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Post by springcrocus on Nov 25, 2019 23:35:52 GMT
The blowdown valve gubbins on the driver's side is not needed and is used instead as the blower valve. The drawing shows a rather box-like construction with only a passing resemblance to the prototype. I have tried to construct something a little more realistic-looking while still making it a functional device. A bronze offcut was used to make the body rather than brass as this will carry live steam. After milling up a basic block it was loaded to the independant 4-jaw chuck for machining of the steam entry point which is offset in both planes. A 3/32" diameter hole was drilled straight through and the front turned to create a stem with a 1/4" x 40 tpi male thread.  Over on the mill, the three mounting holes were drilled 3/32" dia for 8BA clearance, then tipped on edge and the holes for the valve and the steam outlet drilled, also 3/32" diameter.  These holes were then opened up to 7/32" diameter and tapped 1/4" x 40 tpi. A 3/16" end mill was run between the holes and round the outer edges to create the raised bosses.  The external circular form of the bosses was created with a home-made tool set in the boring head. This is a piece of 12mm dia mild steel drilled and reamed 3/16" to take ground-up broken centre drills. By setting the tool up to the outer size of the boss, it is easy to create the external circle. The inset shows the form tool next to a standard boring tool.  The boring head is positioned over the hole centre, all adjustment being done directly on the boring head. This shows the first one finished.  The workpiece was then laid over onto it's side and the DRO centred on the middle of the three mounting holes. I need to bring the valve to the right thickness leaving a raised centre section and need to determine the amount of material to remove. Feeler gauges were used to find the distance from the boss to the packing piece.  The feeler gauges were then placed on top of the boss, the 1/4" diameter end mill rested on top and the "Z" axis readout set to zero. This is the height of the tool for the final pass.  The end mill was then run round three sides using the hole co-ordinates as the reference positions. Finally, two blind 6BA holes were tapped on the far side of the block for a pair of dummy pipes to be fitted to. All the rest was handwork with needle files. Once it is painted it should bear a passing resemblance to the full-size valve, even though one of the outlets is missing. It certainly looks better than what was on the drawing.  The innards and other connections will be covered later. Steve |
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Post by Cro on Nov 26, 2019 9:12:37 GMT
I started reading this and got very confused early on, blow down valve, blower? Looking at photos and still no clue, get to the end.....oh! He means Duplex Valve!
This was the large and small ejector steam valve with the blower steam feed as the take off at the top.
Just in case you were wondering :-)
Adam
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Post by springcrocus on Nov 26, 2019 11:10:22 GMT
I started reading this and got very confused early on, blow down valve, blower? Looking at photos and still no clue, get to the end.....oh! He means Duplex Valve! This was the large and small ejector steam valve with the blower steam feed as the take off at the top. Just in case you were wondering :-) Adam Thanks for that, Adam, I haven't a clue what half of these things are called. The drawing tends to muddy the waters at times.  Regards, Steve |
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Post by springcrocus on Dec 2, 2019 10:29:37 GMT
I haven't taken many photos this time, they would just be repeats of previous ones. As mentioned last week, after filling the boiler with water I had a pronounced drip from the foundation ring although cascade might be a better description.  The problem was a poor fit at the end of the infill segment where it tapers away to nothing.  Easily remedied, however, now that the segment is securely soldered in. After filing the area flat, I drilled a 2.3mm hole, tapped it 8BA and fitted a 3/8" long phosphor bronze screw. Two stays on the backhead needed addition solder and one on the side, all inside the firebox. And, of course, the blowdown bush.  This time, we decided to do all the jobs at the same time and this meant we needed to be able to move the boiler whilst hot. The first setup was with the boiler standing on the firehole and with it's nose in the air. I also cut a piece of thermal block to fit nicely into the combustion chamber so that the heat didn't all vanish up the fire tubes.  Using the cyclone burner in the box and the big nozzle outside, we warmed the firebox until the flux started to melt, then we changed to oxy-propane and brought the local area around the two stays on the backhead up to temperature. A 1mm rod was used to solder both stays. The blowdown bush was done next with propane only, then the box was laid on it's side and the dodgy stay there done the same way. Finally, the box was repositioned with the foundation ring uppermost and the the main burners brought back into play. The screw had been slightly loosened to allow solder to penetrate and additional solder was also added in an area we thought might need a bit more. At this point I need to offer thanks to John the pump. A couple of weeks back I knew there would be a problem with the two lower backhead stays and John kindly offered me the use of his oxy-propane kit and the oxygen bottle. At odd moments I've been practising with scraps of copper getting the hang of controlling the flame and the ratio of gases. It's interesting that the hottest part of the flame is not the same as the hottest part of an oxy-acetylene flame, and I found that if I used too much oxygen, it oxidised the surface of the metal and seemed to kill the flux. That practice was invaluable and I'm far more confident using it now. Back to the boiler, it went into the pickle while we had lunch then, after a quick rinse, the test rig was hooked up and the boiler filled. No drips or weeps until about 30 psi when a faint hissing sound was heard. There was a pinhole at one of the tube-to-front tubeplate joins where a minute spray of water was coming out. Never mind, a job for next week. Otherwise, it's looking good with the previous problems satisfactorily resolved. Steve |
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Post by Jim on Dec 2, 2019 20:28:04 GMT
Brilliant work Steve.
Like you I had to get used to the differences between using Oxy Acetylene versus Oxy Propane but now I've worked it out I much prefer the Oxy Propane and it's safer too. The Britannia boilers soak up a lot of heat don't they?
Jim
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 961 
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Post by don9f on Dec 2, 2019 20:51:04 GMT
Well done Steve and your “assistant”....
