Supporting > Boilers

Calbourne - 5" gauge boiler

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springcrocus:
I have started a build log for my Adams "O2" locomotive in another section but wondered if members might be interested in how I constructed the boiler as a separate topic. I'm not a very experienced boiler-maker so it might help someone who is contemplating making their first boiler. I am in the UK and it has to comply to the current UK boiler regulations which differ from the rules elsewhere in the world.

Also, we can no longer purchase cadmium-bearing silver solder so the boiler has been constructed entirely with cadmium-free solder, which is a completely different beast to the old stuff. It flows like water, for a start. I had a colleague assist in the making because I've found that it is much easier with two torches on the go when it comes to silver-soldering large masses of copper.

Amongst the first things I made were some formers for flanging the various end plates. I made these from 20mm MDF as I have used this before and found the material works a treat. The front and back firebox plates are the same size and have a large radius at the top corners. I drilled a 5/16" diameter hole at the origins of the two circles and used these as pivot points on the rotary table. I also machined a small radius to the outer edges using a router cutter so that I dont end up with a sharp corner inside the flanges.



Two other formers were made at this time, one for the front tube plate and one for the backhead but the one for the throatplate was made once I had the outer wrapper shaped. The second hole in each former gets used as a means of stopping the work rotating about the pivot by clamping to a tee-slot.



I decided to make the front tubeplate first using a piece of 3mm copper. I roughly cut out the shape, then placed it between the former and a solid backing plate and held it in a bench vice. Then it was a case of some firm tapping followed by annealing at red heat and plunging into cold water. The plunge isn't strictly neccessary as the copper goes soft anyway but it flakes off any scale and speeds the job up. It took two annealings to get this far.



I was cutting off surplus waste with a hacksaw as I went but it was getting more difficult to keep the shape the further round it went so I used the lathe to trim it down when I was about ninety percent of the way there.



Once I had the copper firmly on the former all the way round, I then skimmed the O/D  and faced the back. The only way I could find to hold the tubeplate was with my 4-jaw SC chuck because the 3-jaw wouldn't go down far enough. I turned it to about 10 thou oversize, then trimmed it to length using a left-hand tool.



The barrel was then returned to the lathe and mounted in the home-made fixed steady so that I could bore it to fit the tubeplate. It needed to be 1.1/2" deep to allow the plate to sit at the correct depth. I only use those super-sharp polished carbide tips for turning copper because ordinary tips tend to be useless with soft materials.



By having a small shoulder, it also means I didn't have to use any fixings to hold the tubeplate in place at soldering time, gravity did the job for me. At this point, it's a nice sliding fit but it will probably become distorted during the various  operations between now and then so will needs tweaking at the time.



Then it was time to put the holes in and this was done on the mill using the DRO to locate them all. I used an 8mm drill to start with, then followed with a series of slot drills to get the holes to size. The 10mm tube holes needed the reamer run through and the superheater tube holes were bored but the three remaining holes were just left at whatever as the bushes will be turned to fit. Offcuts of tube were used as gauges.



Firebox endplates next.

Regards, Steve

Jo:
You are making it look easy Steve  :Lol: It takes a lot of bashing to get the smokebox tube plate to turn into a dish. Out of interest what type of hammer did you use? We had a discussion the other day to see what people used and it ranged from use a wooden mallet, plastic, through to good old engineers bashing hammer and a few in between   ::)

That tip seems to be cutting the copper very nicely  :)

I haven't tried the Cadmium free Silver solder (yet) so I will be interested to see how you get on with using it.

Jo

springcrocus:

--- Quote from: Jo on January 27, 2023, 09:23:58 AM ---... Out of interest what type of hammer did you use?

Jo

--- End quote ---
Nothing special, just the nearest one to hand, usually a 1lb claw hammer. Like I said in my intro, knife-and-fork merchant.  ;D
I can't afford any of those fancy planishing hammers.  :'(
Regards, Steve

Kim:

--- Quote from: Jo on January 27, 2023, 09:23:58 AM ---You are making it look easy Steve  :Lol: It takes a lot of bashing to get the smokebox tube plate to turn into a dish.

--- End quote ---

I'll say!  The boiler I'm currently making is simple compared to what you're doing!  I've only got 3 tubes instead of the multi-dozen you have.  You're just making it all look so simple!

And yes, I used soft faced hammer (plastic head).  It's a cheap one from Harbor Freight that I've had for years. But it worked. Supposedly didn't mar up the copper, but clearly you had no problems with the claw hammer! You made it work quite well!

I'm certainly enjoying seeing how you did this!  :popcorn:
I've got a lot to learn!

Thanks for posting!
Kim

Mcgyver:
Nice work.

What radius did you put on the former, and what gauge copper?   Just trying to get a sense of what works.

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