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Smokebox – or Can of Worms

MikeOxon

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After my previous entry about the Gooch Standard Goods, I had thought that adding the smoke-box would simply be a case of copying the method I had used to fix the firebox. In the event, things were to prove not so simple!

 

The main parts for the smoke-box comprise front and back plates, a wrapper (with a hole for the chimney) and a ring, described as “boiler ring (back of smokebox)”. A moment’s thought pointed out to me that this ring would have to be threaded around the boiler before attaching anything to the front – one trap for the unwary eliminated :)

 

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Unlike the fire-box, there are also half-etched overlays in the kit, to represent the rivet detail on the front of the smoke-box and on the wrapper, so I wasn’t going to have to raise lots more rivets!

 

There were, however alternative overlays for horizontal or inclined cylinders, while the main wrapper also has dotted lines, to indicate where to cut off small sections, in the case of horizontal cylinders. This sent me off on another piece of research, to decide which version I should use.

 

The RCTS volume covering Broad Gauge engines doesn’t appear to mention inclined cylinders, nor could I determine much from the various photographs I have of these goods engines. The Oakwood Press volume of Mike Sharman’s drawings does, however, clearly show inclined cylinders on the Banking Class ‘Plato’ and, less clearly, on Standard Class ‘Cato’. No doubt I could obtain the relevant information from the Broad Gauge Society but, since I am planning to use the boiler for a Waverley Class 4-4-0, which both drawings and photographs confirm to have had horizontal cylinders, I chose this option.

 

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Waverley class 4-4-0

 

So, following the method I had previously used successfully for the firebox, I formed the smoke-box wrapper around the etching for the smokebox front. This was easier than in the case of the firebox, because the sides of the smokebox are straight, rather than having the complex curvature of the firebox.

 

I remembered to thread the ring over the boiler and then soldered the ‘smokebox back’ to the front of the boiler, exactly as I had done at the firebox end (previous post). To fit the ring, I tinned the joining surfaces of both the ring and the smokebox back-plate and then used my soldering iron as a mini-hotplate, by clamping it lightly in a vice.

 

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By this method, I could hold the back-plate, already fixed to the end of the boiler, against the hot iron, while teasing the boiler ring into position with tweezers. The iron melted the tinned areas and the two parts were joined, with no damage to the rivet detail on the ring. So far, so good.

 

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Sadly, I had not foreseen the next problem! Unlike the firebox, the length of the smokebox was not sufficient to allow me to insert my soldering iron so as to complete the joint of the wrapper to the back-plate :( I tried a longer pointed soldering bit, which could just reach, but I couldn’t see what I was doing and, sadly, ended up melting a blob of solder over those nice rivets on the smokebox ring :( :(

 

Time to pause and re-consider my strategy. I turned to Iain Rice’s book on ‘Etched Loco Construction’ for inspiration and found a few options. I decided that my best bet would be to remove the smokebox front and, instead of starting from the front, I would attach the wrapper to the smokebox back in the first instance.

 

Since I had already formed the shape of the wrapper, this was fairly easy to carry out. Next step was to ‘sweat’ the smokebox front onto the wrapper. Since there is an additional overlay, I did not need to worry too much about getting solder on the face of the smokebox front so, as with the ring, I laid the front on my clamped soldering iron and then applied flux and solder from the inside of the smokebox.

 

I found it quite difficult to hold everything in alignment but, eventually, the front of the smokebox was secure. The fit wasn’t as good as I had hoped but the gaps on part of the curve will hopefully be covered by the etched overlay.

 

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Now that the parts were all fitted together, I used some desolder braid to remove the excess solder that I had carelessly run over the detail of the boiler ring. This worked pretty well :)

 

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From this stage, it should now simply be a case of adding detail overlays and various boiler fittings.

 

I realise that this entry has only covered a very small part of the overall construction but it serves to document some areas that I found difficult. I intend to turn my attention next to the design of a chassis for the Waverley class 4-4-0 “Rob Roy”, onto which I shall mount this boiler.

 

Mike

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Hi Mike,

 

Thank you for this very informative build process and the techniques used to build the loco, certainly an enjoyable read.

 

Grahame

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The construction of early locos is never easy; I think you're doing a fantastic job - well done! Really enjoying this blog.

 

Chris

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Thank you, Chris and Grahame, for your encouraging remarks.  I'm really just following my nose and solving problems as they arise.  It's great that others find it interesting :)

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