Copper boiler plate flanging, or not?

I suggest Bob starts another thread asking 'What's the best way for a beginner to build a working steam locomotive or traction engine?"

Not something I've every wanted to do, but it's a minefield, perhaps requiring the beginner to become moderately expert before attempting it.

UK hurdles include:

• Boilers operated in public have to be certificated, which depends on persuading an inspector that the design, materials and construction are all safe. Inspectors aren't unreasonable but they are no doubt suspicious of chaps turning up out of the blue, especially anyone full of naive & contentious ideas. Paying to have a boiler certificated professionally is expensive, so most commit to a club. Unfortunately the system doesn't support lone builders who can't join a club.
• Many published designs are amateur, potentially out-of-date, available in conflicting versions, or with mistakes the maker is expected to cope with. They can't be taken for granted: thought required.
• Kits often provide materials rather than self-assembly components easily assembled into a finished product. Copper has to be cut, bent, and jointed. Castings have to be machined, and then all the parts has to be adjusted and adapted as necessary to become a working installation. Fitting is skilled work.
• Materials are expensive, time is expensive, tools are expensive, and skill gaps take effort to fill.
• Not all suppliers are reliable.
• Although the skills aren't rocket-science, neither are they trivial. Silver soldering a heavy copper boiler isn't easy - proper application of heat requiring a suitable torch, hearth and judgment. Hard to tell without trying if one is a natural, or if lots of practice will be needed.

Seems to me making a loco or traction engine is a major investment and there aren't any short-cuts apart from buying a manufactured or second-hand engine. To build one I'd have to address multiple shortcomings in myself and my workshop. I'd start with a well-documented small engine specifically chosen as an easy beginner project, and be prepared to write it off as a training exercise. I don't trust published plans and always redraw them as necessary to spot mistakes and make sure I've understood them. Recognising I'm a long way off being able to solder a boiler successfully, I'd consider buying one. But I don't think throwing money at the problem is the answer, mostly it's down to me. To sort myself out, I'd join a club and establish relationships with the inspector and anyone else prepared to help. Timescale: years!

Which loco or traction engine would the forum recommend as a good starter project for a beginner? Simple design, trustworthy plans, good support, kits that match the plans, and no exotic materials etc.

As Model Engineering is a major challenge compared with gluing Airfix planes together or putting up self-assembly furniture I'm not too worried by suppliers providing parts and guidance rather than sure-fire guarantees. Quite a few on the forum work from raw materials, do their own design, and make their own tools and castings etc. It's what I aspire to.

Dave

Good grief, that sounds too hard for me; I'd better not try building anything.

Andrew

Jason has subtly changed tack. I absolutely agree with the need for water gauge to have its own connection, but in his earlier post he stated that butt strap joints are not preferred in the current UK code without giving us a reference to such a code. Now he refers to fittings for water gauges and gives a reference to what I assume is The Boiler Test Code 2018 volume 1.

This actually refers to butt strap joints at clause 7.1.e where it says that 'Butt straps in copper boilers shall be examined to indicate full penetration of silver solder has been achieved before other jointing is progressed' No one can disagree with that, but it implicitly accepts the use of butt straps. A continuous plate might be stronger than a butt strap, but would be a case of the best being the enemy of the good, if it is strong enough with a butt strap it is strong enough full stop, no point making it stronger

Duncan,

I think Jason answered it earlier. He said that the external butt strap would interfere with the design of that particular traction engine.

Phil H

Edited By Phil H1 on 22/08/2020 15:22:33

I was at the Midland show a few years ago and was told a tale by boiler inspector from one of the Southern clubs.

They failed a bare boiler for bad joints though it held pressure. A decision was made to test to destruction so a foxhole was dug, everything was closed off on the boiler, water added, the fire was lit and a healthy distance was put between it and watchers.

It failed by going Phutt.

Edited By Dave Halford on 22/08/2020 15:34:26

The way to start is to make boilers of less than 3 bar.litres, get used to the skills, seek competent instruction, test a few joints destructively and get to know how to use your desired materials properly.

