5 inch Lion (Titfield Thunderbolt) Boiler top

I know that many have been made but I'm not at all keen on using a casting for the boiler top.

I have seen pictures of one with a more prototypical rounded top with a circular manhole (am I allowed to call it that?!)

Can anyone point me in the direction of any information?

Brian

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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

Castings were used in commercial model boilers a hundred years ago, and I personally am as suspicious as you regarding the cast boiler top - it is part of the original design and moving away from that might endanger the grandfather rights that enable the boiler to be built and certificated without further calculations.

I which case can I suggest your research ought to include your club boiler inspector.

Take a look here Brian.

Nigel has converted from square casting to round

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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

Many thanks to all for the helpful replies.

br Yes, the cast boiler top is integral and is silver soldered on.

Brian B The article 'Lions Crown' is about making a brass cover for the boiler top. This is decorative only and does not replace the casting.

Nick Clarke 3 I agree about 'grandfathers rights' and this will be something else to ask my clubs boiler inspector.

I have no problems with any required calculations

Essm This is very interesting and will be included in my list of possibilities, which also include making a rounded boiler top with a manhole as mentioned in another of my posts

Brian

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

While I agree that castings have been used for years - unless you stick to an existing design and so take advantage of Grandfather rights calculations are necessary if the boiler I see to comply with the boiler code - otherwise the boiler is uninsurable.

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

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br,

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

Having a 3.5 cast gun metal top, they are a heffty casting about which I would have no fear of failing ! What is more to the point is the specification that whilst the top is silver soldered the joint below it is stated to be brazed ! silver solder gives very little fillet on a joint yet the drawing shows a considerable fillet indicating this IS as stated brazed NOT silver soldered. It is a simple butt joint ! Good luck. Noel.

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

Someone has built a 7 1/4 inch gauge version of Lion and has followed the prototype boiler with a 'Haycock' boiler top and I've seen a 5 inch one with the same arrangement and I think that is what I'd prefer.

My objection to a cast boiler top is that there is no way of knowing if you have a sound casting (I no longer have access to a friendly radiographic department).

Brian

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

Not likely I know, but if the casting is porous, you don't know until you pressure test it, which is a bit late in the day

Edited By duncan webster on 11/01/2022 19:29:16

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

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