Expansion Gap

[adeshers]

Hi to all,

Part of the track-base for my new garden railway has been laid but no track as yet. Would I be better off to leave it now until next spring and wait for warmer weather or can I lay it now and leave a suitable size expansion gap - if so what size gap do you think would be necessary? I'm using (mostly) LGB brass track. Anyone know the expansion co-efficient of brass? :thinking:

I will be soldering the joints to ensure electrical continuity. I intend to assemble several pieces in the workshop so that there will be only a few joints to solder on the ground. Has anybody done this and are there any pitfalls to avoid?

 

[Rhinochugger]

Coefficient of expansion of brass is not high.

But as Kim says, most people lay the track either loose, or occasionally fixed - every 10 foot or so, and I'm not aware of any expansion problems.

part of my line sits up on sleepers, and in some places the track is close to the edge - but it hasn't fallen off yet

 

[dutchelm]

The longest section on my line is over 50 ft. It is solid using Aristo screws or rail clamps. It is all laid in ballast & any expansion & contraction is lost in movement in the ballast. Its been down 10 years & I've never had an expansion problem.

 

[Rhinochugger]

Coefficient of expansion of brass is stated at .000019

Over 50 feet, the expansion is less than 1 mm - if you'll excuse the mixing of standards

 

[don9GLC]

<p>If I remember correctly even NASA lost a Mars probe due to mixing standards, so I tend to be wary of anything that quotes two different systems.</p><p> </p><p>According to my google search the expansion coefficient of brass is 18.7 (ten to the power -6) m/m K </p><p>[or measuring expansion in mm, 18.7 (ten to the power -3) mm / m K]</p><p>[1K (Kelvin) is 1 degree Celcius] </p><p> </p><p>For a 15 m length, and a temperature rise of 35 degrees (could be more in sunlight) the expansion would be 9.8175mm, nearly half an inch!</p><p>(18.7 / 1000 *15 * 35) </p><p> </p><p>Don't take a G scale train to Mars! </p><p> </p><p>Don
</p>

 

[spike]

Over 250 feet laid on ballast here, no discernable movement in any temperatures.
I do leave small gaps on most track joints but quite a bit of mine is clamped with
Hillmans and Splitjaws.

 

[Rhinochugger]

don9GLC - 19/11/2009 3:01 PM

<p>If I remember correctly even NASA lost a Mars probe due to mixing standards, so I tend to be wary of anything that quotes two different systems.</p><p> </p><p>According to my google search the expansion coefficient of brass is 18.7  (ten to the power -6) m/m K </p><p>[or measuring expansion in mm, 18.7 (ten to the power -3) mm / m K]</p><p>[1K (Kelvin) is 1 degree Celcius] </p><p> </p><p>For a 15 m length, and a temperature rise of 35 degrees (could be more in sunlight) the expansion would be 9.8175mm, nearly half an inch!</p><p>(18.7 / 1000 *15 * 35) </p><p> </p><p>Don't take a G scale train to Mars! </p><p> </p><p>Don
</p>

Yep, I was only quoting per degree Celsius, and it was a silly small amount.

even 10 mm over 15 metres is nothing for G Scale track to handle - it certainly wouldn't give the sort of problems that James May had with his Scalextric track at Brooklands

But that was the plastic expanding, not the metal - coefficient of explansion of plastic is humungus. At college (a few years ago !! ) they took a 1 metre length of plastic gutter, and filled it with water from a freshly boiled kettle - you could see the end creeping

 

[adeshers]

Thanks for the replies - I knew I would be given food for thought. I was intending soldering wires across the joints leaving the LGB fishplates in situ to provide mechanical alignment and securing the track to wooden inserts in the concrete/mortar trackbase, then applying loose ballast (alpine horticultural grit) over the top. From the combined wisdom I think I would have been securing the track at too close intervals so I will spread out the fixing points and leave the ballast to do the rest.

Perhaps a Stainz on Mars would've fared better than Beagle II

 

[KleineDicke]

Mind the Gap?

 

[johnsaintjim]

I agree with the calcs and agree completely that if you have track on ballast and don't fix it down, there is no need to be concerned about expansion in our climate. I believe in Australia or somwhere like Arizona and with fixed down track it is a different matter and best to take local advice.

