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Roger M. has been working on a LSWR 1888 gunpowder van. He shares his progress with us.

Building a 4mm scale LSWR 1888 gunpowder van

Part One

Part Two


Part One

Planning

Having built a few models from Plastikard I wanted to use some 0.8mm birch ply to assess the differences, especially the paint finish. The gunpowder van was chosen because of intrigue and the near certainty that there will never be a commercial RTR model. 


Prototype [ref: LSWR Carriages Vol. 4, G R Weddell, and HMRS drawings as below.]

At first the London and South Western Railway ruled that no explosives were to be carried, but they eventually built special vans. With at least one maker on their patch, along with Plymouth and Portsmouth naval dockyards they had little real choice! The first batch were built in 1888 but how many is uncertain. A second batch of similar vans were built in 1900 and there is a full General Arrangement(GA) drawing but again we don’t know how many vans were built. Drawings are available from the Historical Model Railway Society(HMRS), in collaboration with the National Rail Museum, as their drawing number 0990(1888) and 0973(1900). No photos are known to exist and the 1888 drawing shows the body only.


The lack of a chassis drawing for the 1888 batch means some assumptions are needed to build a model and these can be made from drawings and photos of more common vehicles built around the same time. Differences from the 1900 van include:-
- a single long brake lever and cast iron block instead of a double block and V hanger,
- conventional instead of self contained buffers,
- simpler ironwork on the body and solebars.

The small size of both vans is also notable with the 1888 van side door being only 4’6” high!


Construction

It is quite difficult to build a box accurately, especially with thin ply as it is rarely flat, even using a glass surface plate and engineer’s squares, so don’t look too closely at the photos! 

The sides and ends were drawn so that their base was the same and the planks lined up so all could be scribed with a marking gauge in one go. The sides and 1.6mm thick ply floor were designed to fit between the ends as the PVA glued joints would be covered by the side framing. Two partitions were inserted to avoid the roof and sides sagging and to contain a ballast weight, a small piece of lead flashing; see photo below.


 

Solvent welding plastic to ply can be done but uses a lot of solvent so the ply was sanded with old 360 wet & dry paper and given a thin coat of water-based matt varnish. The  headstocks were marked out on 4 x 1.5mm strip, drilled for the buffers and coupling hook and cut to length. They were welded to the body using the glass and square as a guide. The corner posts could then be cut from 1.5 x 1mm strip, tried and welded in position as they go down the ends of the headstocks. They were left slightly long for welding and filed to the roof slope and flush with the headstock bottom surface when the joints hardened.


The next photo shows the top rails cut from 1mm square strip, fitted and welded between the top corners of the posts. It also shows the doors cut to size, more on those later, and the solebars with axleguard castings glued on.

 


The solebars were tried in 1.6mm plywood but were difficult to straighten so 1.5 x 4mm polystyrene strip was used. Axleguard castings are old ones from Fourmost drilled to accept waisted brass pinpoint bearings, fixed to the solebars with epoxy using a jig made of card to keep everything level and a Masokits etched wheelbase jig to ensure correct spacing. 


This short wheelbase van will not be sprung or compensated, however, wheel and axle alignment is critical to reliable running and is difficult with kits. Typical instructions say, “Glue second solebar in place with wheels and bearings in place and check squareness, free running and alignment”: easy. So with your three pairs of hands you do that and when the glue is set you discover chronic misalignment from the direction you couldn’t see! To avoid this problem the solebars were cut slightly long and solvent welded each to a 10mm wide piece of Plastikard with a reinforcing strip between the castings. This allows the solebars to be set up with bearings and wheels and checked on a spare bit of ply; see photo below. It also allows the depth of bearing holes to be checked as the solebars have to fit between the bottom frames of the body; these castings needed relief for the bearing flange, about 3.2mm(1/8”) diameter, as well as deeper holes for the bearing body, about 1.8mm diameter.



Yes, those “craftsman’s clamps” are clothes pegs. The wooden ones are ideal for carving to shape for specific holding duties, including when soldering. A dial gauge caliper was used to measure the width over solebars. The photo also shows guide lines under the floor for aligning axles and reinforcing strips for the headstocks welded each side of the coupling hook slots.


The body side frames were all 3” thick outside the planks, which were 1.5” thick, but the door frames were only 1.5” proud of their planks. To avoid weakening the sides by cutting holes for them, the doors were cut from 1mm ply but sanded down to about 0.7mm thick; this was easy to gauge as it was just one outer ply. The doors were then checked and glued in position hard up under the top rails and dead central between the corner posts. 

