Copper boiler plate flanging, or not?

Oh dear, I got the wrong end of the stick on that one. Sackcloth and ashes again!

Hi Bob,

Every boiler inspector has their own interpretation of the rules, and in general they tend to be pretty conservative preferring established practice over innovation i.e. erring on the side of caution and proven practice.

Any views here count for nothing if your boiler inspector doesn't approve of a change.

Whether a club member or not, I suggest you choose your boiler inspector now and agree any changes with them. They may also be able to offer useful advice.

Neil

Yes, as Jason says, poke rivet through to the outside, cut a cross in the end, heat to red to anneal, hit with suitably shaped punch to flatted down the four quadrants, silver solder.

Many boilers use rivets but just solder them on the outside, thought that splaying them would provide a similar mechanical hold a a nut.

Just an idea. One day might be able to get along to a club, but not at the moment.

The reason for using a long rivet is that the part that sticks out can absorb heat more easily. This will help to get the silversolder to penetrate al the way thru the wrapper. If you do it your way you also risk bending the rivet when you splay the end.

I have built three locomotive boilers (two 3.5” and one 7.25&rdquo and have always used this method whit great success. I recommend that you by a book by Alec Farmer title, Model Locomotive Boilermaking. I met him when I made a trip to UK 1988 and was invited to his workshop and got a signed copy from him. He was very skilled, and I think you should read his book.

Jan

ME 3342 (5-18 April 1968) has an to-be-continued article by PF Janes describing how he and members of Reading SME deliberately destroyed 5 boilers by 3/4 filling them with water, plugging every outlet, and heating with a propane burner in a bunker. A 0-600psi pressure gauge was read with a telescope.

Only one went bang. It was an un-flanged soft-soldered pot boiler of the meths burner type that failed at 110psi when the end-plate blew out. The boiler escaped from the bunker and hit a tree 40 yards away. A silver soldered version of similar design took 600psi, surviving badly distorted. After removing the gauge, the boiler was heated again in an attempt to explode it, but after 15 minutes steam escaped through a pin-hole blamed on left-over flux.

Test three was of a 5" locomotive boiler. The builder (Mr Janes) made the boiler 2.5" longer than designed without increasing flue diameter only to find his improvement caused it to steam poorly. The stays were soft soldered. This boiler lost steam at 165psi due to solder melting at the stays but was otherwise sound - no distortion.

Unfortunately I don't have ME3343 and can't say what happened next!

Dave

Hi Dave,

I have sent you a PM.

Thor

Thanks to Thor, I can complete my summary of PF Janes boiler bursting report.

Test 4 was a representative O gauge boiler with 3 external water circulating tubes. Developed a slight leak at 610psi and was distorted at the end filed and polished for appearance. (The other end was left double-filleted.)

Test 5 was of a rejected 3½" gauge boiler that took several hours to caulk for the test due to poor workmanship. However despite being a reject it took 115psi before leaking steam, and there was no distortion.

1968 Conclusions:

• Boilers caulked with soft-solder are likely to fail by the solder melting rather than a disastrous burst.
• Not necessary to flange end-plates of small pot-boilers provided they are silver soldered.

Plenty of room for more experimentation. Any volunteers!

Dave

Spoke to Reeves, I will try to get some drawings from Haining Steam Models to see what he says.

I have got the Alec Farmer book, but he swears by oxy-acetylene heating, I am not so sure. For soldering the stays OA seems ideal, tight flame and do them one at a time, but still have a 3300 deg C flame.

Don't see that it matters if the rivets bend in the middle, boiler pressure never going to straighten them so they will continue to stay the plates. Besides only 3/8"" or so between the plates so pretty stiff, not much more than the diameter.

Can't find my gas torch, still not got a hearth, progress is slow.

Interesting tests on boilers. Soft solder doesn't seem a good option, but silver solder seems to take almost anything.

Any more? Seems an expensive hobby even at £4 kg scrap value!

All thats required is a tap sideways where the rivet pokes through just to stop it falling out while heating, it's the solder that does all the work.

In bending the shank of the rivit will effectively be shortened and therefore the gap between the two plates reduces. You then move on to the next rivit and that reduces the gap a bit more making the first splayed head loose so not the best idea in the world. It is OK to pein the head of threaded stays as the thread stops the plates from closing up but still requires a light touch to avoid bending the stays when dealing with soft copper boilers and out sort of stay diameters.

Earlier you mentioned the need to anneal the rivit before splaying, that's unlikely to be needed as the supplied rivits are soft enough to form snap or CSK heads on and your splaying is unlikely to need any more effort than that.

While looking for your torch you might want to see if you can find two along with bottles and hoses as it is often easier to have one applying general heat and a second going around around as you apply the solder, a second pair of hands will also help here.

As several of us have said all that is needed is a slight bend so they don't fall out then solder. Backhead and throatplate ones generally have heads on the outside for looks unless a dummy throatplate is being fitted in which case they go with heads inside the box. Side stays are usually done with the heads on the inside as it's easier to file or machine down the protruding ends where they are easier to get at plus they can be trimmed to give less protrusion than a rivit head so don't stop the hornplates from sitting close enough to the firebox sides. Designs where the hornplates fit flush to the boiler must have heads inside and a good chamfer to the hole so a ring of solder is left when the excess is flushed off.

Edited By JasonB on 28/08/2020 20:07:00

There is matter of the added advantage of having the heads inside, the head protects some of the silver solder joint against some of the sulphur attack from the burning coal.

If you silver solder the inside joints first, when you solder the outsides, the cooling effect of the firebox keeps the inner joints from melting when you do the outers. Provided always that you are quick enough and do not overcook them.