Peco rail expansion

[Dagworth]

I'm laying fiddle yard track at the moment (code 100 OO), my fiddle yard boards are all 4ft long with track rigidly fixed to screws and PCB sleeper at each end. Track is pinned every four inches. Invariably there is an unsoldered rail joint somewhere along each board. It's 15 degrees C in my railway room at the moment, how much gap would be advisable to leave for expansion at the mid-board joints?

 

Thoughts would be appreciated

 

Andi

Edited March 4, 2023 by Dagworth

[Vecchio]

considering a temperature range from 0 to 40 deg C your expansion from 0 to 40deg C would be approximately 0.8mm.

 

This is based on an expansion coefficient of 16.2 x 10E-6 m/deg C 

 

not very formula friendly this forum...

[Oldddudders]

I cannot give you a scientific answer, Andi, but can state that a couple of years ago I found a serious track buckle in my Peco Code 83 fiddle sidings, which are circa 10' long. There was an offset of a good inch or more. Admittedly the outdoor temperature occasionally reaches 40 C, but the railway barn has 18 inch thick walls and small windows, so doesn't absorb the heat as badly as it might, and the sidings don't get any sunlight. Allow about 2 mm at each joint and you may avoid the worst effects. 

[F-UnitMad]

5 hours ago, Vecchio said:

considering a temperature range from 0 to 40 deg C your expansion from 0 to 40deg C would be approximately 0.8mm.

 

This is based on an expansion coefficient of 16.2 x 10E-6 m/deg C 

 

not very formula friendly this forum...

I would agree with this, pretty much. I left a gap of 1mm approx between rails, in my loft, which is fully insulated but can fluctuate in temperature.

In the heat last summer I found only one small distortion out of gauge, it was a turnout rail with less spikes in place. The layout is U.S. O Scale, Code 125 & Code 100 rail spiked through coffee-stirrer ties (sleepers).

Mindyou, it looks like this anyway - not from heat distortion!!

[JeffP]

Do the plastic sleeper bases expand too?

[Phil Bullock]

Just don’t let Mike Walker set you up over the radiator in St Margaret’s Hall! That will exceed all logical formulaic calculations!

[Dagworth]

29 minutes ago, Phil Bullock said:

Just don’t let Mike Walker set you up over the radiator in St Margaret’s Hall! That will exceed all logical formulaic calculations!

We’d need all the radiators on to make up for the missing wall to make the layout fit! 
 

Andi

[Phil Bullock]

2 minutes ago, Dagworth said:

We’d need all the radiators on to make up for the missing wall to make the layout fit! 
 

Andi

You and me too! 

[ISW]

On 04/03/2023 at 13:46, Dagworth said:

my fiddle yard boards are all 4ft long with track rigidly fixed to screws and PCB sleeper at each end. Track is pinned every four inches.

With 'discrete' pinning I can see how the track can laterally buckle/move between the pins. However, if the same track was glued down (with, say, PVA) then what is likely to happen? My guess is that some of the track would 'lift' vertically peeling away from the PVA. 

 

Does anyone have experience of this?

 

Ian

[Harlequin]

33 minutes ago, ISW said:

With 'discrete' pinning I can see how the track can laterally buckle/move between the pins. However, if the same track was glued down (with, say, PVA) then what is likely to happen? My guess is that some of the track would 'lift' vertically peeling away from the PVA. 

 

Does anyone have experience of this?

 

Ian

Yes, Peco Code 75 PVA'ed to 3mm cork, 1440mm long sections of track with no expansion joints soldered to copper clad at each end which is screwed to the ply deck below.

 

Result in hot weather: The rails had nowhere to go and so they buckled sideways, undoing the PVA bond between the sleeper-base and the cork.

 

[Fat Controller]

43 minutes ago, ISW said:

With 'discrete' pinning I can see how the track can laterally buckle/move between the pins. However, if the same track was glued down (with, say, PVA) then what is likely to happen? My guess is that some of the track would 'lift' vertically peeling away from the PVA. 

