| HI
Now the wrapper sheets are cut the fun starts.
Copper work hardens and work hardens very fast just a few movements on a copper sheet that has been annealed is enough to get the copper to a point that it wont bend easily. Once its hard it must be annealed, annealing copper is easy just bring it up to cherry red with a good propane torch hold it there for a few seconds and then let it cool.
There are different schools of thought on quenching copper after annealing. Some will have it that air quenching is the only way and keeps the copper workable for longer. Others swear by water quenching also pointing to the way the black scale drops off in the water quench.
As far as i can tell the only advantage to water quench is the speed you can start reworking the copper. The scale isnt much of a problem just turns your hands to a colour your wife wouldnt want on her stockings.
No matter what you use the sheet will need a lot of heat put into it to get it to cherry red. I use a large propane burner and a half pint blow lamp in addition on very big sheets.
Big word of warning on wrapper sheets, Dont use a hammer to help the bending! if you need to form a tight bend use a rawhide mallet or a block of pine side of teh grain on the copper. Copper in its soft state marks very easily and it looks like hell on a finished boiler if its full of dents and dings. Ok OK a set of sheet rolls would be the best way but 10 gauge wants some hefty rolls and not the ones you get from Chronos for 90 quid.
before you start set out any forms your going to use. For a wrapper this is as a rule just a stout lump of steel bar to form the bend round. On a more complex boiler wrapper a few odds and sods of 1/2 inch 78 and one inch bar will help. If your really fussy a wodden former can be made to the inside curve of the wrapper. To be honest this only really helps in checking the shape.
Pictures are pretty much plain to see so il spare you all the words.
I think from the picture of the wrapper being draw filed youl get an idea of the amount of copper in this one and the heat that’s required to anneal it!
first of many burns on this one, interesting how skin fizzes at 500 degrees almost like bacon cooking! Hmm bacon sandwich sounds in order!
Cheers Kevin |