[Oz the Dog]

Just returning to railway modelling after a short gap of about 45 years. Hence a few knowledge deficiencies that are being filled by MRF.

I am laying Peco streamline on 3mm cork this winter on a loft layout. It occurred to me that if the track joins are tight at current temperatures - say 5-10 degrees C then in the summer the nickel silver will expand and maybe cause track to buckle. This would be avoided by leaving expansion gaps at track joins.

Can anyone comment whether this is likely to be a problem and if so what is the recommended gap to be left at joints.

I am insulating the roof over the layout to minimise temperature fluctuations but they cannot be avoided.

Thanks

Keith

 

[Richard Johnson]

**Yes you are right but expansion and contaction will be more from timber movement than rail (wood moves much more than nickel silver).

Paint or seal all baseboard timber on all surfaces.

reason:

* when its hot, wood dries and shrinks - at the same time, the rail expands a little.
* When its damp and cold, wood expands and nickel silver rail shrinks.

If you are laying track in winter, then regular gaps should be about 1mm.

After sealing the timber, the next best additional protection is air conditioning for humidity/heat control but thats possibly a little exteme - as a substitute a fan heater on a timer in winter - set it to run on heat for say an hour two or three times a day to keep humidity minimised and on fan only in summer to keep air flowing to keep things cooler (hot air gathers in the roof space).

Also if you can, a light plastic sheet over the layout between uses will minimise any condensation / moisture in winter and dust on the layout in summer.

Richard

 

[80class]

Hi Keith and welcome to the forum.

Quick reletaed question, all my baseboards are sundeala (very well supported!). Would you recommend painting those too Richard? I had been told not to paint the underside, but I can't remember why, It may have had something to do with sound.

Thanks,

Rob

 

[Richard Johnson]

*** Hi Rob

Sundeala is more related to cardboard than wood in a way, but I'd think it was as prone to movement as any form of similar cellular product.

I certainly have no idea why you should leave one side unpainted - it sound a little like an "urban myth" like so many similar comments.

I'd have thought that logically, with both sides covered/sealed stresses would be evened out and sealing would increase not decrease stability. A coat of paint or sealer would have no effect on noise.

Richard

 

[80class]

Yes I had thought that with regards to the surface stresses. Funny how many poorly informed urban myths surround our hobby!

Thanks for clearing that up,

Rob

 

[Twiglet]

I have been told (by this Forum) to leave about 0.5mm gap per metre of track if you are coping with big temperature changes. I have tightened my trackwork up a bit since getting the loft properly insulated (in the eaves) - which has reduced winter-summer temperature differnces by a factor of at least 2. As to painting baseboards, again I have heeded advice, although I can't say my pine+sundeala/MDF efforts have moved much in the few years they have been up there. I reckon, for what it is worth, that the problem will be MUCH worse in a damp outside shed than anywhere else.

 

[Richard Johnson]

*** Hi Mike - the 1/2mm is quite true as an average - I suggested the 1mm as in UK its mid winter, with max dampness in the wood and coldest state of the rail. It may be OK to be less if the conditions are controlled or the area is heated, but there was no indication of that. (Likewise if the rail is laid in mid summer like it is here when wood is shrunk back and rail at max expansion, I'd probably have recommended far less).

Richard

 

[Twiglet]

Many thanks Richard ... I read with some envy about our American (and Australian?) friends who do not have this problem - thanks to aircon they can simply solder the lot and not worry about thermal expansion/contraction at all.
In general terms though, which is more of a problem - humidity changes or temperature changes?

 

[Brian Considine]

It's not a problem in the UK to insulate & control temperature/humidity - it's just that it can cost a great deal of reddies to do so.

 

[Twiglet]

Brian, you are quite right - if you can put aircon in a US home you can put it in a UK one too; the problem is that firstly so few homes in this country have any form of proper climate control fitted as standard and, secondly, there is so little demand that prices are sky-high even if you wish to install it. Just a generation ago even central heating was quite rare ... I remember frost on the inside of the windows!

 

[dwb]

QUOTE I remember frost on the inside of the windows!

Only once in my experience - 1983, The Angel Inn, Market Harborough. I grew up on the coast. Low overnight temperatures inland were something of a shock to me.

David

 

[Richard Johnson]

*** Hi Mike

DOn't believe all the rumours - many AU modellers have nice environments, but there are just as many "shed" layouts here as in UK.

which is more of a problem - humidity changes or temperature changes?

It depends on the extremes-- for example, if I had a layout in a shed here, the outside temperature may be say 35 degrees c but at the layout point where the afternoon sun shone in a window, it could be 50, 60c or more.... In that case, locally, heat would be the issue.

However, I think its always a combination: Summer is hot and things dry out when its hot. Winter may or may not be all that wet but it follows autumn when rain is generally high, so cold and damp happen together too... Impossible to separate them as "layout environmental issues" really

regards

Richard

QUOTE (Mike H. @ 21 Jan 2009, 16:43) <{POST_SNAPBACK}>Many thanks Richard ... I read with some envy about our American (and Australian?) friends who do not have this problem - thanks to aircon they can simply solder the lot and not worry about thermal expansion/contraction at all.
In general terms though, which is more of a problem - humidity changes or temperature changes?