GWR diagram O4 5-plank open with sheet (part 1)
There is quite a lot to say about this next wagon, so I am splitting the write-up into two parts - this post will look at the wagon itself, and the next post will describe the wagon sheet (sheet being the correct railway term for what in everyday language we might call a tarpaulin).
The starting point is the Slaters (ex Coopercraft) kit for a diagram O4 5-plank open. It's a nice kit, with good detail and crisp mouldings. There are some inaccuracies and opportunities for improvement, however, which I will describe as we go along.
I started by assembling the body. Because I never trust the floor to be an exact fit, I attached the sides and ends together in pairs (one side with one end) first, then assembled these around the floor. Any gaps can be taken up with some plastikard reinforcement, as seen in the picture. Since the inside won't be seen, I also added a stretcher across the middle of the body to stop the sides bowing inwards:
I realised after assembly I had made a mistake. The corners are mitred but with a slight ‘notch’ at the extreme corner, so the sides/ends fit with one part overlapping the other. I made the sides overlap the ends, so the length of the side moulding determined the overall length, and the width got very slightly wider. this was a mistake, as the overall dimensions would be more accurate if the corners were overlapped the other way. My wagon is therefore very slightly too wide, and too short, but only by less than a millimetre.
The kit comes with an 'underframe' moulding, which spaces the solebars apart. I didn't use this, partly because it gets in the way of brake gear, etc., and also because I don't quite trust these things to get the solebar spacing correct. As it turns out, the solebar spacing is a more complex than one might think...
The first issue is that the bottom flange of the sole bar in the kit is too wide. I decided the most important thing from a visual appearance point of view was getting the outside edge of the sole bar bottom flange in the right relationship with the bottom corner of the body:
To work out how far apart to place the solebars, the relevant dimensions are:
- Prototype width over body: 7’6” = 52.5mm
- Prototype width over solebars, including flanges: 6’9” = 47.3mm
- Kit thickness of solebars, including the flanges: 4.0mm
Therefore the distance between the solebars on the model needs to be 47.3 - 4 - 4 = 39.3mm. I made spacers this length out of 200 x 80 thou strip, to assemble the solebars at the correct distance.
Before assembling, though, I made some preparations for the brake-gear. I replaced the moulded components with WEP etches, described in more detail below. There are 3 vee-hangers - 1 in the centre of one side, and 2 positioned either side at one end for the DC brake levers. For these to sit in the right relationship to the solebar, the solebar needs to be thinned down - otherwise the vee-hangers are set too far back. In the relevant places, I filed the back of the solebar as thin as I dared without breaking through:
I then assembled the solebars and spacers as a subframe:
Before attaching the solebars to the body, the headstocks needed fitting. These have square ends, not the correct angled ends, and are a little short. Adding some small pieces of plastikard fixes this. It's easiest to make these oversize, glue them on, and then file back:
The left hand side filed back, the right still to do:
I used a template to get the angles consistent:
Then a small piece to make the top flange on the headstock:
Because of the way the solebar and headstock meet, there is a small gap that needs filling on the back of the headstock, again with a small rectangle of plastikard:
The solebar assembly was then attached to the body.
The brakes are the kit's weakest area. The brake shoes sit too far from the wheels - something I find particularly irksome and unnecessary. Worse, the push rods are the wrong way round for DC1 brakes - the cross shaft turns in the opposite direction to that on conventional lever brakes, so the left-hand push rod should be above the cross shaft, not below. There is no detail moulded on the back of the brake shoes and push rods, so the moulding can't just be put on the other way round. As well as the vee-hangers and DC1 brake levers, I decided to replace the brake show/push rod assembly with WEP etched components.
The centre vee-hanger in position, packed up on a piece of plastikard:
And the end vee-hangers and cross-shaft:
The above picture also shows the angled gussets that reinforce the joint between the solebar and the headstock on the prototype. I added these with some 5 thou plastikard.
As it turned out, the WEP etchings also position the brake shoes too far from the wheels, so once the assembly was all soldered up, I used a fine fretsaw to cut the push rods away from the central tumbler, and re-soldered once everything was in position on the wagon. The WEP brake shoes and push rods in position:
This picture also shows a few other things. Firstly, the continuation of the side knees down to the solebar, made in plastikard strip, with little cubes of plastikard for the bolt heads. Then there are the door stop springs. The kit comes with long springs, and long banger plates moulded onto the wagon side. These are appropriate for these wagons in their later condition, but not for my 1908 period, so I scrapped off the banger plates and replaced with square ones, positioned for the short stop springs made from nickel silver strip. Rivet heads are spots of PVA glue applied on the end of a piece of fine wire - a handy dodge. Lastly, the safety loops are made from nickel silver strip.
That's about it for below the solebar. The only part I didn't fit at this stage was the 'swan neck' lever that connects the end cross-shaft with the DC brake levers on, and the centre cross-shaft that operates the brake shoes. It is easier to leave this off while everything is being painted, and only add it right at the end.
Next is the sheet supporter - the rail that attaches to the ends of the wagon and holds the sheet up. Unlike the PECO 4-plank wagon in a previous post, this kit comes with components for the sheet supporter. The moulded end mechanisms are quite nice, though the semicircular guide is not quite as refined as one made in metal. Since it is largely hidden by the sheet in this case, I decided to use it. However, I replaced the rather skinny wire provided in the kit for the bar itself with some 1.6mm straight brass wire - much closer to scale diameter.
The ends of the bar were filed and bent to the flat shape of the prototype:
The hole in the end had a short length of brass wire soldered in to act as a pivot, fitted into a hole drilled in the end of the wagon.
Because all but the ends of the bar is hidden, it is easier to make it in two halves, cut to exact length and soldered together afterwards, than to try and bend both ends to get the exact length needed. This also gives an opportunity to add strength in the middle so it doesn't sag or get bent while fitting the sheet:
Here it is, with the cast G.W.R and number plates on (spares from a PECO 4-plank kit) and ready for the paintshop:
One other thing just visible in this photo is all the hooks to tie the sheet to, 5 each side sticking down from under the curb rail, and 3 each end sticking out from the curb rail. The hooks are made from 0.5mm soft iron wire, bent to shape and inserted into holes drilled in the wagon body and held in place with a tiny dab of runny CA glue. I have also added the buffer guides - the buffer heads and couplings go on last, when everything else is done, as the wagon is easier to work on without them fitted.
The paper arrangement the wagon is sitting on in this picture is the method I use to mask the wheels. I paint the wheels black before assembly, and then make a simple 'box' shape folded up from paper, with slots for the axles to go in. This means I can spray the wagon while keeping the wheels free of paint.
To help ensure the sheet conforms to the right shape, as if curving under its own weight where it is draped between the sheet supporter and the wagon sides, I made a former in plastikard:
Other than the sheet itself, which I will describe in part 2, the only other thing is painting and weathering - a mix of Vallejo acrylics to make the red, and some black and brown washes mainly on the chassis. I didn't bother with the top couple of planks, as they will be covered by the sheet, and there are no transfers needed because of the cast plates, of course:
Part 2 will cover making the sheet, but in the meantime, here is another taste of the finished item:
Nick.
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