Thursday, June 06, 2019

How I constructed a stone embankment from cast concrete

Having made a rake of Snailbeach style hopper wagons (see How I constructed a rake of Snailbeach hopper wagons - pending) and a set of loading hoppers (see How I constructed some loading hoppers from foamboard - pending) for the sand quarry siding, I realised that I needed to find some way for the loading hoppers to be filled theoretically with sand. For a while, I toyed with the idea of constructing conveyor belts or mechanical shovels, but these seemed to be beyond my somewhat limited constructional capabilities so, in the end, I opted for stone embankment behind the hoppers by which means 2' narrow gauge wagons could discharge directly into the hoppers.

The civil engineering aspect of garden railway modelling has always been of great interest to me, particularly working with concrete which seems to me to be an ideal medium for creating durable structures in the garden environment. Having already cast some overbridges (see How I cast some overbridges in concrete), station platforms (see How I cast concrete platforms) and loading banks (see How I cast a loading bank and How I cast loading docks), I felt I was up to the challenge of creating an embankment from cast concrete.

Firstly, I needed to measure up and prepare the site. This entailed uprooting some of the foliage and checking clearances for the loading hoppers.

I then dug foundations for the embankment, using a small trowel. As the embankment wasn't going to be bearing any appreciable weight, the foundations only needed to be around six inches (150mm) in depth.

I then made some shuttering from off-cuts of tongue and groove weatherboard which I had rescued from the set of my local amateur drama society following their staging of a play featuring three beach huts. I could have used plywood, but didn't have any off-cuts to hand.

The shuttering was roughly shaped to follow the contours of the existing rocks. Stonework courses were then marked on the inside of the shuttering.

A hot glue gun was then used to accentuate the mortar courses, thereby creating a mould for the concrete.

As the stonework was going to be 'undressed', the courses and stone blocks were fairly random in size and orientation.

The shuttering was then put into place and held firm with some bracing made from timber wedged against the rails or adjacent rock faces. At this point, I decided to remove a small fir tree which was going to be difficult for the track to circumnavigate. This revealed a delicate miniature rhododendron which had been swamped by its faster growing neighbour. I decided the rhododendron is a far more attractive plant for this spot.

A one inch layer of crushed rubble was put into the bottom of the shuttering, as much to save mixing more concrete as to act as a foundation. A 3:1 mix of builders' sand and cement was made, to which was added a couple of shakes of brown and red cement dyes. This mix was then carefully trowelled into the shuttering and tamped down with a piece of timber.

The concrete was left for two days and then the shuttering was carefully removed. I find it is better to remove shuttering while the concrete is still in its 'green' (crumbly) state provided I am very careful. I was then able to smooth off the top of the embankment (using the back of an old saw) and then scribe the stonework on the upper surface with a nail.

I also took the opportunity to tidy up some of the stonework courses which weren't as clearly defined. I also and carved indents at the ends of the embankment to take the timbers of the trestle which would be needed to support the track.

A 'timber' trestle at the end of the embankment was made from 5mm foamboard - joints reinforced with triangles of 1.5mm thick plasticard and 2mm diameter half-round nail art gems (from eBay) were applied to simulate bolt heads.

The trestles were then painted dark brown, and dry-brushed with increasingly lighter shades of brown to accentuate the wood grain effect. See How I constructed a set of loading hoppers - pending for more information on using foamboard to simulate wood. The trestle was glued into place using Gorilla Glue which foams to fill any gaps.

Peco 32mm narrow gauge track was then fixed to the embankment and chutes made from off-cuts of plasticard to allow Binnie skips to offload into the back of the hoppers.

Inevitably, there were some gaps which needed filling where the concrete hadn't managed to reach.

A small quantity of the 3:1 mix was used to patch up the fissures and, once it had gone green, the stonework was scribed on. 

Once the concrete had fully set, buff cement dye was painted roughly on to the mortar courses ........

......... and then various shades of cement dye (black, brown, red and buff) were painted on to the stone 'blocks' to give a little variation - stone walls are rarely uniform in colour - at least in this part of Cheshire.

Then (of course) the embankment and sand quarry sidings were tested a few times to ensure they came up to scratch!

On reflection, I probably wouldn't add dye to the concrete mix as the natural colour of the concrete could have been left rather than having to paint the mortar courses to highlight them. I would have preferred to have constructed the rockwork behind the siding after the track had been laid as this would have made building the embankment a lot easier. However, I suppose the meandering nature of the embankment gives the impression that it has been constructed to follow the existing landscape rather than vice versa.

I may have to realign the siding slightly, as it is very close to the first loading hopper. This is a relatively straightforward job - far easier than rebuilding the hopper! I need to figure out where the 32mm line will go at the far end of the embankment. I am favouring building another trestle to take it over the end of the siding before disappearing 'off- stage'. I could extend the border beside the stream and run the siding alongside it which opens up all sorts of other possibilities - but that will have to wait for another day!

Over time, the stonework will weather naturally and I am expecting moss and the ubiquitous Mind Your Own Business ground cover to infiltrate the rock face and fill various nooks and crannies.


Fairywood Light Railway said...

Well this is another superb build Rik. I love the platform its simplicity in construction has made a brilliant looking platform with it's trestle work. How cool does your stonework look. Thats another great build. Can say more about this, but I would need to start a Blog myself, but wouldn't know were to

GE Rik said...

Thanks Rod
I'm quite pleased with the way the embankment had turned out. Also I'm glad I decided to use concrete. I trimmed the hedges at the weekend and ended up accidentally treading on the embankment. I don't think a wooden or plastic structure would have survived!

Ukjim said...

Rik, it looks just brilliant, I love the combination of the wall stonework merging with the rocks. Plasticard?! Never, surely that's real timber there? Overall it really is a beautiful construction. I learned something new with the glue gun technique, great idea. Thanks, Jim

GE Rik said...

Thanks Jim. I am pleased with how it turned out.