Cheers Don
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Post by springcrocus on Dec 3, 2019 22:59:11 GMT
....The Britannia boilers soak up a lot of heat don't they?
Jim
Indeed, they do, Jim. Twenty six kilos of copper, trying to reach thermal equilibrium during the heat-up. And all trying to radiate that heat away again. That's why we spend a good amount of time setting up the blocks to keep the heat in. It seems to have worked for us so far. Regards, Steve |
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Post by springcrocus on Dec 6, 2019 17:31:33 GMT
I was able to close the tiny leak at the front tubeplate with a ring of 1mm solder around the offending tube and a gentle heat-up all around the tubeplate until all the flux had melted. I had laid it on all over and, by keeping the flame moving everywhere but directly at the solder ring, I was able to see the solder ring slowly melt down into the joint without any of the other joints going silvery. At the next pressure test, I found a small accumulation of water in the combustion chamber and this was, potentially, a more difficult problem to attend to. My fear was a leak at the flange as this would be extremely difficult to get to. However, it turned out to be a similar leak to the one at the front, this time with one of the superheater tubes and discovered using washing-up liquid.  To try and keep things reasonably safe I screwed a pressure gauge into one of the bushes to monitor the pressure since I was using compressed air instead of water to find the leak and kept it below 40 psi, the level of the last hydraulic test.  The first fix I tried was to swage the tube slightly and turned up a hardwood bung with a one and a half degree taper for the job. This was set in the end of the tube and given a couple of sharp blows with an extension through the firehole. Didn't work, though.  So my colleague and I set up the boiler for another heatup to seal the tube. However, we cheated slightly because he had a few sticks of the old cadmium-bearing solder and this melts fifty or so degrees below the modern stuff. A ring of this was laid around the tube end and heat applied both in the firebox and through the dome bush with cyclone burners.  After what appears to be a successful melt, the boiler is once again in the pickle. Steve |
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JonL
Elder Statesman
WWSME (Wiltshire)
Posts: 2,990
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Post by JonL on Dec 6, 2019 17:33:56 GMT
I read something on another forum that said fresh solder has a lower melting point than the solder you have already applied, is this actually the case? I can't get my head round the physics of it. But apparently it does make repairs a tiny bit easier.
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Post by Deleted on Dec 6, 2019 17:52:40 GMT
I read something on another forum that said fresh solder has a lower melting point than the solder you have already applied, is this actually the case? I can't get my head round the physics of it. But apparently it does make repairs a tiny bit easier. That is true Nobby..with careful placement of heatsinks it is possible to step solder using the same temp silver solder. I can't recall how much more heat it required to remelt silver solder but it is very noticeable if you have new and old under the torch... Keep up the good work Steve... Pete |
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Post by coniston on Dec 6, 2019 20:32:54 GMT
I believe it is due to some of the zinc burning off during the first melting, therefore changing it's composition sufficiently to require a higher temperature to re-melt it. I'm sure the guys at CupAlloy will advise.
Chris
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uuu
Elder Statesman
your message here...
Posts: 2,859
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Post by uuu on Dec 6, 2019 20:44:30 GMT
What you get is diffusion of the solder into the copper, and the copper into the solder, so the joint is made of a new composite of the metals present.
Wilf
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Post by springcrocus on Dec 6, 2019 21:57:14 GMT
During the afternoon, after a quick clean, the boiler was pumped up.    Steve |
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Post by simplyloco on Dec 6, 2019 21:59:32 GMT
During the afternoon, after a quick clean, the boiler was pumped up. Steve A picture speaks a thousand words!  Well done. John |
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Post by coniston on Dec 6, 2019 22:38:14 GMT
What a great result after your hard work and perseverance, Well done.
Chris
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Post by steamer5 on Dec 7, 2019 5:48:13 GMT
Who’s a happy boy then?
And rightly so! Well done!
That deserves a soothing ale......... oh ok make it 2 each!
Cheers Kerrin
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kipford
Statesman
Building a Don Young 5" Gauge Aspinall Class 27
Posts: 575
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Post by kipford on Dec 7, 2019 9:32:51 GMT
Steve
Great work, what a nice xmas present to yourself.
Dave
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Post by Roger on Dec 7, 2019 10:55:10 GMT
Hi Steve,
A superb result, and an example for all of us to learn from. Carefully weighing up the methods to better suit your needs is something that everyone needs to do in my opinion. Adapting when things don't quite go to plan is all part of the game, I doubt if anyone has built a boiler without some hiccup, even if it's not their first one.
Anyway, you've plotted a successful course through this tricky subject and come out very much on top. You can give yourself and your trusty assistant a well earned pat on the back. I'm very impressed.
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Post by David on Dec 7, 2019 11:16:14 GMT
Great result! The whole thing seemed to go very well and so few leaks really speaks for your workmanship. It doesn't look to be an easy boiler to make and you've sailed through.
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Post by delaplume on Dec 7, 2019 11:38:01 GMT
Hi Steve, A superb result, and an example for all of us to learn from. Carefully weighing up the methods to better suit your needs is something that everyone needs to do in my opinion. Adapting when things don't quite go to plan is all part of the game, I doubt if anyone has built a boiler without some hiccup, even if it's not their first one. Anyway, you've plotted a successful course through this tricky subject and come out very much on top. You can give yourself and your trusty assistant a well earned pat on the back. I'm very impressed. Yes-----------------I'd second that.........Nicely done, Steve and just in time for a Happy Christmas..... I'm looking forwards to seeing the final photo of this sequence ie}---- Fully tested and stamped with supporting documentation... |
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