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Author Topic: Track Expansion/contraction  (Read 2448 times)

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Offline kirky

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Track Expansion/contraction
« on: November 30, 2011, 07:18:23 PM »
I wonder if anyone has any data on peco code 55 track expansion/contraction?

What I'm after is some idea of how much a length of track (eg a full length of flexi-track) changes over given temperatures. For instance how long would would the track be at say 5 degrees C and how long would it be at 30 degrees C, (which I'm guessing would be the extreme temperatures our railway would have to endure)
This is so I can work out how much of gap we will need to leave between the track pieces on our Northallerton project herehttp://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.0.

Cheers
Kirky
Northallerton will make its next public appearance sometime after LOCKDOWN

Layout: Northallerton: http://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.msg16930#msg16930

www.northallertonngauge.co.uk

Cleveland Model Railway club website: www.clevelandmrc.club

Offline Bikeracer

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Re: Track Expansion/contraction
« Reply #1 on: November 30, 2011, 07:32:25 PM »
Found this,dunno if it helps....
One inch of steel will expand 0.00000645 inches for every degree Fahrenheit increase in temperature.

Basically if my maths are right,100 inches will grow about 0.0007" for each Fahrenheit degree of temperature rise.

Just google expansion of steel.

Allan
« Last Edit: November 30, 2011, 07:38:41 PM by Bikeracer »
I'm not a complete idiot..some bits are missing.

Offline Rheneas N Gauge

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Re: Track Expansion/contraction
« Reply #2 on: November 30, 2011, 08:08:19 PM »
well Do Not glue down track with soldered joins in very warm temperatures as the rails will buckle, the maximum gap for contraction is about 2mm and around the same for expansion but it all depends on the track layout and its fixings, if its on a curve 4 radius or with a lot of pins the rails will move outwards or inwards temperature permitting but if there are only a few the track without fixings with move to the inside of the curve or outside, when laying the track butt up approximatly half of the rails, if its a big layout leave a 1mm gap every 6 foot but all the rails connecting to points MUST be touching fully and have maybe 2 extra fixxings to prevent the rails moving away during contraction,
if I can think of anything else i'll let you know

Offline EtchedPixels

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Re: Track Expansion/contraction
« Reply #3 on: November 30, 2011, 11:37:23 PM »
For most cases the problem isn't the track expanding - which is a tiny tiny amount but the fact that wood shrinks as it loses moisture when it gets warm.

"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline kirky

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Re: Track Expansion/contraction
« Reply #4 on: December 01, 2011, 12:38:07 AM »
For most cases the problem isn't the track expanding - which is a tiny tiny amount but the fact that wood shrinks as it loses moisture when it gets warm.

Thanks guys for the replies. I think you might have a point here EP.
One of the reasons I'm concerned about this whole problem, is that our OO guag layout in the club suffered major twisting in the fiddle yard, in the summer. But given that we had just moved from our old club rooms (which was wetter than a wet weekend in Wetsville) then the problems that layout encounteed may not be that apparent onj ours. Our boards were buil in the summer, and even though it now significantly cooler, the boards seem to be fairly stable. The new rooms are very dry and we used ply almost throught, which we have treated.

Cheers
Kirky
Northallerton will make its next public appearance sometime after LOCKDOWN

Layout: Northallerton: http://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.msg16930#msg16930

www.northallertonngauge.co.uk

Cleveland Model Railway club website: www.clevelandmrc.club

Offline Chinahand

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Re: Track Expansion/contraction
« Reply #5 on: December 01, 2011, 06:09:54 AM »
All of which reinforces the case for varnishing/sealing all baseboard materials, including the edges, before laying track.
Regards,
Trevor (aka Chinahand)
(Sorry, but you are not allowed to access the gallery)

Offline poliss

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Re: Track Expansion/contraction
« Reply #6 on: December 01, 2011, 12:33:47 PM »
The varnish should be water based, which will allow the wood to breathe, and not polyurethane varnish.

Offline EtchedPixels

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Re: Track Expansion/contraction
« Reply #7 on: December 01, 2011, 02:37:13 PM »
One of the reasons I'm concerned about this whole problem, is that our OO guag layout in the club suffered major twisting in the fiddle yard, in the summer

This is one reason I like to use ply top and also strips underneath. It means the board cannot bow so easily as its a box girder and for the timber to curve it must also stretch the ply top or bottom.

It would be very interesting to know how people building foamcore baseboards and the like find the expansion/contraction behaviour - presumably it is a good deal more dimensionally stable ?
"Knowledge has no value or use for the solitary owner: to be enjoyed it must be communicated" -- Charles Pratt, 1st Earl Camden

Offline Flakmunky

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Re: Track Expansion/contraction
« Reply #8 on: December 01, 2011, 03:12:00 PM »
Personally, I got really paranoid about this when I first started out... But came to the conclusion that as my layout is housed indoors and not in a garage, loft, basement or shed then as long as my timber was acclimatised properly prior to building the baseboards then the risk of warping would be very low. Also, as the temperature in my house is fairly constant then expansion would likewise be a very low risk...

EP - I would concur with your hypothesis but have no empirical evidence to support it!

