Bridge Trackbed

[Newbie2020]

Hope this  is in the right section! As part of the Lyneworth to Millhampton branchline crosses over the central well of the layout I have decided I want a Bowstring Bridge to achieve this. The question is, would the track bed across the bridge be ballasted? or finished in some other way. I can find lots of pictures of Bowstring type bridges but none that show the trackbed clearly.

 

Over to the "Hive Mind" !!

 

Cheers

 

Clive

[Michael Hodgson]

I would expect the running rails to be supported by and secured not to sleepers but on longitudinal baulks (way-beams) which in turn would be supported by transverse girders. 

 

The purpose of ballast on ordinary track is to act as a bed supporting sleepers and constraining their movement whilst allowing drainage.  These functions are not appropriate to a bridge, so I wouldn't expect it to be ballasted.  It could be open between the girders, although this would present a hazard to workers on the track so there might well be some sort of infill decking as a  safety precaution.

[Rivercider]

I think this bridge at Stapleton Road Bristol is a bowstring bridge, since replaced when the four tracks here were re-instated.

45007 heads south 30/9/81

 

cheers

[fulton]

Could be open deck, rail supported on timber baulks, or closed deck, with normal ballasting. The bridge for my new layout is open deck, which is prototypical for my location, I think also makes a more interesting model.

[Newbie2020]

Thanks guys!

[doilum]

The swing bridge at Selby and it's approach bridges were plated steel.

[eastglosmog]

Nuneham bridge is rather famous at the moment.  It is a bowstring bridge and has ballast in a trough. https://en.wikipedia.org/wiki/Nuneham_Railway_Bridge

[Wheatley]

Many waybeamed bridges were altered over the years to ballasted troughs. Waybeams hold the track rigid which can cause issues where it meets the more flexible ballasted track either side. About 20 years ago one of my responsibilities was keeping a list up to date of locations where trolley staff on TPE services were not to serve coffee because waybeamed bridges caused a kick which was throwing it all over passengers when the steward(ess) got knocked off balance. Batley was one (station subway), and somewhere near Church & Oswaldtwistle. Church caused a major industry kerfuffle when the legendary Stuart Baker, then Ops Director at RRNE imposed a 'Company Speed Restriction' over the bridge because Railtrack wouldn't impose a TSR for condition of track.  

 

A botched conversion from waybeamed to ballasted trough caused the collapse of the bridge at Stewarton a few years ago, the LMS had boxed in the side girders in the 1930s and created a sealed void which was impossible to inspect. The beautifully painted but paper thin girders folded up under a freight train.  

[iands]

Some photos of mine whilst on official business, hope they are of some use.

 

Although a swing bridge not a Bow String bridge, the photos show Longitudinal way beams (on the moving part of the bridge) and the transition to ballasted track: Somerleyton.

(Apologies for the quality of the images - cheap cameras provided by Railtrack).

 

 

 

Similarly at Goole.

 

 

 

 

And two still taken from a cab ride video taken whilst I was working on the East London Line project. The bridge at Haggerston shows ballasted track, whilst a little further along the Bow String bridge at Shoreditch High Street the modern use of 'slab track' was used.

Haggerston Bridge S-B.docxShoreditch S-B.docx

[Compound2632]

5 hours ago, Wheatley said:

A botched conversion from waybeamed to ballasted trough caused the collapse of the bridge at Stewarton a few years ago, the LMS had boxed in the side girders in the 1930s and created a sealed void which was impossible to inspect. The beautifully painted but paper thin girders folded up under a freight train.  

 

That sent me off to look up the RAIB Report. A key factor would appear to have been the lack of a good drawing.

[Wheatley]

Thanks for that, I've got that saved somewhere but I've clearly mis-remembered the beauty of the painting on the girders !  

[Tom Burnham]

It was replacing the timber baulks beneath the rails of the River Beult bridge between Headcorn and Staplehurst that was the cause of the well known accident on the SER in 1865.

[Artless Bodger]

The Medway bridge at Maidstone East (locally aka 'high level bridge') is now a truss, it was a bowstring until upgraded (for boat train traffic in the 20s I think - pictures in Maidstone museum show the bowstring with SECR tank engine). It has ballasted track, but this is to accomodate the pointwork on the bridge - prior to the changes for Eurostar diversions there was a trailing crossover, incorporating a double slip in the down line leading into the down bay and goods yard.

 

This bridge was my 'prototype for everything' for occasions at club where the question of ballast on girder bridges was raised.

[Tom Burnham]

21 hours ago, Artless Bodger said:

The Medway bridge at Maidstone East (locally aka 'high level bridge') is now a truss, it was a bowstring until upgraded (for boat train traffic in the 20s I think - pictures in Maidstone museum show the bowstring with SECR tank engine). It has ballasted track, but this is to accomodate the pointwork on the bridge - prior to the changes for Eurostar diversions there was a trailing crossover, incorporating a double slip in the down line leading into the down bay and goods yard.

 

This bridge was my 'prototype for everything' for occasions at club where the question of ballast on girder bridges was raised.

High level bridge rebuild was completed in Dec 1927 or thereabouts.  It's just occurred to me that River class locos (K and K1) were running via Maidstone East before then.

[2251]

On 20/04/2023 at 11:13, Wheatley said:

Many waybeamed bridges were altered over the years to ballasted troughs. 

 

Indeed.

 

There are some very clear photos here showing a formerly waybeam bridge converted to ballast under repair:

 

http://bridgestobroadway.blogspot.com/

 

What appear to be small square riveted patches riveted on at regular intervals are the remains of the steelwork that used to hold the waybeams in place. 

[Newbie2020]

Thanks everyone, some fantastic and fascinating answers!

 

Cheers

 

Clive