Saturday, 8 March 2014

Making a Scratch Built N or OO Gauge British Wartime Pillbox Part 1 Construction

Scratch built pillbox in a copse on an N gauge model railway layout
 
A model railway landscape can be made more convincing if structures are added which help to illustrate the history of a location.  Local and global events can result in changes to the landscape which can endure for many years.

I added a model pillbox to my most recent N gauge model railway layout, detailed in my blog post dated 07 January 2014.  The scratch built pillbox was placed in a commanding position overlooking a railway bridge and surrounding countryside.

A large number of small fortified structures known as pillboxes were built all over the British Isles during the Second World War as part of a defence network in case of invasion.

Pillboxes were built to many designs to suit local requirements using whichever building materials were available in a particular area.  The variety of building materials used meant that pillboxes built to the same design could have a very different appearance.

Pillbox wall and roof thickness varied considerably from approximately 12 inches which were designated bulletproof, to approximately 3 feet 6 inches which were designated shellproof.

Many pillboxes were made using reinforced concrete poured into shuttering.  Timber shuttering was removed when the concrete had set.  Where corrugated iron shuttering was used this was sometimes left in place for added protection.  If bricks were used to create shuttering they were usually left in place after the concrete was poured in.  Rebars were used to reinforce concrete, though sometimes, pieces of scrap metal such as angle iron from bed frames, old railings etc. were also used.

I have chosen to blog construction of a OO gauge model pill box as the components are much easier to photograph than ones required for an N gauge version.  The construction process I use to construct a pillbox for N gauge model railway layouts is the same, though the sizes, thickness of components and surface finishes are different.  I used 1mm thick cardboard taken from a broken box file to create all of the components for the OO gauge model pillbox.
 
 
Scratch built OO gauge model pillbox roof
 
The roof of the pillbox was marked out and cut to shape.

The roof measurements for this particular OO gauge pillbox were:

Measurements marked in red 60mm

Measurements marked in blue 30mm

Measurements marked in green 25mm

Measurements marked in purple 27mm

Measurements marked in black 50mm
 
 
Strip of cardboard marked out for the OO gauge model pillbox walls
 
A strip of cardboard measuring 260mm x 35mm was cut.  A line was marked along the strip 12mm from the top and a second line 19mm from the top.
 
 
OO gauge model pillbox front wall fixed in position with a temporary support
 
A piece of cardboard 27mm long was cut from the long strip to create the front wall of the model pillbox.  PVA was used to fix the front wall to the front edge of the pillbox roof.  Whilst the glue dried the pillbox front wall was taped to a block of wood to ensure that it set at a right angle to the roof.

When the glue had dried the next wall of the model pillbox was fixed to the roof and to the side of the first wall.

I gave each pillbox wall component about half an hour to set before fixing the next.
 
 
All walls fixed to the roof of the OO gauge model wartime pillbox
 
When all sides of the OO gauge model pillbox were glued to the roof I used a thin paint brush to apply PVA along the joints on the outside of the pillbox to strengthen them.  To strengthen the structure further I later applied a coat of PVA all over the interior of the pillbox.
 
 
OO gauge model pillbox ready to mark the position of embrasures
 
I marked the centre of each wall between the two lines which had been marked on the  cardboard strip earlier.  I then marked outwards to create embrasures which were 10mm wide by 7mm high on the front and side walls of the OO gauge model pillbox.
 
 
Embrasures and doorway marked out on the rear or the model pillbox
 
In a similar manner I marked out the doorway and embrasures in the rear wall of the pillbox.  The pillbox doorway measured 10mm wide x 22mm high and the rear embrasures 5mm x 5mm.

An appropriate hobby knife was used to cut the waste cardboard away to create the doorway and embrasures.

Some embrasures on pillboxes I have seen are simple square or rectangular shapes which are the same shape and measurement front to back.

Other pillboxes have stepped embrasures which gave a wider field of vision from inside the structure.
 
 
Stepped embrasure components for the OO gauge model pillbox
 
To create the stepped embrasures I cut some cardboard squares approximately 15mm x 15mm.  I then cut into the square for the middle layer to create a gap which was 3mm smaller in width than the apertures already cut in the front and side walls.  I then did the same with the cardboard for the inner layer, again creating a gap 3mm smaller in width than the one for the middle layer.
 
 
Middle and inner layers of stepped embrasures glued together
 
 
Embrasure components fixed in position inside the OO gauge model pillbox
 
 
OO gauge model wartime pillbox with finished stepped embrasures
 
I glued the pieces of U shaped cardboard together and then fixed them to the inside of the pillbox over the back of the apertures already cut.  The result was a realistic stepped arrangement for each front and side wall embrasure.  The rear embrasures on the pillbox I researched were not stepped.
 
 
Creating a thicker rear wall by adding extra layers of cardboard
 
To create a thicker wall at the rear of the pillbox a second layer of cardboard was added.  I then cut through the rear embrasures and doorway following the edges of the features on the outer layer of cardboard.  I added a third sheet of cardboard to the inside of the rear wall and repeated the process.  The model pillbox looked much better when this work was complete because adding the extra layers of cardboard straightened a slight bow in the rear wall.

Modelling putty was used to fill any gaps or irregularities and allowed to dry overnight.  I then painted PVA all over the model pillbox to seal the bare cardboard.
 
 
Scratch built OO gauge model pillbox with sand added to texture outer surfaces
 
 
Rear view of the OO gauge model railway pillbox with surface texture added
 
When the PVA had dried, I applied another coat and whilst wet, sprinkled fine sand onto it to create texture.
 
 
Example of alternative surface texture using stippled modelling putty
 
For the N gauge model pillbox, I used modelling putty to create a different textured effect.  I added a very thin layer of modelling putty to the walls and roof, then used a stippling action with a stiff bristled brush to create a texture which resembled old, weathered concrete.  I did not add modelling putty to the embrasures as I did not wish to lose definition in such areas.

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