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Discussion Starter · #1 ·
What is the consensus out there on track joins? My layout, under contruction, sits in the attic which experiences a wide range of temperatures from under 10C in winter to in excess of 28C in summer. At the moment I have left all joins (peco flexitrack) unsoldered as I was always led to believe that leaving a few gaps and letting the rails move would prevent buckling due to heat expansion. But is this correct? Would I be better off simply soldering the joins? And how much gap is needed if you leave them unsoldered? I am working on a millimetre or so every three or four lengths of track.
 

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In round numbers a 0.5mm gap in every metre will accomodate rail expansion from a 50C temperature increase, which should be more than enough to cope with temperature variation in the UK. But it is not just thermal effects on the rail you need to think about. How stable is your layout structure with respect to both temperature and humidity? The only reason I have ever found for soldering track joiners is as a work around to obtain a smooth curve when all else has failed. Brian's suggestion of electrically bonding the rails but leaving the rail joiners a sliding fit is the way I would go.
 

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Discussion Starter · #4 ·
Many thanks for advice. That's the way I have been going, more or less, but will tighten up the gaps a bit to make smoother running. I have about 160ft of track to sort out, including a steep, curved elevated section that I probably should never have attempted yet which seems to work, just about. I just hope I am still fit enough to get up the loft ladder by the time this is finished (about 2020 at current rate of progress) ....
 

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My experience in the attic where my min / max thermometer indicates a range of between 5 and 40 C, is that if the sleeper base is not securely fastened, it is more likely to move that the rail in the joiners. This is why I am in the very slow process of relaying everything.

David
 

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Discussion Starter · #6 ·
Ah - relaying is, I find, good for the soul.
So there is consensus that in a hot-cold attic it is actually more important to nail down the sleeper bed properly than worry too much about what is going on in the fishplates?
 

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QUOTE So there is consensus... ?

I cannot recall any other attic dwellers endorsing my experience, so I would be reluctant to say there was a consensus just yet. If we don't hear too many other comments in the next day or so, I could set up a poll specifically to see what ideas can be flushed out of the woodwork, so to speak.

Looking at the problem analytically, with a 40 or 50 degree temperature range, metal rail, especially nickel silver if I remember correctly from past discussions on the Forum, is going to change in length. When push comes to shove, the weakest link is the one which is going to give. In the case of track there are three joints to consider, starting from the bottom:-
  1. Baseboard to track base
  2. Track base to rail
  3. Rail end to rail end

What we really don't want is the track base to rail being the one to give. I can remember at least one post in the past which recounted the tale of a layout where the track had been secured to the base so firmly without any gaps between the rails that the rail lifted from the sleepers destroying the whole thing. So, like so many things in life, it's about getting the balance right. We want the sleepers to stay where they were put and the rail to expand lengthways in the sleepers.

This leads to a conflict between the need to allow the rail to move easily within a rail joiner, so the rail joiner should be loose, and the need for the rail joiner to be tight to ensure continuity of power. I resolve this conflict by powering each rail with its own wire soldered to the underside and connected to the power bus underneath. This allows the rail joiners to be pure "alignment" devices.

Further thought on this subject soon brings the realisation that the baseboards need to be stable as well. A search on "baseboard construction" will reveal rather a large number of discussions on the subject which I think did come to a consensus of "6 to 12 mm plywood primed with emulsion", at least that's what I remember.

David
 

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*** Actually I don't think the actual material is an issue:

The need to have it at a stable condition and seal every surface is the main issue. All timber products expand and contract far more than any metal in the rails - probably several times more in fact. If movement is enough for track bed to be shifted then its not rail... Its timber expansion and contraction!

Consider this - when its hot, rail expands and wood dries and shrinks / when its cold and damp, the opposite happens - the rail shrinks at the same time untreated wood epands quote a lot! We blame it on the rail, but we should look to the WOOD!

There are always screams of "beware" when anyone mentions customwood but its very consistent and stable if used properly. Ply is more user friendly but either MDF or ply will be equally stable if properly supported and painted on all faces and edges when used. MORE stable than any grained timber including all but top quality marine grade ply perhaps!

6mm is THIN for track bed and will need considerable support if the layout is not to become a roller coaster over the years. I would personally recommend never less than 12mm ply or customewood to lay the track on, with supports every 300mm.

the actual baseboard frame can be thinner, particularly if a sandwich style construction is used (two strips of wood with pine blocks separating them at regular intervals, reinforced by blocks at every gusset and join area).

