REBUILDING A WINSON KIT – MORE DETAILS
As 16-year-old Sussex Miniature Locomotive Society member Sam approaches completion of his rebuild of an unfinished Winson kit, various ‘just jobs’ need doing...
It was now December and school had broken up for the Christmas holidays, so it was time to finalise the assembly of the superstructure. Most of the decorative pieces had now been completed and etched primed. This meant several days could be spent test fitting the items onto the cab, side tanks or the running plates.
These items included the cab and side-tank hand rails, lamp brackets, steps and toolboxes. Of these, the ‘dummy’ toolboxes would require further machining as they would not sit flat on the running plates due to them fouling on the bolt heads and bases of the wheel splashers. However, the toolboxes had already been etch-primed so this was subsequently (and hastily!) removed.
To machine them, the toolboxes were mounted into the vertical slide on the lathe and a further 1⁄16-inch was machined from the 45-degree chamfer on the back (Photo 28), this meant they would now sit flat on the running boards and a fresh, new coat of etch primer could be applied.
Another box to tick on the ‘to-do’ list over the Christmas break was to mount the buffers and buffer stocks. Although previously assembled, the buffers had different fits in the stocks with some protruding more than others as the design for the front buffers was different to the rear.
Taking stock
We decided to take all four buffers and stocks off the locomotive to see if they could be improved. After disassembling them, we also found that all four were each subtly different! As originally designed they had an unconventional separate back plate from the stock, and we decided to start the modifications here as in an ideal world, they would have originally been turned from solid stock or silver soldered together.
We decided that we would fabricate four new back plates and keep the original stocks because they were in reasonably good condition. However the original back plates were inconsistent in depth and two of them were warped! The back plates were 1 ¼ -inch square and by chance, there was some 1 ¼ -inch by ⅛-inch bright mild steel flat available to us – how very convenient!
Four pieces just over 1 ¼ -inch long were cut and then machined to 1¼-inch exactly using the vertical slide on the lathe. Once to size, each square plate was set against the face of a four-jaw self-centring chuck before having a 7⁄16-inch hole drilled through their centres. This hole was then counterbored out to ¾-inch diameter by 1⁄16-inch deep for the buffer stock to locate in for silver soldering.
Once counterbored, the dividing head made another appearance to drill the four mounting holes on the corners of the back plates. For this, the four-jaw self-centring chuck was mounted to the dividing head.
Each hole was spotted on a 17⁄16-inch pitch circle diameter to match the buffer beam. The back plates were positioned against the face of the chuck to ensure that they would stay square. These corner holes were only spot drilled to ready them to be opened up in the pillar drill, the final size of the holes would be
2.2mm to make them big enough to clear an 8BA bolt.
Soldering on
With the holes drilled, the back plates were then ready to be silver soldered to the buffer stocks. Silver soldering steel proved to be a little tricky as the metal would swiftly oxidise, causing the solder to not penetrate into the joints sufficiently. This meant that a couple of the back plates had to be cleaned and heated twice to ensure the two items were soldered properly.
Once clean, the back plates and stocks were put to the side for now so we could focus our attention on the buffer heads and shanks which were retrieved from ‘the parts bin’. These had an interesting design and also matched the stocks – they were all different from one another! The 1½-inch head and ⅝-inch shank were cleaned and prepared for modification.
Two of the four shanks had a ⅛-inch wide by ⅜-inch long slot machined lengthways underneath for an Allen screw to locate into; this was presumably designed to stop the buffer head from falling out and rotating in the buffer stock. The other two shanks only had a central bolt screwed into the back face of the shank and through the buffer beams to prevent the buffers from falling from the stocks.
Hybrid plan
For consistency, it was decided to adopt a hybrid design with Allen screws to prevent the buffer from rotating and falling out of the stock, and a central bolt being used to guide an internal spring. The first task was to mount two of the ⅝-inch shanks into the trusty vice on the vertical slide to machine the ⅛-inch wide by ⅜-inch long slot, this proved to be a challenge but we eventually did it!
Next, all four shanks were drilled ⅜-inch diameter to a depth of ¼-inch to accept the spring with a further 7⁄32-inch hole drilled to a depth of ¼-inch and tapped ¼-inch x 40tpi to accept the central bolt. This
bolt was then silver soldered into place using some ‘Easi-flo 2’ solder.
Once up together, the final task was to drill the bottom of the two stocks 2.3mm and then tap to 6BA to accept the Allen cap bolts (Photo 29). Trial fitting and final assembly ran well, proved that the operation was successful and by luck, all four back plates matched the mounting holes in the buffer beams! The four buffer assemblies were then removed from the locomotive and etch-primed to keep them clean.
