Hi folks, after some info / guidance please. My layout will include a viaduct but I'm having trouble researching what the trackbed would be, Would it be ballasted or concrete ? If concrete would the track have been laid on sleepers ? Thanks MalcT
It depends entirely on the type of viaduct. I have stone and brick arched viaducts, which will have ballasted track. There are also some steel bridges, on which I can have a few different treatments. The major plate steel girder bridge also has ballasted track, but the others with trusses or girders underneath and more open structures will get steel or wooden girders or baulks ... if I ever get around to that detail. Best advice is to find photos of the style of viaduct you wish to model, and go with that for how the track is treated. Look at a few cab ride videos on YouTube or DVD to get some ideas.
If you are planning to model a traditional British masonry viaduct then the trackbed would be ballast laid, the substrate beneath the foundation ballast would consist of an arced masonry lining incorporating drainage gullies on each side diverting drainage water out through sluices down the viaduct piers. Obviously for us modelers such detail always goes unseen but as for a precast concrete pad which directly supports trackwork that may well be the case with hi-tec structures designed for ultra high speed transport systems on the Continent or Japan.
If I was doing a viaduct I would model this one. https://en.wikipedia.org/wiki/Glenfinnan_Viaduct#/media/File:Glenfinnan_Viaduct.jpg Made famous by the Harry Potter movies.
Glenfinnan viaduct was the very first concrete structure in the UK, McAlpines were chosen for their skills in using concrete to create mass structures, this was backed up by the fact that the local Scottish stone called "schist" was almost too difficult to work with as a building material. Glenfinnan viaduct still has the same trackbed foundation underlay as a masonry viaduct and the track is top dressed with ballast in the conventional way.
Ahhh Schist ... a mediun grade metamorphic rock, that would have started life as mud / silt, then via compression and time would become the sedimentary rock Shale. Futher compression, & time they would become a low grade regional metamorphic rock Slate then Phyllites. Now add in some volcanic or mountain building activity and the rocks start to crystalise and align and become Schists. If you go a bit further, just before they would melt and become an igneous they become Gneises. See it's not just model railways I can blether about. Whats more worrying, is the last time I did any Geology was 42 years ago, and I can remember that, I just wish I could remember where I put my glasses this morning Paul
Great explanation there Dundee... I knew if I talked about such a subject it would prompt a more consistent answer , so folks the moral of the story is if you are thinking of building viaducts then avoid making them from "schist" at all cost as they won't stand the fullness of time otherwise.