The bottom rails were a bit fiddly. They should be 1.5 x 1mm but with a fillet on top to shed water away from the planks. Plastic strip 2.5 x 1mm was used and filed to about 450 for the fillet with a recess under the door. This left about 0.8mm below the floor level and on the full size van this was bolted through a crib rail(other wagon builders called it a curb rail) to the solebar. This is what determines the  solebar spacing and hence the bearing hole depth. 


The rest of the body framing was cut from strip plastic and fitted, hopefully so you can’t see the joints! For the diagonals this was helped by drawing the panel to size on the cutting board to get the angles about right. 

The photo below shows how the door framing was fitted to leave a small gap all round; any variations are due to the door sagging! It looks a different colour to the body frames because it is only 0.25mm thick. End posts from 1.5mm square strip have also been fitted and their tops tapered. 


About 1888 most LSWR goods vehicles had timber solebars flitched with an iron plate about 3/16” thick. This took the strain of carriage bolts and tie rods without using separate washer plates. To represent the nuts and washers here a new technique (culled from RMweb) has been used. Rather than stick on tiny cubes of plastic as in the past, 0.55mm holes have been drilled and 2mm lengths of 0.5mm plastic rod welded in place. More on nuts below . . .



A problem with models of outside framed vans and wagons is that a lot of iron work was used to strengthen the corners, diagonals and hinges. All the ironwork was fixed with coach-bolts inserted from inside with nuts and washers outside.  I have tried representing this with aluminium foil impressed with a scriber, etched brass strip and plastic strip with the nuts made of tiny cubes of plastic, about 0.25mm square, all solvent welded on separately, but they drive you – nuts ! For the last wagon, of which I hope to make a few more, a master was made to vacuum form the strips so I could cut them out with nuts already formed, so this sanity saver will be used again, although a new master is required because the ironwork is different; ‘t was ever thus. 


Part Two

Building a 4mm scale LSWR 1888 gunpowder van – part 2


Vacuum formed ‘nuts’ 

The photo below shows the set-up: a hot air paint stripper, a vacuum cleaner and some bits. 

 

The tooling base is a block of 25 x 50 softwood with a hole cut for a short piece of plastic drain pipe which happened to be a lose sliding fit over the first stage nozzle on the vacuum cleaner. The pipe was glued into the wood with epoxy and duct tape sealed the pipe to the vacuum nozzle. In use the block is held in the Workmate jaws with the hose underneath as seen below. Be aware of safety issues when heating plastic and don’t let it burn.

 


The top of the block is hollowed out to the area of the ‘tooling’ which consists of:-

- blanking plate for a larger area for future trials,  1.6mm ply,

- perforated plate to support the brass tooling,  1.6mm ply,

- brass tooling plate,  0.25mm(0.010”) half hard brass sheet,

- clamping frame,  1.6mm ply fixed with four screws,

- work piece,  0.25mm(0.010”) polystyrene sheet.


These are in order from the bottom up and shown above from upper right anti-clockwise.


In theory the whole assembly is located and screwed together, the vacuum switched on and the hot air gun started and aimed at the plastic sheet from about 70mm range at a slight angle to the vertical. When the sheet begins to dimple into the holes in the brass tooling the hot air gun is stopped and the vacuum switched off. In practice it is a little more variable and some types of sheet cause more problems with shrinkage. As you can see the frame also takes a roasting and mine had to be replaced for this van before any acceptable sheets were produced. However, once the right distances and sheet type have been found it is easy to produce four sheets with consistent results for all the ironwork on the van. The photo below shows the brass tooling and the plastic sheet with dimples; the other side is what we are after. The rows of holes represent rows of nuts on specific bits of strapping so spacing is important. The fifth row down has only two nuts at one end. This is the end vertical corner strip: the two nuts and bolts are on the headstock and the rest is fixed with countersunk screws. This plate includes some corner plates for future bolster wagons (bottom row) so the ironwork was sketched out about twice scale size to check what could fit the tooling area.

 

The photo also shows my lack of ability to put some 0.5mm holes in a piece of brass in a straight line! Good lighting and a magnifying glass are essential but a pillar drill would help.

Holes as small as 0.3mm diameter will produce ‘nuts’ but all holes have to be smooth with no burrs or the plastic will not separate from the brass without damage, leaving nuts in the holes. To cut out the strapping a steel rule is used as a guide with a sharp scalpel so as to leave as small a burred edge as possible. If a burr is raised it is easier to remove it when the strapping has been solvent welded in place on the wagon.


Detailing the van

All strapping is cut as a single strip and solvent welded in place. The forged corner brackets are made of two pieces butted together, giving the adjoining edges a touch of undercut.

