GWR 1-plank (part 1)
This wagon is a 'first' in two respects: it is my first wagon with Scaleseven wheels - though it didn't start that way - and it is my first scratch-built wagon in 7mm scale (and for at least 30 years...). The build was also at several points an object lesson in why one shouldn't assume, as we will see.
If it is a scratch-build, where to start? There's not kit to work from, respond to or rebel against. There are not, as far as I know, detailed drawings for these 1-plank wagons, though Atkins et al's GWR Goods Wagons has an outline drawing. The GWR 1-plank wagons came in a bewildering range of lengths and widths. I elected to build one of the 18ft over headstocks, 7'8" over side sheeting types, as this is what the drawing showed, and these seem to have survived in reasonable numbers to and beyond my 1908 period. There are a couple of pictures, in Atkins and in Russell's GWR Wagons Appendix, showing a number of detail differences between the two examples. I decided to mix and match a little, for variety and interest, rather than follow a specific example precisely.
When building these wooden wagons, and in the absence of detailed drawings, it really helps to understand how the prototype was made, and follow that. The spacing between the solebars is determined by the distance between the axle journal centres, since the bearing springs are centred on the journals, and the solebars on the springs, so the weight of the wagon and its load is transmitted vertically down to the journals.
The side, or curb, rails run down each side of the wagon, attached to the solebars but sticking up above them by the thickness of the floor planks. The side planks then sit on top of the curb rails. The dimensions of the curb rails determine the width of the floor, and this is where I made my first mistake. I knew the overall width, across the side planks and curb rail, from the drawing. The end of the curb rail is visible at the end of the wagon (notched to accommodate the headstock), so I could estimate its width. That would then determine the distance across the solebars.
What I didn't realise until I looked at a drawing of another wooden-framed wagon is that there is a packing piece between the solebar and the curb rail, increasing the overhang of the curb rail and wagon body relative to the solebars. As a result of this misunderstanding, on my model the solebars are too far apart, and the overhang is too little. It isn't much, and not too obvious, as the packing piece is fairly thin, but it is an error.
Based on this incorrect assumption, I cut the floor from 80 thou plasticard, with planks scribed on and the top surface roughened with coarse sandpaper to give some texture, which helps when painting the dirty-bare-wood interior later.
Next were the curb rails, made from Evergreen strip - having a good stock of various sizes really mades these kinds of build much easier, as the strip comes cut accurately to size and square.
The curb rails have a distinctive chamfer along the bottom edge, except where the bolts are that hold everything together. I marked it all out in pencil and used the edge of a scalpel blade to scrape the chamfer:
The bolts were made with plastic rod, cut overlength and then trimmed to protrude the same amount using a piece of scrap brass etch with a hole drilled in:
I glued the curb rails to the floor, and while that assembly was drying, I made the headstocks:
The curb rails need to be notched to take the headstocks:
Oh, yes - they are the second set of headstocks, as I made the first pair from the wrong thickness material. Don't assume that the strip of plastic sitting on the bench is the piece you previously got out of the packet to make the headstocks. It might be an imposter...
One thing to keep an eye on once assembly starts is that on the prototype, the top edges of components was often given a chamfer, to help rainwater to run off and not be drawn into the cracks. This applies to the top edges of the headstocks, the side curb rails and the end rails (represented on the model by the end edge of the floor piece). This is easy to do with the edge of the scalpel, as long as you do it before assembly. Reference to photos guided where and how much to do.
A feature of GWR wagons of this period (1870s or so) is that the running number and 'GWR' were incised into the solebar, and I wanted to replicate this. For more discussion of techniques and the prototype context, see:
My first attempt was with the point of a pair of dividers:
A bit of a mess, but not too bad when painted:
For my second test, I used a sewing pin sharpened to a small chisel shape on an oilstone:
I did also order a set of punches, which with a bit of practice gave quite a good result:
However, I decided the shapes of the letters were too far from those of the prototype, and I stuck with my miniature chisel. I first drew out the letter forms, looking at photos, and then started cutting the straight lines with the chisel and a ruler. The curves were done last, freehand. The choice of running number, 4171, with all straight lines, was not an accident...