My longest straight is Evensford Bank, about 12 metres and it sits and floats on the ballast very happily .

 

[Gizzy]

No expansion gaps here on this 15 m straight run.

Track is not fixed and floats on ballast.

The only thing I do, is fit the LGB 'dog bone joiners' on the curves, which stops the lateral movement....

 

[stockers]

adeshers - 19/11/2009 4:48 PM


a Stainz on Mars would've fared better than Beagle II

Its still running

 

[Geoff the garden nav]

2/3 of my track is lgb flexi track which floats in ballast, including a 15 metre long straight section, so far with no expansion problems, but then our garden and the long straight lengths of track run East West, the lgb track on the south side is sheltered by neighbors trees and shrubs. 1/3 is aristo mostly in 1500mm lengths, 20 metres of which is lightly pinned to 75 x 135mm timbers protected by mineral felt so far with no apparent problems on the Northern sunnyer side of the garden. On just a couple of days this summmer track in direct sunlight for a long time got almost to hot to touch! no buckelling apprent but the amount of foliage providing shade might be a factor in extreme movement on hot summer days.

My biggest problem is track fixed ridgedly to a conctret base with drymix greinte chippings/dust and cement across the top of the garden, massive, well 10mm, sideways displacment due to un even shrinkage of the clay soil by trees! results; rails bent side ways, fixings sheared off sleeper bases, gaps in rail joints and derailments.

 

[royale]

I laid most of my track in the winters - it includes Peco, LGB and Aristocraft. Except for the Aristo which bolts together, all the other track is only joined by rail joiners and much of it floats on ballast My longest straight is about 120 feet and that is screwed down to decking boards. I have never had a problem with track buckling due to heat expansion and I don't have to worry about electrical continuity. A couple of times a year, I give each joint a squirt of WD40. I run trains throughout the year, winter and summer. Very rarely when I need to change a rail joiner, I clean the rail ends with a Dremmel, use a small ammount of Copper-ease, tighten the joiner a little, and re-join the track - simples.

 

[Rhinochugger]

Agree with the garden navvy's findings. You are more likely to suffer from some form of ground movement that any problems with expansion.

It leads to a diffferent question about how substantial should the track base be?

:thinking:

For which I have a simple answer - as shallow as you can make it provided you bottom out on compact, undisturbed soil.

Today's Building Regs expect house foundations to be a minimum of 1 metre, and as much as 2 metres in some clay soils, in order to prevent heave from frost or changes in nearby trees. As it's unlikely that any one will want to dig down 1 metre for their railway, let alone 2 metres, make a good base on solid ground, lay the track in a floating method, and deal with a simple bit of re-levelling if the soil heaves badly enough.

Been my philosophy for patio construction as well - works every time

 

[Bram]

My track floats on the ballast, most of the track is Aristo so the joiners are screwed to the track with some LGB graphite grease added. No problems to date with expansion or conductivity

 

[stevelewis]

Yep .......................
Over 30+ years only ever laid in ballast, Relied soley on the railjoiners and when it became available in the 90s Graphite paste, never bonded track except for a few yards in 1976 which proved to be a total waste of time & effort.


My last line at old house lasted for 15 years until we moved with very few problems,

And incidentally my only source of track cleaning ever has been a block of wood & a sheeet of emery paper!!

 

[doverles]

my track is mixed LGB. PIKO. PEKO.ARISTOCRAFT its all screwed down on decking I used coffee stirrer to set the gap never had
a problem winter or summer
Les

 

[Geoff the garden nav]

See photos of what happened at the top of the garden, I decided to dig a narrow, 110mm wide trench , slightly wider than the LGB track bases by 125-150mm deep and filled it with concrete, the Idea being to give good support in this area for people and lawn mowers to cross. There are trees across the bottom of the garden, the problem occurred at the day work joint between the two sections it was constructed in! track fixed far too rigidly. I agree with Rhinochugger a minimal depth of excavation with track floating in ballast is best. The good thing about my experience is that the track bonding and joints with graphite grease have allowed the movement & prevented loss of continuity!

 

[Geoff the garden nav]

see photo