Nick Baines

 

 

The boiler isn't round! I've dealt with tapered and sheared boilers before, but not an egg-shaped one. However, the construction method is the same. Two profile pieces were cut and separated by three longitudinals. These were initially screwed in place, the whole thing was soldered up, and then the screws were removed, to form the skeleton shown in the left hand photograph below.

Two of the longitudinals are circular, but the third, located at the bottom of the boiler, is square section and is cross-drilled and tapped in two places. The boiler is located on the frames by means of screws that pass upwards through the frame spacers and into the tapped holes. The wrapper is 0.3 mm nickel silver, which was initially rolled into a circular shape using my rolling bars. This was slid over the skeleton, and with a little bit of persuasion, was made to take up the final shape of the boiler. It was then soldered to the two profile pieces, and along the seam located at the bottom of the boiler where it can not be seen. As usual, I made the wrapper slightly over length and trimmed it back to the correct size after soldering. The smokebox, by the way, is an identical section to the boiler and so the "boiler" component is actually the boiler and smokebox combined.

 

     

 

The firebox is something else again. When I first looked at the drawings, I could see that the firebox was set higher than the boiler, but I assumed that in plan it simply followed the line of the boiler backwards between the driving wheels. It was only after further study that I realised that, moving backwards from the boiler, the firebox actually swells in height and width. The height stays constant, but the width dimension almost immediately diminishes again in order to pass between the driving wheels. The designer presumably thought the small increase in firebox volume that this achieved was worth having, but the end result is a complex three-dimensional shape that certainly could not be represented by something as simple as a skeleton and wrapper.

I decided that the best way to make it was to machine the whole thing from solid. Any sort of built-up construction would inevitably lead to joins that would be hard to disguise. So I clamped a large piece of brass bar to the vertical slide of the Myford, put a milling cutter in the mandrel, and set to work. A vertical slide mounted on a cross slide is not the most rigid set up and restricted me to fairly light cuts, so it was not an instant job. Eventually, however, it was done, inside and out, as the photographs show.

 

      

 

It had to be hollowed out because that is where the motor goes, sticking up vertically into the firebox. Later I filled up the space that was not taken up by the motor with lead, to add weight over the driving wheels. The firebox is attached to the boiler by means of a screw through the central hole seen in the photographs above, so that the bolier and firebox can be removed as a unit to allow access to the motor.

All manner of fittings are to be attached to the boiler and firebox in due course, but the immediate need was for the splashers over the carrying wheels. The back-to-back dimension of 0 Fine scale wheels in underscale, and that meant that the boiler had to be cut away behind the splashers to allow clearance (stop sniggering, Scaleseven modellers!). The boiler and firebox were assembled on the frames, the necessary cutaways were marked out, drilled, filed, and generally massaged into shape. I do not claim any engineering sophistication for the process. I think if I were doing it again, I would fill the bottom of the boiler with Araldite to support the skin, and then flycut the openings for the wheels. Part of one opening impinged on the firebox, which had to be flycut anyway.

The splashers are simple fabrications, and were soldered in place to hide the holes in the boiler. That was followed by a track test to make sure no shorts occurred between the wheels and the splashers.

 

 

 

 

 

 

These are the last two major assemblies. Components for both were cut from sheet and soldered up. The important thing was to ensure everything was accurate and square, because there is not much room around and between the driving wheels. The footplate is stepped over the driving axle, and on the model, I had to make the step slightly larger than scale to clear the gearwheel. Brian Clapperton used the smallest pinion he could, but it still required more than scale space. I pity the poor fireman who had to lift every shovel of coal up and over the step.

The ashpan hides the rest of the gearbox. Both assemblies are screwed to frame spacers.