Next were the ends, starting with the stanchions. These were made of strip, chamfered as before, and the washer plate and nuts added from more strip of the relevant size:
The end plank was made from more strip, and the stanchions attached:
I made the corner plates from a strip of 10 thou, so I could glue on all the nuts before attaching them to the ends and sides, which I find easier. Here are the ends with the corner plates attached, and the strip - marked out in pencil - in the background. Can you spot the next error?
Yup - the end at the top of the picture has the corner plates the wrong way round. I removed the unwanted nuts and added new ones. Don't assume you made the corner plates on the strip in the orientation they go on the wagon. Mutter, mutter, scrape, scape, glue, glue.
Because the sides sit in between the ends, and the ends are located by the stanchions, I didn't want to make the sides until the ends were glued in place. Before I did that, I wanted to sort out how the wheels and axleguards would be attached.
I aim to provide compensation on wagons were this is straightforward to do, and I wanted to try making my own system. I had some axleguards from a WEP etch, so I made these unto units with a piece of double-sided PCB cut to the right size:
For the rocking end, I made a pivot from brass rod and tube - the short pieces of tube at either end are soldered to the rod, while the central piece is free to rotate. This middle part is soldered to the rocking unit, while the ends are mounted to the wagon underframe.
Packing pieces of plasticard adjusted the ride height of the wagon:
It all looks good, right? Well, no - this is where the next assumption would bite me on the derrière. But not quite yet.
I attached the ends, and then cut the sides from more Evergreen strip, and attached them. Elaborate clamping kept things in place while the glue dried:
The corner plates were added in the same way as before, making sure they met the plates on the end with a little bit of melted plastic oozing out to fill any slight gap. Once set, I filed and scrapped this to give the slightly rounded edge of the prototype.
The next job was the axle boxes. In the absence of commercial parts for the GWR grease boxes, I decided to make my own. After working out the dimensions from photos and a few drawings that either give dimensions or are detailed enough to scale from, I built the boxes up from plastic strip. The starting point was the back half of the box, that the spring bears on, with a hole for the brass bearing:
I built the rest of the box before cutting this part to length, as it makes things much easier to have a 'handle' to grip as the parts are assembled.
More layers, made slightly over-wide to be filed down later, made up the front of the box. Again, the strips were over-length, to be filed to the profile of the top slope of the box once assembled:
I added the top detail in 5 thou plasticard:
Final trimming and filing, and we are done:
Except we have to make three more...
One of the pictures of 1-plank wagons I had showed it with 10-leaf springs, not the more familiar 4-leaf, so I decided to model that. I found some springs of the right size and shape - though only 8-leaf - on some ABS LNWR whitemetal axleguards, so I chopped and filed until I had just the springs left. By the time I had done that, they seemed a bit thin, so I stuck them to a piece of plasticard, cut round them and trimmed to the profile of the whitemetal part:
Once I had the springs and axle boxes, I naturally tried these in position on the axleguards. Equally naturally, they didn't fit - the space between the axlebox and solebar wasn't right, and too much of the axleguard etch showed below the box. After some head-scratching, re-measuring and staring at drawings and photos, the penny dropped. Remember what I said about assumptions? It turns out that the WEP axleguards have the hole for the bearing positioned for 3'6" wheels, not 3'. Mutter, mutter...
I unsoldered the bearings, filed out the holes to a slot, and resoldered the bearings in their correct position:
Of course, this meant the packing I had added to get the correct ride height of the wagon was now wrong. I removed it, and filed the top of the axleguard etch to be flush with the PCB (it had projected up above it slightly before). With a small piece of packing for the rocking end, that got the ride height to where it should be.
I added a couple of strips to locate the non-rocking end, and used simple jigs to get the axles the right distance apart (thanks to Mike @airnimal for that tip):
With some additional plasticard pieces to locate the ends of the rocking beam, I had a wagon that could sit correctly on its wheels. I didn't fix the axle units in place at this stage, as it is much easier to do all the solebar and body detailing without getting in the way, and possibly getting damaged.
This seems like a good point to end part 1 of this build - detailing, brake gear, buffers and finishing in part 2!
Nick.
Edited by magmouse
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