Offline Chinahand

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Re: Track Expansion/contraction
« Reply #9 on: December 01, 2011, 04:13:08 PM »
The varnish is not to reduce expansion and contraction. It is to maintain the moisture content of the wood at a constant level. Wood will always expand and contract due to temperature changes, no matter what you do to it, but it is the increase/decrease in moisture content that has the biggest effect on wood.

For this reason I'm afraid I must disagree with poliss and say that the varnish should be polyurethane or yacht varnish as this seals in whatever moisture is still present after acclimatising the wood to the room.
Regards,
Trevor (aka Chinahand)
(Sorry, but you are not allowed to access the gallery)

Offline kirky

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Re: Track Expansion/contraction
« Reply #10 on: July 19, 2013, 09:35:49 PM »
I wonder if anyone has any data on peco code 55 track expansion/contraction?

What I'm after is some idea of how much a length of track (eg a full length of flexi-track) changes over given temperatures. For instance how long would would the track be at say 5 degrees C and how long would it be at 30 degrees C, (which I'm guessing would be the extreme temperatures our railway would have to endure)
This is so I can work out how much of gap we will need to leave between the track pieces on our Northallerton project herehttp://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.0.

Cheers
Kirky


Well I thought I'd better bump this topic given the mild conditions we're enjoying at the moment!
I remembered to take a thermometer with me to the club yesterday. The shade temperature got up to 31.5 degrees Celsius, whilst in the sunshine the temperature was over 45!. So much for my prediction of 30 degrees. At the moment here isn't much we can do about shading the windows as they are twenty feet up and there's a big dublo thing in the way.
Needless to say, despite painted and protected timber, track has definitely expanded in the Warm weather. I would guess a full length of code 55 is maybe 2 mm longer, but I've not checked that yet.

Cheers
Kirky
Northallerton will make its next public appearance sometime after LOCKDOWN

Layout: Northallerton: http://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.msg16930#msg16930

www.northallertonngauge.co.uk

Cleveland Model Railway club website: www.clevelandmrc.club

Offline Chinahand

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Re: Track Expansion/contraction
« Reply #11 on: July 19, 2013, 11:50:32 PM »
Have you checked to make sure it's not the baseboards shrinking as the moisture dries out of it ?

The formula for the coefficient of thermal expanson for nickel-silver is c = 9 * 10^(-6) in/in/degree F
or for a 36" length of track c = 9 x 0.000001 x 36 in/in/degree F

So for a rise of 25 degrees F (say from 60° F (15.5° C) to 85° F (29° C) a 36 inch length of track will increase by 0.0081 inches or 0.21 mm. That's 1/5th of a millimetre which is not a lot. I suspect your problem lies with the boards rather than the track.
Regards,
Trevor (aka Chinahand)
(Sorry, but you are not allowed to access the gallery)

Offline kirky

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Re: Track Expansion/contraction
« Reply #12 on: July 20, 2013, 07:58:32 AM »
Thanks for that Trevor.
However, I think we are suffering rather larger temperature fluctuations than you have quoted. As I mentioned, the other day it was 45 Celsius, that's 115 F, near enough. At the bottom end it undoubtedly gets cold as we have no heating. I would go so far as to say it gets down to 5 Celsius or 41 F. That's a temperature difference of nearly 75 F. And unfortunately, a lot of the track was laid when it was cold.
So using your formula that's going to be nearer 3/5 mm expansion per length, which is enough to cause problems. And given that our boards are 1500 mm long, the effect is multiplied along the boards, and tracks on the fiddle yard with tight joints are the ones that have moved, not the ones with looser connections.
I would of course agree that these temperatures will have an effect on the boards. But the boards are built almost entirely of treated plywood. (Incidentally, plywood that is too cheap for its own good in some respects as it has gapped between its veneers at some of the board ends, thus creating a space below where the tracks butt up to each other, and causing alignment issues.)
Thanks for your help in this, much appreciated.
Cheers
Kirky
Northallerton will make its next public appearance sometime after LOCKDOWN

Layout: Northallerton: http://www.ngaugeforum.co.uk/SMFN/index.php?topic=1671.msg16930#msg16930

www.northallertonngauge.co.uk

Cleveland Model Railway club website: www.clevelandmrc.club

Online msr

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Re: Track Expansion/contraction
« Reply #13 on: July 20, 2013, 10:57:57 AM »
Another aspect is the effect of direct sunlight on the track. My layout is in an insulated loft and usually protected from the worst excesses of the sun by having the blinds on the Velux windows pulled shut. Nevertheless the far track lifted yesterday at one point (see photo), the reason being that I opened the window which is just above this shot and this allowed the sun to shine directly on the track. It was only a chink, and for only a few minutes, but sufficient to heat up the rails causing them to lift off the plastic base (Peco Code 55), which remained firmly pinned in place.

Moral of the story: don't let the sun shine directly on the rails!

Mike

Offline daveg

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Re: Track Expansion/contraction
« Reply #14 on: July 20, 2013, 11:17:01 AM »
The current (UK) weather conditions must be a challenge to many who have layouts in sheds, lofts, etc.

Expanding track is a major problem but there’s also the general advice to avoid locos, rolling stock and scenic materials, especially card mounted printed buildings, being left in direct sunlight for too long.

My layout is currently in store with all stock and buildings packed away. Nevertheless, it’s all in a room with the blinds 90% closed to reduce the chances of the sun doing any damage.

Dave G

 

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