 

Does anyone have experience of this?

 

Ian

It would probably pull out of, or break, the rail fasteners at the sleepers, rather than breaking the glued joint. This certainly happened on some track on  my garden railway during the summers. To reduce deformation, might it be an idea to fix the sleepers 'outside' the running rails?  They would act in the same manner as the built-up ballast 'shoulders' to be seen on the prototypes.

[ISW]

8 minutes ago, Harlequin said:

Yes, Peco Code 75 PVA'ed to 3mm cork, 1440mm long sections of track with no expansion joints soldered to copper clad at each end which is screwed to the ply deck below.

 

Result in hot weather: The rails had nowhere to go and so they buckled sideways, undoing the PVA bond between the sleeper-base and the cork.

 

Phil,

 

Interesting that it replicates 'real life' almost exactly. I just wondered if 'lifting' would be more likely. This is what happens if you remove to many rail fastenings in real track:

 

You can just imagine the compression forces in the remaining rail!

 

Ian

[Chris M]

I've had N gauge rail come away from the sleeper base in very hot weather. This was track that had nowhere to go. In storage sidings with pins spread out the track at least has some wiggle room. It is surprising how much it moves. I actually had the opposite problem when things got very cold - the end of the rail contracted past the end of the rail joiner. That of course is down to bad workmanship.

 

[Vecchio]

Just a little photo and why I prefer code 100 over code 75...

On that particular day the temperature was 34.2 deg C in the shed.

 

 

20180716_205457 

[ERIC ALLTORQUE]

some ice cubles in plastic containers in the summer if the heat waves are going to continue it seems,or lay track on hot days and it should sort itself out in joiners for winter.

[The Johnster]

Back in my teens, my layout was in the loft, converted for the purpose by Buffalo Bill Enterprises PLC, aka my dad.  His concept of insulating was to lay old newspapers between the joists and lay planks on top…. This was the late 60s, my first ‘proper’ layout, to my own trackplan

 

This was the first layout I had that used flexi, GF Formoway, and Buffalo had got me some fibre-sleepered yard long straight (Kemilway?).  Callow youth that I was, I laid it with the greatest care I could muster, each track section smoothly and gaplessly joined with proper track joiners to the next.  The trains ran perfectly, by the standards of those days at least!   
 

Buffallo’s conversion was heated in winter with a paraffin stove; he was a big fan of these death traps.  This was effective enough to cause condensation but not to prevent freezing conditions in winter and oven temperatures in summer; I took a thermometer up there and recorded 2 degrees F, and 107 deg. F only 3 weeks later.     Needless to say, the layout tore itself apart, and had to be relaid, with most track damaged and having to be replaced.  Buffalo’s advice was to not pin it down next time, but it never really worked properly after the first couple weeks because of the insane temperature range.  And the condensation from the deathtrap heater rusted everything.  
  

I resolved to never again contemplate siting a layout anywhere other than within the heated and ventilated living area of the home, or a space that could be permanently heated and ventilated to that extent, which resolution I’ve kept to, even to the extent of not taking opportunities to build in garages, sheds, or lofts.  These are fine locations, and many of us have no other option, but the cost and labour required to bring such premises up to the ‘livable’ standard I require has always been beyond me, and relying on Buffalo was a proven non-starter. 
 

An advantage to having the layout in the living area (mine shares the bedroom of a two-room flat) is that it is instantly available and accessible; I can make a shunting move while the adverts are on, and do the nextmove next .  And heating/ventilating it is free, as the flat has to be heated and ventilated for 24/7 occupation anyway.  I’ve left small gaps in my rail joints, which close up in warm weather but have not caused any distorion so far, and do not open out in cooler conditions enough to make trouble.   I worry a little when all the gaps in the run around loop are closed up, as that track has nowhere left to go, but we’ve got away with it so far; this will be the layout’s seventh summer!

