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topic: 1746Track relaying
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posted: 22 Dec 2011 19:40

from:

Phil O
 
Plymouth - United Kingdom

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Hi All

Here are a couple of clips of track relaying machines in action, sorry they are only available in 304.8mm to the foot scale and for plain track only.

Part 1: http://www.youtube.com/watch?v=iF-3ditSCIk&feature=related
Part 2: http://www.youtube.com/watch?v=ixfIOr6eycU&feature=related










Cheers

Phil


posted: 23 Dec 2011 09:14

from:

its_all_downhill
 
North Yorkshire - United Kingdom

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Hi Phil,

Fascinating stuff thanks for that find..

Regards
Tom

posted: 23 Dec 2011 13:09

from:

LSWRArt
 
Antibes - France

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hi Phil

Interesting videos.

A question - I had always thought that the rail had to be pre-stretched to allow for expansion and contraction, but this was not mentioned in the video. 
Without this, when the rail expands in the summer, I would have thought it would have pushed the whole curve outwards.  Or is the ballast strong enough to hold the expanding steel?
Or, if the steel is pre-stretched, how is this done?
I always remember when I was about 15, I was building my first track, soldered to rivets for a dock railway (no sleepers, so nice and simple).   The layout was in a greenhouse and coming back next day I found almost every solder joint had been ripped apart. 
Nothing like doing something and getting it wrong to teach you a lesson.   :shock:
Regards,
Arthur

posted: 23 Dec 2011 18:34

from:

R A Watson
 
 

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Arthur,

There used to be a procedure where the rail was "tensioned" either by heating (an early and soon discontinued practice) or stretching using hydraulic tenioners, after the rail had been restrained by the clips expansion was limited to just a a few feet at either end of the rail length.

With the introduction of even heavier rail section and sleepers this practice has been virtually discontinued as the mass of the structure stops linear movement and the rail expands sideways! (ie. thickens, not moves), to further assist, extra ballast is piled on the sleeper ends giving the familiar mound down each side of the modern track.
Last edited on 23 Dec 2011 18:36 by R A Watson
posted: 23 Dec 2011 19:30

from:

Nigel Brown
 
 

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R A Watson wrote:
With the introduction of even heavier rail section and sleepers this practice has been virtually discontinued as the mass of the structure stops linear movement and the rail expands sideways! (ie. thickens, not moves), to further assist, extra ballast is piled on the sleeper ends giving the familiar mound down each side of the modern track.

Interesting. I suppose in theory this could result in gauge narrowing. When the rail contracts, is there a risk of fracture?

Cheers
Nigel

posted: 23 Dec 2011 20:17

from:

R A Watson
 
 

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Nigel,

The lateral expansion is only for the equivalent amount relating to the bit of rail between the two adjacent fastenings and therefore is miniscule. This is fully acceptable and does not cause any concern for the designers being only to many 00's of a decimal point.

Wally



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