The rest should be less worrying.

Duncan when talking about butt straps I have only said it is not preferred by many boiler inspectors and a full wrapper in now what tends to be used particularly as it is brazed, this is born out by what reeves have said and supplied. 7.1 Actually says butt straps on barrel joints not wrappers.When mentioning that there are parts of the code it does not meet that has been separate from the joint issue and confirmed today as the gauge feed. No change of tack, just two separate issues you have treated as one.

Bob I really worry about you building this boiler, the other day I pointed out the way the throatplate on the Minnie is constructed and you had miss read that. I have the book and the drawings you mention and they are NOT the same there are some subtle differences not least the 13swg you have already said the design drawing show yet the book shows 10swg on one page and 13swg on another

I suggest you also read the first few paragraph of the Copper Boiler chapter where Haining lists the changes from his 1962 design and what he now (1982) suggests doing

Another thing that you may fall foul of if you merrily carry on without talking to an inspector is that the Drawings and book have failed to show the blowdown valve boss and there is also no provision for washdown holes. The Magazine article does show a blowdown.

As Said a propane torch can melt copper, I know of two builders of the 2" Fowler A7 who managed to burn/melt the fire tubes effectively scrapping the boilers, a problem as the tubes are thinner than the plates so heat up faster and if you go with your thick unflanged plates even more likely to happen.

Please don't "just copy" another design for a much smaller boiler with a lower 50psi working pressure, Do the calculations or if you can't talk to a boiler inspector. If you can't get to a club at the moment then work on some other parts of the engines until you can, they should want to see it during construction anyway not just when complete.

If a commercial boiler is CE marked and the paperwork is good then I believe it should be OK to be steam tested when completed at the quoted pressure.

The 16HP has the same gears flywheel and crank mounts as Superba from Blackgates. The cylinder does not have to be the Church valve version the original it was supposed to be based on was built with a normal slide valve.

Dave Crank and 2nd shaft have different PCD between Superba and 16NHP therefore different gears and the horn brackets 9 Crank mounts ? ) are not the same, I believe the flywheels are the same castings.

However both hornbrackets and gears can be made from scratch without the need for castings as can a lot of the other parts so no need to write off the boiler with the added bonus of making it look more like a 16nhp than haining's "stand off scale" version.

Edited By JasonB on 22/08/2020 18:12:44

Jason,

You perfectionist you.

The real one is a very different beast, however Haining's designs for the 16hp (ME 1st may 81 page 558 gear table) lumps the 16 and Superba together with the same gears. This table also appears in the Superba build.

So a heck of a compromise, but allegedly do-able if you want to.

Even if the commercial boiler is not CE marked as long as you can prove it was built before CE marking became mandatory (2002) rings a bell but as its historic it is no longer listed in the orange code (pretty sure it's in the old blue version though) then it can still be tested no problem. There are still a few pre CE boilers incorporated into models that builders are only just completing!

Paul.

Yes you are right Dave, I had just quickly looked at the hornplate drawing which is the Z7S even though part of the "Superba" drawings. The gear drawings have Superba and 16NHP as same size gears.

However if I ever get round to building the Superba that I have the castings for it will have different gearing more in keeping with full size as will the 120psi BB1 I mentioned being made by someone else.

JB, don't be worried, I look, read and think. I missed that throatplate overlap probably because at that moment I didn't see it as being important which way round it was made, you corrected that, thanks. But I will say that continuing reading the ME and issue 3781 has the Waverly boiler with this joint the other way round, Martin Evans.

I mentioned I had contacted Reeves about the modified BB boiler. Not much of a reply. But the boiler as they supplied needs a joint ring inside the boiler to join the barrel to the wrapper. This ring is flat material 16" long by 3/4" by 3mm. So will go all the way around the boiler. Being 3/4" gives 3/8" on barrel and wrapper. The water gap between firebox front and throatplate is 3/8". So the ring completely blocks this? I have asked what I am supposed to do. Similarly the side stays are provided as copper rivets, what am I supposed to do with them, different to drawing.