The photo below also shows the two slightly different door hasps, made from various bits of plastic micro-strip, and the hinges from round plastic rod about 0.5mm diameter.


Buffers are No 033 from Lanarkshire Model Supplies; close to the LSWR pattern. The brake has a long Wizard lever and pin rack although two goes were needed at the latter as it’s very fragile. The brake pivot is a short piece of 0.6mm brass wire in a plastic bearing block with two levers and the profiled block as seen below. More brass wire 0.33mm diameter is bent to form the horse hook on the left hand end of each solebar and fitted into 0.35mm holes.

 

The photo above also shows I’ve jumped a step or two. The completed body was painted LSWR goods brown including solebars and headstocks. I use fairly thin paint as it’s easier to brush on and get a smooth coat without losing the detail, even if three coats are needed. 

For this wagon two coats of LSWR brown were used with the final coat lightened with grey and dark earth to simulate a slight fading. Below the underframe is black but with a touch of dark earth to allow for dirt without a separate weathering exercise. 


The roof was cut about 1mm oversize from a formed 0.5mm sheet plastic section bought from the South Western Circle some years back. This was fitted around the two central formers and the ends by first ensuring they all lined up, then trial fitting the roof. 


To make from scratch, shape a wooden former to a little sharper radius than required, sand it smooth and varnish it. When dry, wrap a flat sheet of 0.5mm sheet around it and use rubber bands with coffee stirrers lengthwise to clamp the sheet round the former. Heat a saucepan of water to almost boiling and lower the whole thing in slowly so as to let the air out. Wait about ten seconds then remove it and place under the cold tap. Remove bands and strips and check the result. If the sheet springs flat it needs a bit longer, if you can see all the stirrer grain on your “roof” it needs a little less! The latter will also show the blemishes on your former which may need sanding smoother. Unfortunately the thermal properties of different types of plastic sheet vary, but you may be lucky first time.


When successful, the roof can be fitted to the body. I used plastic cement but it’s terrible stuff; either strings or runs where you don’t want it. Epoxy is a good alternative and gives time for alignment. Either way this is when we remember why we drilled a couple of small holes in the floor to let all those fumes out, didn’t we? Looking at the wagon drawing, the proper roof edges were almost flush with the outside framing with the canvas wrapped over the top and sealed on the sides and ends with timber guttering. On the model I filed the roof down to the size over guttering, then placed a piece of cartridge paper over the top, carefully checked the size to leave about 0.5mm all round and solvent welded it in place. Does it work? You tell me, but wait until it’s painted a mucky grey colour.


Lettering is next and this is where things get a bit conjectural. Reading between the lines the LSWR would have been reluctant to advertise the carrying of explosives so it would have lettered this as an ordinary van. However, as with later gunpowder vans a cast iron Notice plate would be fixed next to the door locks. This was drawn in Word Draw in a text box with two borders, one rectangular and one with rounded corners to simulate the fixing bolts, and a scarlet background colour. In hindsight the border should have been thicker but the print shows up even when reduced to about 4mm x 2.5mm!


Given that the drawing has Mr. Panter’s signature I used his large lettering style but the small panels cause a problem. The letters need to be a bit smaller than HMRS sheets so I used POW sides’ press-on type which also have the only known number. These work better on a gloss surface but the railway colours are dull and would secrete micro-bubbles under the transfer so the side panels need gloss varnish, slightly diluted. 


Despite cutting the backing sheets to fit between the diagonals, door and corner pillars it is difficult to place the letters accurately and the R is taking a nose dive. They also look far too bright so a coat of dilute satin varnish with some brown added toned them down. Diluting varnish tends to dull the finish. This photo also shows where the gap between brake lever and solebar is too close and has allowed a fillet of paint to form.


The Tare and Load markings have not been added on the excuse that there is no information. 

The photo below shows its small size against the standard 1881 Adams 18’ low roofed van, a David Geen white metal kit, to compare the finish textures. But with the roof painted, body varnished, warning Notice plate fixed and three link couplings fitted it is ready for service. I usually trial fit couplings before painting but fix them afterwards with epoxy as the links get in the way of paint brushes.


Lessons to be learned from this wagon include:-


- focus on accurate marking out and cutting of basic components,

- the vacuum forming technique works well for producing nuts on ironwork,

- check the axleguard casting hole height as this van is riding about 0.5mm high,

- use a matt varnish after transfers instead of satin to avoid highlights,

- try different plank scribing techniques for cleaner “joints” in plywood,

- the plywood ‘timber texture’ is certainly different, but is it too coarse?

- check an approximate tare weight and load and whether a builder’s plate was likely,

- compare the running of the wagon against those with compensation and springs.


Roger Middleton 25 November 2018

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