 

Track is Streamline code 100, pva’ed direct to the baseboards and further fixed in position by pva’d ballast; my view is that track fixed firmly to a level baseboard is a major component of reliable running.  I still use rail joiners to ensure smooth joints between sections, and cut notches in lengths of flexi to represent fishplates for wheelbeats; these, and the joints, will eventually be given cosmetic fishplates, which sounds like a nice gentle Sunday afternoon job…

[Happy Hippo]

22 minutes ago, The Johnster said:

 

 

This was the first layout I had that used flexi, GF Formoway, and Buffalo had got me some fibre-sleepered yard long straight (Kemilway?).  

Wrenn track was the fibre sleepered stuff.

[The Johnster]

Wrenn, then.  It didn't like the damp atmosphere in the attic and the fibre sleeper web warped; rails stayed straight though!  It wasn't flexible, though it was warpable... ISTR the rail was flat-bottomed, which might have accounted for a rigidity that was superior to the sleeper web

Edited March 6, 2023 by The Johnster

[DCB]

On 04/03/2023 at 14:10, Vecchio said:

considering a temperature range from 0 to 40 deg C your expansion from 0 to 40deg C would be approximately 0.8mm.

 

This is based on an expansion coefficient of 16.2 x 10E-6 m/deg C 

 

not very formula friendly this forum...

No way does my Peco Code 100 Steel in the shed or Nickle Silver in the garden comply with that formula, outside Track laid in the heat of summer with no gap ends up with the fishplates barely hanging on in winter and inside in a shed the track has shrunk between 2 and 3 mm since summer when it was butted up tight.     The formula I googled said 0.5mm per metre expansion over 40 degrees variation and the track above is anchored 1 metre to the left and 600mm to the right.  It's by a window but behind a blind which is always down.

Edited March 8, 2023 by DCB

[Vecchio]

Well I believe in physics.

[JeffP]

"Ye cannae change the laws of physics, Jim".

[matchmaker]

On 06/03/2023 at 11:23, Harlequin said:

Yes, Peco Code 75 PVA'ed to 3mm cork, 1440mm long sections of track with no expansion joints soldered to copper clad at each end which is screwed to the ply deck below.

 

Result in hot weather: The rails had nowhere to go and so they buckled sideways, undoing the PVA bond between the sleeper-base and the cork.

 

Experienced similar to this at Model Rail 2023 a couple of weekends back. Several fiddle yard tracks - Peco code 75 pinned to baseboard via cork  - buckled badly. It didn't happen on the scenic section of the layout as presumably the granite ballast held it in place. Once the layout was returned to base it settled back to normal in a few hours.

[BR60103]

I don't know what temperature difference would cause it, but a 1% change in a yard of rail is about 1/3".

If you have 2 yards straight tacked only at the outer ends, by applying Pythagoras the shift in the middle is about 3/4".

 

(Different opinions?)

 

[DCB]

I think people are underestimating the temperature variations, but the difference between N/S and Steel is quite dramatic in the formulas, 0,8mm / metre for 40 degrees, for N/S and 0.5 for steel, outside on track pinned to timber the oxidised track does not slide in the fishplates and breaks  the sleepers moving them 1 or 2mm longitudinally however reading about full size railways and in the hot summer sun their track gets much hotter than the air temperature and applying 80 degrees in the formula it starts to make sense, but it means constant hassle as ideally 450mm is about right for 1mm spaced rail joints at 20 degrees, for expansion and the least joints possible for electrical continuity.  Last month I had to swap out a straight because the gaps had become excessive and when I equalised everything to about a 1mm gap the end gap was too much for a fishplate so a piece a couple of mm longer had to be fitted.   

[Buhar]

That 450mm with 1mm gaps is helpful to me, extra droppers are not really a problem but cutting my track to that length means it'll fit in the suitcase for transport to Istanbul. Obviously there's the extra heat issue there as mentioned by other contributors.