By the end of the Christmas holidays, the locomotive was all but fully assembled with just some minor superstructure items left to finish. However, as it was the end of the holidays, it was going to be back to working just on the weekends for me!
Next steps
Below the running plates, the four step fabrications required finishing. The two rear steps are located below the cab doors and the two front steps are below the fronts of the side tanks. Unfortunately, two pairs of steps were missing from the kit when I bought it; these were both the front pairs. As a remedy, I would have to machine some more steps from brass bar.
With each step being the unequal size of 5/16-inch by 3/8-inch, the first job was to machine down four lengths of 3/8-inch square brass to those dimensions, each of which was 15/16-inch long. With these lengths all equal and to the correct size, each step was carefully held in the vice on the vertical slide.
A 5/16-inch slot drill was then used to machine the ‘step’ into the bar. This was a delicate process with very small cuts to get to the required depth and luckily there was only one mistake made over the four steps, so I will count that as a success!
Three 1.7mm holes, to clear a 10BA bolt, were then drilled at 3/8-inch centres in the back of each step to match those in the back plate to which the step bolts onto using some 10BA brass dome-head bolts (Photo 30).
With the steps and buffers finished and mounted, there were just a few more jobs left to be done before declaring the locomotive to be ‘up together’! The first of these were the handrail stanchions – two of these would be attached to the centre boiler band, two would be mounted to the side of the smokebox and one on the front of the smokebox above the door.
The two on the sides of the smokebox were added first as the holes in the smokebox had already been tapped ready for them. I then added the stanchion on the front above the smokebox door, only for the head of this stanchion to become detached. Luckily Andrew my mentor had some spare stanchions to hand, but these were threaded 5BA instead of 6BA as on the kit versions. This problem simply resolved by enlarging the hole on the smokebox front to 5BA to match.
“We decided
to take all four buffers and stocks
off the locomotive to see if they could be improved.
After disassembling them, we also found that all four were each subtly different...”
Bare metal
With three out of the five stanchions in place, the handrail that wraps around the boiler barrel and the smokebox was added. The original 1/8-inch mild steel handrail was also replaced and instead a length of 316 stainless-steel rod of the same diameter was used. This was because painting of the handrail in-situ was considered, but I decided against it because I much preferred the look of the bare metal, therefore, needing a stainless steel rod instead that would not corrode and tarnish.
Bending the 90-degree radii at the corners and then the curve over the smokebox door was quite tricky and time-consuming, but with patience it was achieved.
The final job was to attach the remaining two stanchions which were held by the middle boiler band. Locating these with the band in the correct position was a very delicate task. It was also decided that two brass bushes would thicken the band where the stanchions would screw in. As the band was less than 1/32-inch thick, screwing the stanchions straight into the band itself would certainly be a bad idea! Fortunately, there were fairly large cut-outs in the boiler cladding so the bushes would protrude into these voids and allow the stanchions to be screwed from the outside of the band rather than having a nut attached to the inside.
The tricky task of marking the correct height on the band from the smokebox stanchions took some time and was achieved entirely by eye. One of the advantages of using a bush was that the bands could be drilled
2.3mm and tapped 6BA as if the stanchion were screwed in directly.
We could then check and adjust the holes, if necessary, before opening out for the bush. As it turned out, any adjustment was barely necessary and 0.1mm by 0.1mm, the bands were opened out to 3/16-inch to accept the bushes.
Once they were to size, a length of ¼-inch brass rod was drilled 2.3mm and internally threaded 6BA. A 1/32-inch step was then turned down to 3/16-inch diameter on each and this would locate in the band. A 1/8-inch thick head at the full ¼-inch diameter was left on each bush.
With the two bushes complete, they were silver soldered into the band using some more Easi-flo 2 solder before cleaning and then trial fitting to the locomotive. The test fitting was a success – the handrail mounted into its stanchions quite nicely and looked very smart on the front of the locomotive (Photo 31).
Now take it apart
With the last few items now attached to the locomotive we could stand back and admire our achievement so far before starting the process of disassembly and then final painting. There were still a couple of mechanical jobs left including strengthening the brake mechanism in the cab, linking the draincocks to the cab and sealing a couple of the boiler fittings. These could be looked at once the superstructure had been removed...
■ Parts 1 to 5 of this series appeared in the March to July 2021 issues of EIM – you can download a digital back issue or order printed copies from www.world-of-railways.co.uk/store/ back-issues/engineering-in-miniature or by calling 01778 392484.