Greetings Brian, many years ago, in the 1980's I think, Keith Miller wrote an interesting article for ME called "Lions Crown" about this very issue. Worth getting a look at it.

Also, all locos go better if superheated.

Regards

Brian B

Take a look here Brian.

Nigel has converted from square casting to round

Perhaps somebody can help here because I am not clear what is wrong with a casting? Castings have been used in pressure systems for donkeys years. Are you concerned about integrity or not sure whether the cast top is really like the old original Lion locomotive boiler?

Nick, I can't imagine why a round top would even require anybody to pick up a pencil to do any calculations. Any calculation would obviously come out saying it is ok. I'd be suspicious regarding the persons competence if he or she asked me to do a calculation.

Phil H

Edited By MichaelR on 10/01/2022 18:29:22

Nick,

I ask because a modified outer wrapper is likely to be two flanged, round top plates 1/8" thick at both ends of the outer firebox and a 3/32" thick outer wrapper. Stays correctly fitted of course.

I have asked this before and never got a satisfactory answer. Just waffle.

Phil H

br,

Brilliant. I guess that's why nobody could present any calculations – they were thinking of them warm things with cream and ice cream.

If you go to Lion rescue there are photos of the real thing without the brass cover over the firebox. It appears to be a simple round top 'haycock' boiler. I wonder what LBSC was thinking of with his cast GM affair. It would probably need cross stays above the inner firebox, but apart from that I'd follow the original

A branch of the link says that the 'non original brass cap to firebox added' Crewe ~1930, so what is prototypical anyway?

Edited By duncan webster on 11/01/2022 00:12:31

Brian,

But the boiler is subject to a X2 pressure test.

Hundreds of these things have been built and thousands of other boiler designs have been built with cast gunmetal bushes, cast super heater parts and even cast cylinders.

There could be all sorts of reasons why faults could appear without worrying about a ductile metal casting.

Just my opinion. The fears don't appear to be a reasonable justification to redesign the boiler and reject a sound casting unless you feel that the current Lion design is not authentic for some reason.

Phil H

Duncan,

Yes, but that is the point. I agree that you might have a snag and there would be quite a bit of bad language but at least it is safe.

Also, looking at the Lion, you could cut it out and re solder if you were that unlucky. But that is one hell of a piece of bad luck and as I said before, many of the bushes on other designs are cast GM. How many have them have really failed during the pressure test?

Phil H

br,

Probably not but after the pressure test it isn't realistically going to happen is it?

However, we could do a survey and ask how many cast GM dome bushes etc have actually failed. I bet it is very close to a big fat zero. And they can all be cut out and repaired even if it did happen.

Phil H

br,

Yes, that is why the testing is as it is i.e., pressure test and steam test. And don't forget, if you were that concerned, the casting could be hydraulically tested before it is soldered onto the boiler.

Phil H