Ballasted decks on metal bridges.

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drmditch
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Ballasted decks on metal bridges.

Post by drmditch » Thu Mar 01, 2018 5:10 pm

Please does anyone have any information about metal bridges having ballasted decks?

Preferably on the LNER, North Eastern Area, prior to 1948.

I am basing a model on Langley Moor Viaduct on the ECML, (otherwise known as the Deerness or Dearness Viaduct, but not the now-demolished one on the Durham Bishop Auckland line.) I think that it is now has ballasted track, but I suspect it would not have originally built that way.

This model is/will be exposed to full sunlight for much of the day (when it stops snowing!), so it has to be UV and heat stable.
The deck is actually 1/2" birch ply which is fairly strong. It is nearly 4' long. If I make track using Code 100 rail and PCB it may not have enough flexibility to cope with heat expansion. If I use my normal 'old and clunky' Peco Code 100 and allow sufficient expansion gaps then it will probably cope.

I did raise a thread ... here... a while ago
There is an account of it's recent re-furbishment ...here...

All information and (sensible) advice will be gratefully received!

PinzaC55
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Re: Ballasted decks on metal bridges.

Post by PinzaC55 » Thu Mar 01, 2018 11:13 pm

A majority of bridges would have waybeams (longitudinal sleepers). The obvious problem with ballasted track on a bridge is that it is heavy and retains water which promotes rust.
This is a decent site for photos.

http://www.forgottenrelics.co.uk/bridge ... index.html

John Palmer
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Re: Ballasted decks on metal bridges.

Post by John Palmer » Fri Mar 02, 2018 2:05 am

The Scalefour Society has produced a useful DVD titled 'A Modeller's Guide to Civil Engineering Structures' by John A Smith, which contains some details of how ballasted decks are arranged. Basically, such a bridge involves a trough that carries the ballast and rail panels and is borne upon the lower flanges of the main girders of the bridge that flank the trough on either side. This main trough is constructed from a series of subordinate, transverse troughs that form a castellated cross section. Drainage of the formation is promoted by drain holes cut into the bases of these transverse troughs. Hope this rather clunky description helps to provide some explanation of the constructional approach adopted; much easier to appreciate from a drawing!

drmditch
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Re: Ballasted decks on metal bridges.

Post by drmditch » Sun Mar 04, 2018 12:45 pm

PinzaC55 wrote:
Thu Mar 01, 2018 11:13 pm
A majority of bridges would have waybeams (longitudinal sleepers). The obvious problem with ballasted track on a bridge is that it is heavy and retains water which promotes rust.
Exactly! My problem is that this bridge is just inside double-glazed garden doors which face due south.

I have worked out a design using strips of PCB about 8" long with NS rail spot soldered to simulate chairs, and track joiners with sensible expansion gaps. I still worry however about the difference in expansion between the PCB and the rail.

It may be better to emulate the NER and add additional under-girders into the design to support the (fictional) weight of the trough girder (thank you Mr Palmer) and ballast.

Hatfield Shed
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Re: Ballasted decks on metal bridges.

Post by Hatfield Shed » Sun Mar 04, 2018 6:54 pm

drmditch wrote:
Sun Mar 04, 2018 12:45 pm
...My problem is that this bridge is just inside double-glazed garden doors which face due south. I have worked out a design using strips of PCB about 8" long with NS rail spot soldered to simulate chairs, and track joiners with sensible expansion gaps. I still worry however about the difference in expansion between the PCB and the rail...
I would be inclined to trial the proposed construction by making up a length over a couple of the 8" PCB strips, and heating it. I would suggest allowing 70C for the solar gain worst case. 'Painting' the length with a hot air gun or hairdryer will do the job. If there is readily visible deflection from straight when sighting along the length then it's no go

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Blink Bonny
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Re: Ballasted decks on metal bridges.

Post by Blink Bonny » Fri Mar 09, 2018 1:47 am

Ay up!

Would putting bullhead rail in white metal chairs work? The rail would be free to expand and the chairs could be soldered to the PCB?
If I ain't here, I'm in Bilston, scoffing decent chips at last!!!!

drmditch
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Re: Ballasted decks on metal bridges.

Post by drmditch » Wed Mar 28, 2018 7:29 pm

In regard to Langley Moor Viaduct on the ECML (sometimes referred to as the Deerness/Dearness Viaduct - but not to be confused the the viaduct on the Bishop Auckland line), I have found the following information.

Tomlinson p.659 (mine is the David and Charles 1967 reprint) says that both the Croxdale and Langley Moor viaducts used lattice-girder construction when built circa 1871-2.
There is a picture on p.542 of the original wooden viaduct on the Leamside- Bishop Auckland line. The view is looking east, and in the background some detail can be made out of a girder bridge on the Tursdale - Relly Mill diversion, perhaps still under construction.

The NER Line Diagram published by NERA, shows the Croxdale Viaduct as brick (which indeed it still is). The same Line Diagram has a convenient little sketch of the Langley Moor viaduct. It mentions:-
W.I outside girders
Steel inside girders
Steel Decking covered with stone metalling.

So two questions:-
1. When was the Croxdale viaduct replaced (or was Tomlinson wrong?)
2. When was the Wrought Iron construction at Langley Moor strengthened, and was the Decking replaced by the LNER or BR
(I think the Line Diagrams were kept up-to-date by both organisations.)

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