Supporting > Boilers
Calbourne - 5" gauge boiler
springcrocus:
--- Quote from: Mcgyver on January 28, 2023, 04:32:04 PM ---Nice work.
What radius did you put on the former, and what gauge copper? Just trying to get a sense of what works.
--- End quote ---
The copper barrel and front tube plate are both 10 swg (3mm) and the bore of the barrel is 4" diameter. I used a 5mm radius router cutter for the former edges.
Regards, Steve
springcrocus:
I've just realised that I forgot to describe the barrel before showing it being bored for the front tubeplate. :Doh:
The barrel is 4.1/4" outside diameter and has been machined to length by holding in the bore and supporting the other end in a steady. My steady wasn't large enough to use the rollers so I set some PTFE pads on the outboard ends of the arms and then reversed them. With a drop of lubricating oil, they worked fine. This isn't locked down yet but it shows the pad in place
Although it had been sawn reasonably square and didn't really need to be cleaned up, I faced about 20 thou off the first end. However, for some unknown reason, I ordered an overlong piece and decided to part the surplus off. The ring will come in handy one day. I cheated, though, I only parted about three-quarters of the way through then hacksawed the last bit before finishing the face with the parting tool.
More of the boiler parts have now been made including the firebox endplates and the backhead. These have all been melded around their respective formers and the workshop became quite hot with all the annealing that was needed. In case anyone has never annealed a piece of copper and was wondering how hot to get it, it's this hot!
Because the formers won't be needed again, they were used to support the work while the edges of the flanges were machined to size. The copper is still very soft at this time and will bend away from the cutter quite easily. I used a 1/4" diameter end mill to trim the edges, going round in a clockwise direction (climb-milling) to give the material maximum support.
The former was also used as support when I milled the endplates to length.
The firebox tubeplate was drilled in similar fashion to the front tube plate, the rear tubeplate has had the firehole bored to size and the backhead has been fashiond around another MDF former.
The tubes were expanded at the back end by about ten thou, then skimmed back to just under 10mm so that there is a tiny shoulder for the tubes to rest on when silver-soldering. Nothing is needed at the front because the front tubeplate will rest on the lip in the barrel. Some 6BA bronze screws were made and these have been used to fix the wrapper to the end plates. I don't like rivets for this because they don't hold the work firmly enough.
Also completed were the holes in the barrel for the forward clacks and the large steam-dome hole. The front tubeplate was used against the chuck jaws as a depth-stop and an MDF former bolted to a faceplate acted as the support for the other end. After drilling and reaming the two clack holes at plus and minus 90 degrees, the rotary table was set to zero and the big hole roughed out with a hole-saw before boring to size.
Once this was complete, with the rotary table still set at zero degrees, a scriber was mounted in a drill chuck and dragged along the full length of the barrel. I didn't do this on the Britannia boiler and had alignment issues because of it.
Regards, Steve
Jo:
What are you using as your pickle, Steve?
Jo
springcrocus:
--- Quote from: Jo on January 28, 2023, 06:38:43 PM ---What are you using as your pickle, Steve?
Jo
--- End quote ---
Citric acid. I bought a 5Kg tub of food-grade from Amazon for about £20 originally and it makes a dustbin-full of pickle.THIS is their current offering.
I use a damaged wheelie bin that the council were discarding.
Regards, Steve
samc88:
Nice boiler work, it all looks very neat
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