Ive finally got the silver soldering sorted. The answer is obvious to all and no doubt features regularly on various posts. FLUX, FLUX and more FLUX.
I had read about it and was concerned about flux life and once it appeared to start deteriorating I had assumed it was done. In fact the deterioration was the state it needed to be in for effective soldering. The tips on the Cupalloy site, pointed to by Firebird, are useful
http://www.cupalloys.co.uk/silver-soldering-tips-c25.html and when I re-read my copy of Martin Evans Model Locomotive Boilers it all became clear.
Anyway all the silver soldering is now complete, although not to the standard I would have liked but I am reluctant to try to fix it further at risk of messing the whole thing up. Ive lost count of the times Ive reworked this. Basically its been numerous cycles of solder. stop, cool, re-pickle, clean, dry, re-flux and try again.
This is the first end plate looking from the inside showing a clear ring of solder that has come through from the other side and with evidence the rivets are soldered in. These rivets only serve to hold the end plates in position during the soldering so are not riveted, in fact it would be impossible to rivet the second plate.
The finished boiler with blanking plugs for ready pressure testing.
During the regular cycles of soldering while the job was in the pickle I had the opportunity to make more fittings
Boring the smoke stack adaptor. The engineers clamp on the top slide allows me to measure the depth with my digital caliper between the clamp and the tool post, rather than miss count the turns on the feed handle. Poor mans DRO.
Finished smoke stack adaptor and top cap
Of course having got this far I had to see what it looked like with the fittings added
You can see the globs of solder that have run down from the fittings. Ill clean those up and theyll disappear under the wooden cladding I plan to cover it with.
Pressure testing.
I expect that this may be a bit controversial but it did the job..
I was going to make the water pump based on the version Firebird did. But have had difficulty getting hold of the small O rings. I also needed a pressure gauge and was going to use the one from this pump as Ive got two of these things.
They go to 300psi and are used for pumping the suspension on mountain bikes. They are fitted with a non return valve, pressure gauge and pressure release button (black button opposite the gauge.
I removed the gauge ready to make an adaptor for it to fit it to the boiler and in trying to work out thread types and sizes realized that the Schrader connector is 5/16 x 32 ME and would fit straight onto the boiler with a simple adaptor.
Ill say it before anybody gets concerned.
Never pressure test a boiler with air, its extremely unsafe. Although trying to do that with this pump would take you a very long time.
I fitted the blanking plugs, filled the boiler with water ensuring no air was trapped, Unscrewed the pump barrel and filled that with water and pushed the plunger in to purge the air. Fitted the pump to the boiler pumped water through the pump and got rid of all the air bubbles and then fitted the boiler filler plug.
I put the pressure up to 50psi, if the pump plunger was getting to the end of its stroke I removed it and, topped up the water and replaced the plunger. In fact I didn't even bother screwing the plunger back into the barrel as there is no pressure against it. With the water in the system it doesnt take more than two strokes to get above 100psi
I had a minor leak from one of the blanking plugs, sorted with more ptfe tape and then did cycles of 50, 70, 90 psi for 15 mins and back to 0. The rated pressure for this boiler, supplied by SandyC with his design, is 90psi. I had reworked Sandys calculations with the materials I had used as was still well within his design margins. So I decide to go for 150psi for ½ hour. It dropped 20 psi over the ½ hour but I have no intent of running this for that long, nor at 90psi so it's good enough for me.
I believe I met the requirements of pressure testing and as long as water is used and not air, and if nobody has any other major issues with it I believe these bike pumps are pretty effective. They are $15US on ebay but no doubt can be purchased from your local bike store.
