Welcome to the Yorkshire Group of 16mm N.G. Modellers Ltd: Civil Engineering

Phil Thompson goes in for proper engineering!!

The (very) long term development plans for the Great Willowgarth Railway were set out in the November 2008 issue of ‘16mm Today’.

 

The target for 2009 is to complete Phase 2 of the development, which includes Lovetot station, with its triangular junctions at both ends, together with the triangular junction at Busley station (you’ll need to look at 16mm Today for the plans).

 

The challenge is that all of this has to be built across a steep slope, where the railway track on one side is at ground level and the track at the other is about 90 cms above ground level.

 

Cue some real civil engineering!!  The intention is to lay a number of concrete footings in steps down the slope, with the space between each step being the depth of two or three concrete blocks plus the related mortar layer. A concrete block wall will then be constructed on these footings to achieve the required height.  This wall will be faced with real sandstone to tone in with an existing dry stone wall.  Part of the block wall will have two rows of blocks, with a gap between, to provide sufficient width for Lovetot station.  Once the mortar is sufficiently “off”, the gap between the two block walls will be filled with crusher run and a concrete slab laid on top.

 

The diagram (not to scale)

shows the proposed concrete slabs, which will vary between around 1m and 8m in length, with slabs 2 to 5 (and part of 6) being wide enough for the station, 1, 16 and 7 to 12 being single track width and the rest being double track width.  To complicate matters further, there are gradients to deal with:

 The photos show the work as it is progressing.

 

Firstly, the position of slabs 1 to 6 were marked out “on the ground” by digging down 50mm – 100mm.  String and pegs were used to mark out the straight lines and radius templates (cut from hardboard) were used to mark out the curves.  These templates can be seen in the photos – my set comprises all radii from 4’6” to 7’6”, at 3” intervals.  In use, I rest the template on the ground and draw a metal tent-peg on one side to score the ground, then cut along the marked line with a spade.

 

Each slab is then dug out to subsoil level, to a depth sufficient to provide around 5” of hardcore plus 5” of concrete.  There is an element of “best guess by eye” in this process.

 

Wooden pegs are then hammered into the trench, with their tops set at the surface level of the intended slab.  The pegs are marked with a line 5” from the top, so that hardcore (crusher run) can be rammed in place up to the line.

 

    

Slab 1 is being dug out and the first pegs inserted.  These are rising left to right at 1 in 60.  There is a 2-block step down just before the two arms of the Y join up.

  

 

 

Step 1: the positions of slabs 1 to 6 are marked out on the ground and digging out commences.

 

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The trench is dug down in steps, the pegs ensuring that each step is level.  An extra-long peg is hammered in place in the middle of each step and set so that its top is level with the pegs in the step above.  Another peg is then hammered alongside, so that its top is two or three blocks (plus mortar thickness) lower than the long peg.  The long peg can then be removed and the remaining pegs on that step can be levelled from the first one.

 

My aim was to start with slab 5, then lay two rows of blocks on it, before casting slab 4.  Then lay three more rows of blocks, to reach the level of slab 3 – and so on.  Unfortunately, there was a slight ****-up with the pegs and slabs 5 and 4 were laid 1 cm too high.  To correct this, the mortar between the bottom five courses is a little thinner than it should be.

 

Also, some small alterations have been made as the job has progressed:

 

 

The double-thickness block wall for Lovetot station starts to take shape.

 

 

 

This wall slopes down at 1 in 45.  The trackwork will run underneath Lovetot station, as the branch line to Fosters End.

 

 

Slabs 7 and 8 will be cast here – being short and narrow, they should be the two easiest slabs to prepare.

 

 

The massive slab 6 took a day and a half to dig out.  Over 8m long, it needs to fall at 1 in 56.  Measuring this gradient by eye and guesswork, I managed to dig it an inch or so deeper than necessary.

 

 

The pegs in slab 6 are 67cms apart.  A piece of 12mm ply is placed on the top of the lower peg and then set level with the upper peg, to give the 1 in 56 slope.

 

 

The trench is then filled with crusher run up to the 5” marks and rammed in using the punner.  This was the best part of a day’s work!!

 

 

This is about 1.75 tonnes of ballast, ready to make into concrete for slab 6.  Will it be enough?

     

Progress in July

The spiral is almost complete

 

Slab 6 up to full height

 

Almost there with 14 and 15

 

The spiral goes under Slab 5

       

This will be faced in stone..you won't need to bend down to steam up here!!

photos © Andy Cooper and Phil Thompson

Progress 2010 Open Day..that's a lot of stone!!

   

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