Embankments? building? “Oh come!” I can hear you cry, what’s difficult about that?
Well, to be fair, creating the actual embankment is relatively simple for anyone with a modicum of model making and track laying experience but I will cover it shortly just in case.
No, the challenge with embankments isn’t the raised track bed itself but the surrounding landscape.
Let me explain.
Trains run best on track that’s level, even a slight drop or incline is a challenge for a locomotive pulling hundreds of tons of freight or passengers. The illustrious James May, of Top Gear fame, has even done a programme on this:
Unfortunately for us landscape isn’t flat. Far from it. On the trains from Guilford to Ally Pally for the recent London Festival of Railway Modelling, for example, I counted no less than 17 points where my trains rose up above the surroundings.
So railway engineers devised embankments, along with cuttings, tunnels and viaduct, as a way to create a level roadbed on which the track can sit even while the ground around it rises and falls.
And there are lots of these embankments across the country. So many that between 1834 and 1841 — the boom years of railway building in the England — nearly 100 MILLION tons of ground was excavated for their construction*.
All this soil and rock just to keep the track level as the landscape through which the track travels rises and falls!
And this takes us neatly to the challenge of creating realistic embankments.
To have credible embankments on a layout the model landscape needs to be lower than other areas through which the track runs — creating the need for the embankment.
On the typical base board this creates a problem because the boards, by design, are all flat.
There are two solutions.
Firstly, cut into the baseboard to create lower terrain on which the embanked track can rise up.
Frankly, this is a lot of work. It can be done — if you have deep enough baseboard —but it’s still hard work to chisel and carve out sections of the surface.
Instead my preferred technique is to raise up the other parts of the layout. This then becomes the new ground level with the underlying, baseboard becoming the lowland across which an embankment can run.
To do this I glue polystyrene sheets across my baseboard into which I can then easily cut hollows.
(It also has the advantage that channels for rivers and streams can be easily made).
Extra: There is another approach which is really beyond the scope of this article. Namely, building roadbed and landscape between joists. This doesn’t have a flat surface, instead strips of plywood (or similar) held by supports from the sides or below, form a ‘floating’ track bed. Between these hang a matrix of cardboard strips on which further material is added to make the ground surface.
This techniques has the huge advantage that the ground running around the track can rise and fall as you want. It is however far more time consuming to make.
How To Make Embankments
As said above, I lay sheets of polystyrene on my baseboard, lay the track on this and then cut into this either side of the track when I want the surrounding landscape to be lower.
This ensures the track remains level across the layout.
The shoulders are then carved to slope at a slight angle. As mentioned above, embankments are made from ground material (usually excavated from nearby) pilled up so the angle needs to be a balance of being steep enough to climb to height required for the track but stable and not fall — known as the angle of natural repose.
The consensus seems to be that angles of between 15 and 50 degrees are appropriate with nearly vertical slopes for rock to a 1 in 3 gradient for clays*. (If you’re concerned about realism. If not I’d suggest embankments slopped at around 25 degrees). On the section of my layout I’m currently working on for example part of the track I want to embank runs through a depression surrounded by hills. Given the setting (set in Cornwall, around St Austell and leading up to Bodmin) the prototype embankments would most likely have been made from the rock of these hills and so a steep angle can be justified.
With the embankment sides shaped, paint them a dark colour to match the nearby terrain and then cover with a soil texture colour scatter and finally ballast the top and between the sleepers.
If the embankment is tall or runs across watery landscape a culvert through the embankment maybe appropriate as an added detail.
So there you go, you were right. Embankments aren’t difficult but hopefully I’ve answered any questions you have about them and motivated you to build them on your layouts.
- University of Cambridge
- Practical Railway Engineering, Clifford F. Bonnett
Picture: A class 37 makes its way over an embankment on the wonderful Rannoch Moor N gauge layout, seen at the 2017 London Festival of Railway Modelling. Photo (c) Model Railway Engineer.