My formula for a stable layout:

Keep timber in the railway room for a couple of weeks before using it. Preferably do all timberwork when its early in a dry period and not either extremely ot or cold.

Paint all wood before cutting it or assembling it - its easier. Use a standard household paint with a little flow aid and a small amount of thinning so it will soak into the wood well - I actually like using a little meths and water rather than plain water.

when the baseboard is cut and assembled, paint all exposed edges and ends before you start tracklaying.

Have a cheap low cost fan heater in the room when doing any glueing - set the heater part to low at most though - the idea is to circulate warm dry air all the while so glue goes off well and moisture is expelled. Leave it on for 24 hours after any work session - just the fan is OK as long as the atmosphere isn't damp.. if its cold and damp, leave the heater on low too.

Fix foam roadbed with good quality PVA full strength. Paint both the roadbed and the area it will be laid then weight it down for at least an hour over its full surface.

Fix track with full strength PVA, no pins (at least none that will be there permanently). weight it down evenly across its length for at least an hour to let the glue tack enough.

Leave a small gap each metre (0.5mm is more than enough if it is regular). Be careful to be sure these gaps are there for curves much more than straight track. never solder rail joiners, just feed every track section with droppers if DCC wiring.

BTW rail joiners aren't all that important if you use bullhead rail or very fine rail - I don't bother with them on bullhead for 4mm scale or code 40 and 55 in HO... but I do always have large radii (5' or more) - I use exactly NONE on my current layout and simply lay the (many many many metres) of track properly aligned.

For layouts with sharper curves and bigger rail sizes (above code 70) they are more important, and a sloppy joiner will cause problems so only ever use NEW joiners - never re-use old ones!

SAME fan heater procedure with ballasting and scenery: ANY water in the layout room should be encouraged to leave as soon as possible.

Use a mix of water and meths NOT water with the glue for these aeas - everything will dry quicker and more thoroughly and the meths will act as the best possible "wetting agent" - much better than dishwashing liquid. Thin the good quality glue at least several parts mths + water to one of glue!

Re a "hot/cold" room or attic. The enemy is changing humidit levels MUCH morethan hot or cold really, except that when things are cold, humidity becomes dampness!.

Leave the fan heater up there. Buy a small plug-in timer and set it to work for an hour at least 4 times per day EVERY day. That will keep humidity and cold stagble across the year and in check and at a low heat setting it will not kill te power bill.

Richard

PS: Its never too late to paint the baseboard timbers.... just more of a pain to do it later. Do a bit at a time thoug, and in no time at all it'll all be sealed with minimal hassle!
 

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Discussion Starter · #10 ·
Many thanks for all advice. My loft must be fairly dry as I have not seen the sort of warping some have described. Adding under-tile insulation has helped a great deal ... I've used full-thickness foil-backed stuff that really cuts down the temperature variation.
Would it be a good idea for me to now paint the timber frames and undersides of my sundeala baseboards anyway to reduce any further risk of warping?
 

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My advice based on thirty years of layouts in lofts and air conditioned rooms is to leave out the rail joiners, leave a 0.5-1mm gap between rail ends on a normal temperature day, and THEN join the rail lengths (as required, allowing for section breaks) like this:

I use garden 'rose' wire (B&Q or your garden centre - the kind used by flower arrangers) which is tinned and flexible (stronger than fuse wire) and make a complete loop (round a small file) in a short length; the ends of this loop are soldered to the rail ends. The loop will allow expansion and remove stress from the soldered joint. The thing will work better if you lightly tin the rail as well. A quick dab with a small iron and Robert's your father's brother. It is similar to the way track circuit wires are done full size. My current layout has used this method for twenty years with no failures. Fishplates are not reliable conductors of electricity as you will find out when showing your layout off to club members.
It has other uses this wire- holding things together while the glue dries, and for soldering awkward parts. One bobbin will see you out.

Alistair Wright
'5522' Models
 

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Discussion Starter · #12 ·
All good stuff ... but I am confused by advice to ditch the fishplates altogether ... when I lay track they form an essential and structurally integral part of the trackwork. Without them, the rails would surely 'ping' out of place, however well glued the sleepers were to the baseboard??
 
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