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snapback.pngjonte, on 28 November 2012 - 20:58 , said:

 

Thanks again, Penrhos 1920 - that's sound advice.

 

However, now I'm a little more agile after my recent foot op., I've decided to have a bash at fettling up my own boiler from that brass sheet I marked out the other day when I wasn't so agile, using dimensions lifted from the drawings supplied by 'buffalo'. Markings were scratched onto the surface of the brass sheet with the aid of a steel pin and a (rather large, for this job anyway) set square, the lines being highlighted with nothing more than a permanent marker wiped over them.

 

Incidentally, the dimensions were calculated with nothing more intricate than ratios (Direct Proportions) by taking a known measurement from the drawing (in this case 22' 3" or 22.25' in its metric form) and measured using a rule which read 171mm. Subsequently, the scale dimension and that marked out was arrived at by multiplying a given measurement by 22.25, dividing by 171, then multiplying by 4 (for 4mm scale).

 

Cutting the sheet was a doddle using a piercing saw replete with jewellers blade (available for buttons on ebay), the material being cut on the waste side of the marked line - sorry to insult anyone's intelligence here, but I'm using me as the lowest common denominator.

 

Once cut from the sheet, the edges of the boiler were filed smooth and straight, up to the marked line using a file and then drilled (while still flat) using my hobby drill - pin vice will do - at previously marked points for the chimney and safety valve bonnet. Other markings were made for the points where holes will be drilled underneath the boiler for the fitting of boiler bands and also where the firebox will meet the boiler, however, during the annealing process these were lost.

 

At this point, the flat boiler was taken inside and passed through a naked flame on my gas cooker whilst clasped in the jaws of a pair of pliers. The object of the exercise was to observe it change colour to a shade of purple indicating that the metal had become malleable and therefore easily shaped/bent. Although I tried to keep the heat equal by wafting in and out of the flame, there was nothing I could do to stop the edges turning bright orange. Still, as on a previous occasion, there were no adverse effects and once quenched under the cold water tap it behaved more like thin card than metal. Good job too, as with the permanent marker removed and unable to see the tiny predrilled holes without my specs for reference, I went and bent the boiler along the wrong side - Sod's Law!!

Still, once realised, it was easy enough to straighten it out again by pressing underneath an old glass shelf, before returning it to the clothes rail purloined from the airing cupboard, which acted as a suitable former. As geometry is a darned sight more reliable than my capacity to measure to any degree of accuracy, the boiler was a tad short leaving a gap of approximately one millimetre, which was easily filled using a sliver of more brass sheet and bags of 145* solder and Carr's flux. Incidentally, whilst still on its former, the boiler was temporarily held to shape using masking tape so that it could be removed and fabricated. Finally, the soldered closed boiler was returned to the former and filed smooth - well as smooth as I could manage anyway!

Incidentally, if you choose to have a go at this, please remember that the metal remains fairly malleable and will not stand rough handling. For instance, while smoothing the joint with the former resting on my knee, the whole lot moved and the end of the file I was using caught the side creating a dent. However, this was easily removed by rubbing the file gently over the dent and repeatedly sliding the boiler up and down the former. Job done!

 

Surprisingly, the whole thing was remarkably perpendicular when stood on (one) end, the smokebox end. The other end doesn't matter in terms of accuracy or trueness as the bolier has been cut over length so that the firebox (rough) end can be lost inside the firebox itself. One I have the model in my possession, and with further reference to the drawing, I can work out the height above the running plate and cut a bracket for it to rest on- from more brass sheet - which can be soldered on.

 

That's it for now, apart from a quick wash and scrub with some Jif (Cif) and an old toothbrush. I'll pop into Hattons over the next couple of days or so and order a Dukedog and pick up a Dapol City kit to try and work out how next to proceed and try a dry run of parts. In the meantime, I'll try and source a suitable tapered chimney and conical safety valve bonnet. Think I'll give Mr. Finney a call. Failing that, Alan Gibson.

 

Anyway, here are some photos of the tools used and the bit of brass tube produced. Please feel free to ask any questions.

 

Best wishes,

 

Jonte

 

Tools used

attachicon.gif 147.JPG

 

These are wot i made!!

 

 

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Source: Dukedog to Duke: a feasible proposition?

 

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