Civil Engineering

Making the Grade

One of the great things about garden railways is that you are actually forging a railway line through the land. Your baseboard is your garden and you have to build within the constraints of the land you have. When you come to plan your railway you often find that what looks like a relatively level piece of land is full of all sorts of interesting and previously unnoticed undulations. Another interesting aspect of garden railways is the way they tend to evolve over time, generally starting small and then growing as new ideas come along, experience is gained and finances allow. This has certainly been the case for my line.

My railway started as a dumbbell shape single track mainline and later a branch line was added. The branch line was designed to take nothing more than a loco and two coaches and followed the natural contours of the garden. This included a short, fairly steep slope of somewhere around 1 in 12 but was not a problem due to the light loads. The following year saw a major extension and what was the branch line became main line catering for much heavier trains. Although the slope caused fewer problems than might have been expected I decided that this year’s Spring project would be to create a more even climb and at the same time add a few storage loops in the same place. The questions were – how steep would I have to make the gradient and how do you engineer a constant slope anyway.

The first task was to survey the land. I know nothing about surveying and had no equipment so a little improvisation was required. I did have a spirit level and a laser pointer and I realised that if I blue tacked them together I could create a means of checking levels over a long distance.

I held the spirit level where the slope was going to start, ensuring it was level and pointed the laser at the base of a box located where the slope was going to finish. I then marked the position of the top of the spirit level on a stick which I had put in the ground at the start of the slope. I now knew the distance I had to climb and the length I had for the climb. This worked out at 22 centimetres climb over 6.5 metres – pretty much bang on 1 in 30 which I reckoned was quite acceptable for my railway.

So I knew how steep I wanted the slope to be but I then had to work out how to create this constant slope. At the top and the bottom the current slope was too shallow and in the middle it was too steep.

At first my plan was to create a concrete base for the track but then I realised that other work around the house had left me with some spare 2ft by 2ft paving slabs – just the right width to support four tracks side by side. In approximate terms (and most of my work on the railway is very approximate) these slabs were 60cm long so in order to create a consistent 1 in 30 slope each slab would have to drop by 2 cm. A piece of wood was cut up to create little platform which was 2 cm high and my spirit level was marked 60cm from one end. Now the job became easy. Starting from the top I dug deep enough and wide enough for a paving slab and then checked the slope by resting the spirit level on the ground at one end and the little wooden platform at the 60cm marker on the spirit level. The slab was then dropped in place with a bit of sand underneath and the gradient of the slab checked again with the spirit level and 2cm high piece of wood. The earth removed was shoved further down the bank where it was used for filling.

The photo above shows the loops in place but work on tidying the edge is only half complete.

The storage loops do not run the whole length of the slope and so there are some points and then the lower part is single track. The track base becomes narrower as the points reduce the tracks from four to one. Here I created a traditional cement base shaped to fit and still on the 1 in 30 gradient. For the single track section slabs would have been too wide so here I used a different technique. Firstly I laid the track on the ground where I wanted it to go. I then cut some garden weed protection layer into a strip just a little wider than the track and put this under the track. Once this was complete I filled in under the track with a dry mix of sand and cement packing it in until the track was up to the height I required. This is quite easy and allows plenty of time to think about things and get it right. Once I was happy that all was correct I put a wet mix along both sides of the dry mix and everything stayed in place. This works for me but I know there are many different methods available.

Eventually I got to the lower end of the slope and achieved the required height at pretty much the planned position. The only expenditure was on a few new points so the whole project was remarkably cheap. The storage loops have been laid out and trains are now running on a suitably engineered main line. Maybe not in the same league as Brunel’s main line but fine for my garden. The photo below shows the nice smooth climb on the line in the background.

Chris Morris

Spring 2007.