masonite glued together with yellow carpenter's glue, and the top is sanded smooth (2) Roadbed is Midwest Cork Products N-scale cork...or sometimes HO scale cork...which gets glued down to the splined subroadbed with yellow carpenter's glue...then sanded smooth after it's dry (3) Using a homemade jig, I lay in wooden ties with every fifth one missing and glue them to the sanded cork roadbed using yellow carpenter's glue (4) I then lay in PCB ties in every unoccupied space between wooden ties (5) I then carefully sand the wooden ties down to the same height as the PCB ties (6) I buff the bottoms of my rail and the tops of my PCB ties with a pink pencil eraser and (7) carefully solder the first rail onto the PCB ties (8) Second rail goes on being held in place with three Micro Engineering code 40 three-point track gauges, then I (9) gap the copper cladding on each PCB rail with an oval jeweler's file, staggering the gaps so they're not centered or in the same spot on every PCB tie (to make the gaps much less visible).

    General construction notes: (A) I stagger the joints where the rails join up using four PCB ties so that no rail joints are directly across from each other (B) I solder a 6" long 22 AWG solid copper feeder to each and every piece of rail on the layout no matter how short (I flatten the copper wire, tin it, then solder it to the underside of the rail) (C) All rail and track solder joints are fluxed with SUPERSAFE Superior No. 30 liquid or gel soldering flux (available here:http://www.ccis.com/home/hn/page2.html) and 96/10 Tin/Silver solder (available here: http://www.ccis.com/home/hn/page5.html) (D) I always...ALWAYS...thoroughly check and run trackwork to ensure it's flawless both electrically and mechanically before painting, ballasting and weathering.

    If you decide to solder your feeders to your PCB ties, make sure that both tops and bottoms of the PCB ties are gapped...or you WILL have phantom shorts.

    I have had zero expansion/contraction problems with my portable layout sections using handlaid code 40 track, but my layout stays in a nicely climate controlled layout room until broken down for transport several times a year. At shows, I also don't have problems, either in the Winter or Summer.

    The only time I have had kinking problems were on unfinished bridge sections where the track "floated" unsecured over roadbed that was going to be removed later and replaced by a bridge.

    From my 30+ years of doing handlaid code 40 track, soldered to PCB ties, it is evident that "slippage" of rails between plastic spikeheads is not necessary to eliminate expansion/contraction kinks, and that sturdy, stable roadbed and subroadbed keep the rails straight.

    Cheerio!
    Bob Gilmore
     
  13. Inkaneer

    Inkaneer TrainBoard Member

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    Bob, your layout goes from one climate controlled place to another. You probably are not exposing the layout to a temperature difference for any great length of time while it is in the U-Haul trailer so the rail would only gradually lose heat and thus gradually shrink. Plus your layout is sectional so the length of the rail is limited. Recall that expansion is a coefficient and the longer the length the more expansion. So you are limiting both the temperature difference and the length of the rail. Now on the other hand, our Ntrak layout is stored in a trailer that is parked in a storage yard. Definitely not a climate controlled situation. At a train show, set up is started on a Friday night and completed the following morning. If, during winter, on Friday night, a tight fitting joiner track is inserted between adjoining modules, we find, come Saturday morning, that the joiner track is bowed either horizontally or vertically . Conversely in the summer a piece of tight fitting joiner track will have to be replaced by a longer piece.
     
    Last edited: Jan 10, 2016
  14. PK

    PK TrainBoard Member

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    Thanks for the replies. To clarify, while I have a loop, I'm not soldering all the track. First, I have a block of turnouts on both sides with the longer block being just over 3ft. If I need to be concerned about expansion in that, I can break it into shorter sections. My bigger concern is the curves at the ends. While the track will be ME flex, I have curved turnouts at all 4 corners of the layout. I normally solder all joints in curves and was planning to solder the curves into the turnouts. That leaves ~48" of track with a soldered turnout at each end. I'll have gaps in the straights. I've been building for a while and just started wondering about this. The benchwork is finished and painted top & bottom, but nothing is glued down so this is the time to make sure I'm not doing something wrong.

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