Skip to main content



Work has progressed - the boiler is now complete. The assembly sequence I used was as described in Alex Farmers book on boiler making - and, as it happens, his was also a GWR boiler, although bigger.

As the assembly gets bigger, it always surprises me just how much heat it needs. I work outside, so can only work on wind-free ( and preferably dry) days. Also, I find it essential to use refractory bricks- without them, I'd never get up to temperature.
Even so, it needed two good sized gas torches, and occasional oxy-propane, to complete the assembly. I couldn't do this alone, and gratefully thank George and Russell for their help.

Where ever possible (and that's most of the time), we worked with pre-placed solder - its much easier than applying a stick, as it tends to melt - or at least sag - if you're not quick. We put rings of silver solder under the heads of all the rivet - stays in the firebox. As the solder flowed, each was grasped on the outside with pliers, rotated and pulled into place. This (I hope) helped the solder to penetrate. Also - and very important - old texts always advised reamed holes and minimum fit. Alex Farmer advises precisely drilled and chamfered holes to allow clearance for the solder to flow. Easyflow 2 type solder will fill a gap of a few thou, but not more, and does need a gap for capillary action to work. The pre-placed solder resulted in an excess of solder around the boiler, which is waste, and gives away the amateur status of its maker! - a small price to pay.



I fitted the firebox doorplate and backhead after the stays had been fixed internally. This made it very easy to work on the stays which are pretty inaccessible if you follow the traditional sequence of construction), but I was worried that it might be more difficult to fit these plates at such a late stage. In face, it was perfectly straight foreword - my only slight problem was that the rear foundation ring needed to be nearer to 5/16 than to the 1/4 inch specified in the drawings, so a new piece of copper was machined up to fit.


I made up plugs to blank all the bushes - in some cases, my blanking pieces were in fact the part machined finished components - minus their through -holes.

The boiler was tested - at 160 psi - twice its working pressure - and certified by the club boiler inspectors. Up to this point, I'd left all the stay - rivets t their original length, as, If I'd needed to redo anything major, the extra length is important to get the heat in.

So now they've been cut to length with a Dremmel (and lots of cutting disks) but it doesn't distort the stays the way cutters would.
I plan to re-tset it at 1.5 x pressure, to prove that I havn't compromised the seal on any of the stays.

I've been working on the cladding and false backhead. Older practice was to leave a 3 1/2 in gauge boiler painted but unclad, as far as I can see, with small fittings screwed directly into the boiler. I didn't fancy this one bit, and all my fittings will be attached to the cladding only. Also, I'll put a bit of thermal insulation between the layers - if only to protect the cladding from the stay heads! I remember doing heat transfer calculations a long time ago, and finding that it's the existence of an air gap that is the major factor in preventing heat loss, not its size.
Having tried the boiler between the frames, its now starting to look like a loco. My list of things still to do is only half a page!




Comments

Dianne said…
Norman this is fantastic all your hard work is paying off. It is really staring to look like a locomotive, this is really cool..
I enjoy reading all the work you do. I might not understand it all but certainly can appreciate all the work you do on it..
Have a great week
Tonniece said…
I second that Norman.
I find it all very fasinating, but..alas I too don't understand it all. I guess that's the beauty of learning something new.

Popular posts from this blog

Wheels

What I started with was a set of frames with hornblocks fitted, and wheels turned. So I'm afraid I've no construction details for these. Except for quartering the wheels. You can do this either with a jig,or in the lathe. I've used both methods - a jig works well. Most books and drawings show jigs which are specific to one model, which is not brilliant. Since then, I have seen a general one detailed, which is a far beter idea. I've also quartered wheels in the lathe, which is what I chose to do this time. Two sets of wheels were already assembled and quartered, but, when I checked them, both were different ! The object is to set the two wheels on an axle at 90 Deg to each other -usually, the right leads on British locos. Having said that, the really critical thing about quatering is not the exact angle, but is that all the wheelsets on the loco must be set at EXACTLY the same angle. This is because the wheel relationships are locked by the coupling rods, and any diffe

Coupling Rods

The spacing of the coupling rod centres is critical to the free running of the loco. I measure each side separately and comparing it with the drawing. Any inaccuracies in making up the axle-boxes or in setting the crank-pins will show up here. I started by marking out the centres and outline on the rod blank, then drilled the centres, starting with a small centre drill, then drilling out at (say) 2BA clearance at one end, and 2BA tapping at the other. The rods tapered from 3/8 to 1/4 in. - i.e a taper of 1/16 in. on each side. So I marked out the centre line on the support bar, and another, offset by 1/16 in. I drilled and tapped a fixing for one end of the bar on the centre line, and attached the rod blank. Then I lined up the other centre on the 1/16 in offset line, clamped and drilled through 2BA tapping. Now I removed the rod blank, and opened the 2BA tapping hole on the rod blank to 2BA clearance. Also I tapped 2BA threads in the support bar and bolted the two together. I clampe