Yes, propane can melt copper, but it can't boil/vapourise it like an OA torch can.

SoD makes some important points about old, out of date, builders or designs? I like copper for boilers though, its cost is only part of the cost of the model, but still less than a miniscule holiday.

Thanks to all again.

The joint ring is typically only the full width around the top half of the boiler and cut back to just over half so that it clears the water space but contacts the curved top edge of the throat plate and extends into the lower half of the barrel. Similar to this.

Omit the threaded stays and poke the rivits through from the inside, bend them slightly on the outside so they don't fall out during soldering and cut them off afterwards. I would also suggest not threading the larger stays where the hornplates attach. Out of interest what diameter rivits do they supply?

BUT do confirm these points with your boiler inspector first

As you seem to have a collection of MEs can I suggest reading "My first boiler" by Julia Old starting with 4325, the third part in 4328 EDIT 4329 shows how rivits are used as stays

Edited By JasonB on 25/08/2020 15:50:54

I see Bob you aren't a member of a club.

I'd be very wary of changing from an accepted design without confirming the changes with a boiler inspector first.

Bear in mind that even a change which intuitively makes the boiler stronger (such as using thicker material) will cascade down into changes to many of the boiler dimensions so making parts 'to size' they may not even fit together and then you will have to make more changes which the inspector will need to approve.

Neil

I guess that explains This floating ring / strap in Nigel Bennet's scrap BB1 boiler, it's supposed to be silver soldered to the bridge the barrel to wrapper joint and got forgotten.

That''s the thing, not only forgotten but shows the boiler was not constructed in an ideal sequence, The barrel, throatplate and wrapper should have been one early assembly then it is easy to inspect the joint to check solder has penetrated Looks like a lot more was assembled before soldering, joint may have only been fluxed from the outside so little chance of the externally applied solder going where it should.

That drawing is exactly what I was expecting from Reeves, but no, just telling me to return it in an undamaged condition. Snag is they use thick paper from a shredder and it isn't easy to disinter the parts from this paper. Was missing the firehole ring, found it in the wheely bin.

No other progress either, trying to contact Tyler Steam Models to ask about drawings, buy a new set if necessary, but no response to email or phone call.

That photo of the BB boiler is impressive, built and safe! Would probably pass all the safety tests, simply because the copper and solder do make a good joint.

As to the rivet stays, they are 3/16" diameter, what I wondered was cutting a cross in the end, using a four way chisel to splay the ends out flat and then soldering. Different to threading and nuts, but the volume of copper mechanically holding the stay is the same. End of rivet will need to be annealed prior to splaying. Any thoughts?

The geometry weakens the joint.

In the drawing below Stay 'A' is splayed and soldered, while Stay 'B' passes through the shell and is held by a nut.

When Stay 'A' is stressed, all the force is taken by the solder in tension, marked in red. And the solder could be fatigued due to movements when the boiler heats up and cools down. The arrangement is weaker than Stay 'B' where the same force is transferred by the nut to the outside of the shell in compression (green). Provided the nut and stay are threaded competently, the joint will be as strong as the stay.

I think Stay B also gives more chance of spotting trouble during maintenance because the joint isn't hidden inside the boiler. No experience myself, but I'd guess Stay B would be easier to fit too.

Dave

Dave, I suspect Bob was thinking of splaying the end once it had passed through the two plates somewhat like a bifricated rivit. No nuts are used when rivits are used as stays so your second option is also incorrect too. You are correct that B would be easier to fit as how on earth are you meant to apply solder to A when it's inside the water legs or see if the joint ha sflowed?

Don't see any point in splaying it either way, stick with a tried and trusted method, I'm sure the boiler inspector will say the same

Edited By JasonB on 26/08/2020 19:12:41

Edited By JasonB on 26/08/2020 19:18:15