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Old 01-27-2022, 04:02 PM
JimH JimH is offline
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Default Forming a brass boiler cladding

I'll put this under beginners because this was the first bit of brass we tried to bend. We've had a 1908 Merryweather Gem in the family since the 60s and even by that time, heat and polish had done for the brass boiler cladding. By the mid-90s time had also done for the boiler but that sort of metal forming holds few problems. What always stalled rebuilding this one was fretting about the boiler cladding. No one we spoke to was able to offer much advice and the best we could find was a metal spinner who could turn the top curve but it would mean making it in two pieces and we did not like that idea. If Merryweather did it in one piece over a hundred years ago then we can jolly well do it now.

The old bird on display with its first owners



And the old cladding that's past its prime.



And why things weren't looking good



Were the damage just limited to that sort of cracking then heat treatment, silver solder and effort might have done the trick but the whole thing was falling to pieces.

With very little idea what we were up to other than the knowledge that brass isn't the best material to bash we set out to make a new one. The first thing was to get some polypropylene plates from a heat exchanger and cut discs out of then to be approximately round. These were then bolted together to make a section about 6 inches thick and a little over three feet in diameter.

One thing we aren't short of is lathe capacity so this lump of plastic was mounted in the biggest lathe and the correct radius turned on it.

Machined former



Once done this was mounted on a piece of pipe so we were at the right height.



I have to apologise for our very sporadic (and low quality photography) and there is no record of the sheet of 16swg brass which was rolled and then silver soldered up with a joggled lap joint. The original jointing technique of a dovetailed butt proved properly beyond us. Mercifully the joint is hidden behind the bodywork.

Once rolled, joined and annealed it was possible with the floor crane to slip it over the former. What followed next was not recorded was best described as a disaster - basically we just started hitting it. Fortunately the rolled cylinder was much longer than required so we cut off the mauled bit, lowered the former and started again.

This time we recalled something from David Gardiner's excellent DVD about shrinking using tucks. It was a bit hopeful to do this by hand so we made a punch and die to fit on the end of a body jack cylinder and then spent a while punching tucks all the way round it. This made it look like some spent cartridge from a very big gun.





Once it was annealed it was slipped over the former and we then used dead blow hammers to very gradually draw it in working from the bottom up. What was very interesting is how rapidly the brass work hardens. We got once round with the dead blow hammers and then you could feel it go hard and stop moving under the hammer.

Lift it off the former, turn off the workshop lights then anneal it using the gas/air torch. Then you wait for it to cool - a metal former would have made all this much faster - then back onto the former. We kind of lost count but we think we had it on and off about thirty times.

This is the curve starting to form. After the not exactly glorious early results we were very, very careful not to let any of the tucks capsize so any that looked like they were going the wrong way were gently nudged back over with punches.



Ready to go back on after annealing (yet again). Annoyingly this was too heavy and the former was too tall to lift this on by hand without running the risk of damaging it so it had to be lifted on with a floor crane which slowed things down even more.



We followed the dead blow hammers with flat faced metal hammers to keep the already curved section on the former. This is 16swg so we were having to lean on the hammers pretty firmly to get the metal to move.

Eventually we got to the top and the finish was not pleasing. The black felt tip line is where the chimney sits.



So with very little knowledge but with some wooden mallets (bought a few years previously when we were first thinking about this job) to try to make it look less rubbish. Once it was looking vaguely straight I started on the files.



By which time we were more convinced that it was going to live. The part where the tucks have not been dressed out is where the engine mounts and will be cut away so there was no point spending time on it.

We think that one of the reasons the first attempt went so wrong was the we marked out were the cut outs would be (there are two - one for the engine and one for the relief valve body) and removed that material in the belief that it would make things easier. That appeared to be a mistake because when you were trying to move the metal it seemed impossible to control it. However, it is more likely down to our incompetence. Whichever is the case on this attempt we left it intact.

By the time we'd got down to the wet and dry I was feeling hopeful.



And by the time I'd got some mops and soap on it things were looking very good indeed.



And after only a couple of weekends polishing it was looking nearly done. The grubby section at the bottom is the excess to be trimmed off.



There then needs to be a number of holes cut in it to take the various couplings for boiler fittings but when Merryweather did it originally the holes were cut such that the boiler coupling fitted in precisely so there was no need for shame plates or other ways of hiding the mess you made cutting the hole. How ever we do it this will have to wait until the new boiler is built. Which oddly, is the bit we aren't bothered about in the least.
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Old 01-27-2022, 04:44 PM
crystallographic crystallographic is offline
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Splendid effort, Jim.
Really well knocked out.
Kudos to all on this job!


Have you checked metal thickness at your now-shrunk edge?
Might be seeing a 15+ % gain?
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Last edited by crystallographic; 01-27-2022 at 05:52 PM.
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Old 01-28-2022, 12:28 AM
Mr fixit Mr fixit is online now
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WOW Is all I can say. That is Definitely not a beginner project, and with your explanation it seems you have had a GREAT deal of success.

Super job..! Best of luck on the continued restoration of the engine.

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Old 01-28-2022, 03:39 AM
galooph galooph is offline
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Impressive work, Jim!

Thanks for sharing.
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Old 01-28-2022, 03:41 AM
JimH JimH is offline
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Quote:
Originally Posted by crystallographic View Post
Splendid effort, Jim.
Have you checked metal thickness at your now-shrunk edge?
Might be seeing a 15+ % gain?
Cheers for the comments. We didn't measure the thickness before I started tidying things up. IIRC at the most bent point I think according to calculation there was supposed to be about 23% thicker or something but then a decent chunk of that will have been lost in the filing and polishing.
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Old 01-28-2022, 03:49 AM
JimH JimH is offline
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Quote:
Originally Posted by Mr fixit View Post
Best of luck on the continued restoration of the engine.
The carriage was finished almost a decade ago but ended up sitting round because another project came along and we were fretting about how to make the cladding.



And after we did the cladding that spurred us on to do the engine.



So it is really just the boiler to sort out. Now the current project is almost done the drawings for that have been pulled out again. However, that sort of metal shaping isn't really what this place is about.
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Old 01-28-2022, 04:19 AM
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Gojeep Gojeep is offline
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Wow, what a great result.
Love seeing how you went about it too.
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Old 01-28-2022, 06:07 AM
Jaroslav Jaroslav is online now
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Jim, this is a dream work and a perfect result.
The joy of doing these old things.
In the field of steam, I created the Stirling model for a friend's 50th birthday ...

Jim, this is a dream work and a perfect result.
The joy of doing these old things.
In the field of steam, I created the Stirling model for a friend's 50th birthday ...
I let go of my creativity. The connecting rod is extended behind the bearing and its end describes the ellipse in the lower part. Dedicating only a bottle was too easy....
Snímek 4179.jpg

Snímek 4149.jpg

Snímek 4159.jpg
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Old 01-28-2022, 06:38 AM
JimH JimH is offline
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Lovely. Your work is a little more delicate that what we get up to.
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Old 01-28-2022, 06:47 AM
JimH JimH is offline
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Oooh, I lied. I did take a photograph of the first effort. Or at least the remains of the first effort. Just in case anyone thinks there is any false modesty or sandbagging in my claim that we don't really know what we were up to I offer this...



Oh dear, oh dear, oh dear.

Lessons learned? One or two.
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