A Special Builder's Notes


The Special Builder's Breakfast Club

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18 August 2020


When the Hillman's radiator was first built, it came to me without provision for a pressure cap to be fitted. The earlier Morris Six engine's cooling system was an impeller aided thermo-syphon affair running at atmospheric pressure. Cleverclogs had done a bit of reading and gathered that the general consensus was that cooling systems were more efficient at something above 1 atm. So, sans pressure cap, what were the options? Further research turned up a neat solution in that I could fit a pressure adjuster to the overflow pipe which would act in much the same way.

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Whenever I even slightly overfilled the radiator (there was always a small loss of coolant from somewhere as evidenced by white streaks of anti-freeze on the block) as soon as I come to a halt, there followed a great hissing and flow of steam and water from the overflow pipe. I'd often thought about fitting an expansion tank to avoid this irritating incontinence and the other day, when I was rooting around for something in one of The Great Collector's sheds, I came across an old stationary engine fuel tank.

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It was a bit too long and very rusty, so I chopped out one end, de-rusted the inside, applied a good thick coat of red lead and TIG brazed the end cap back on. That was tricky as the metal was very thin. I blew a couple of holes in the joint but was able to fill them without making things worse. I even had the presence of mind to solder the fittings into the end cap before I joined the two parts - things were going well!

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A good coat of Kurust and a thin layer of Milliput over the brazing completed the operations. The reason for all this work was that it was entirely possible that the leakage past the lip seals on the shaft of the water pump (a recurring problem) was caused by the system being pressurised, even though very slightly. I'll next remove the water pump and renew the seal; remove the pressure fitting from the overflow pipe, connect the new expansion tank and see what happens.

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This is more or less the final iteration of the buck. There's some work to do once it's put together. Horizontal pieces will need to be added in the front wings and I might for the sake of economy, reduce the number of formers in the cabin area.

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The experimental external oil pipe to feed the camshaft shells is under way but I'm short of a 7/16" x 18 tpi tap for the connection fittings. While I wait for the post, I'll turn the block over and decide where best to plug the vertical oilway. It may be possible to block it off at the top - the better option - but that depends on the thickness of the casting in the water jacket below the new drilling.

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A chum had a Motability scooter's lithium ion battery explode in his garage, the consequences of which give pause for some thought.

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