Allchin Crown Stay

[Peter Howell 1Participant @peterhowell1]

Is there a trick for aligning the crown stays with the boiler outer shell top? I have Farmer’s book but the boiler he is making has a flat top, the Allchin’s is round. They need to conform to the shape as silver solder is not a very good gap filler.

[noel shelleyParticipant @noelshelley55608]

Having looked at the book and drawings very careful fitting seems the only answer. Their main purpose is to stay the crown sheet, this is the joint that matters. The joint to the outer wrapper is less important due to it’s shape. Using a silver solder with a better gap filling property ? CuP alloys, the solder people may have advice. Brazing seems to have fell out of favour now in part because of the fear of zinc loss but since this joint is in the steam space unlikely to be a problem.

If you are a member of a club speak to the boiler inspector or other members in the know.  Good Luck. Noel.

[duncan webster 1Participant @duncanwebster1]

If the joint twixt crown stay and firebox crown is in the steam space it’s time to get on the hand pump!

[duncan webster 1]

On duncan webster 1 Said:

If the joint twixt crown stay and firebox crown is in the steam space it’s time to get on the hand pump!

More like time to drop the fire, but not relevant anyway.

[Nigel Graham 2Participant @nigelgraham2]

Indeed, but Noel does say:

The joint to the outer wrapper…

[duncan webster 1Participant @duncanwebster1]

Ah, teach me to read more closely!

[Peter Howell 1Participant @peterhowell1]

What I was looking for was advice on how to get the curve of the top legs of both crownstays to conform to the curve of the inner surface of the outer wrapper. With hindsight I should probably have been more careful to have done this before soldering them to the inner fire box.

I think I will make a template out of wood that matches this curve then I can more easily bend the crownstays to fit.

[JasonBModerator @jasonb]

Make a concave former and hammer the flange to shape after doing the initial bend, though not so easy now if you have then soldered.

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