copper boiler builders question

[ausdan]

May be the first of many question.... Have began the 1st steps in the construction of a replacement copper boiler for a 5" Don Young design Hunslet

Plans are with the Boiler inspector awaiting return..

1st part will be the boiler outer tube being 6" Dia (3mm copper)... if I were to have it rolled, will it need to be annealed before rolling. Or is mainly just the parts that are bent over a fairly tight radius (formers) that will a few annealing steps as it hardens as it is worked with a hammer or similar ?

cheers
Danny

will built under the Australian boiler code

[mutley]

Hi Dan
Why not use tube and save having the butt joint and strap? Depending upon how thick the plate is you may need to anneal it a couple of times whilst rolling. When forming the plates you need to anneal the copper at regular intervals. As soon as the copper starts to show any resistance then think about re-anealing it. Personally I now buy my plates preflanged and save the trouble.

[GWRdriver]

Dan,
I always try to use a hard drawn tube for the barrel and have so far been able to do that in all but two boilers I've built. In those instances, since I lack bending rolls, I had the 1/8" sheet rolled by somone else and it was done in the hard state. In both instances I also created a dovetailed/castellated joint rather than I butt & strap. Both of these choices are personal preference and I don't know of any reason why annealing the sheet first should make any difference except perhaps to make rolling easier if you have light or small bending rolls. Annealing might also alter the location neutral axis of the sheet, which would then affect the cut width required for a given diameter, but I'm not certain of this.

[ianengr]

Hello Danny,

If you wish to roll the barrel yourself, all you need is a solid wooden former, if you can't locate 1 solid piece like an old post or bearer large enough, obtain 4 pieces of timber at least 80 mm. square DAR - (Dressed all round) or have it dressed square on two faces and glue and clamp them together to make 1 piece a little longer than your barrel. Put it in the lathe and turn it to the size you need. You may need someone with a larger lathe to do this or a wood turner. If anything leave it a little oversize and take the time to face at least one end,

You will need to anneal it so that it dosen't spring open when finished and to get the ends of the plate truly circular and straight lengthways. Annealing after all forming is finished may help minimize unwanted movement and distortion when brazing. I would usually cut the plate to length using the mean Dia. giving 18.45 in. - 468 mm. for 6 in. O.D. If your cutting it yourself make sure you get it square before rolling it as its awkward to trim after wards. When you begin rolling have someone hold the former with the faced end down on the bench while you make the initial bend with the edge of the plate on the bench, this keeps the former and plate in-line. Remember to put the front or back edge of the plate on the bench so that you bend it in the right direction. (Murphy and his book of laws will be waiting to catch you out!)
and to protect the copper if you hold the barrel on its former in the vice to work on the joint edges.

If you have a "ring" type gas burner, put all your plates on it and anneal them together, stack a few bricks around it and put a piece of old sheet metal or similar on top to make a simple hearth, this makes heating quicker and more economical on gas. When forming, never hit the copper directly with a steel hammer or drift, try using a hard wooden block, a piece of nylon / hard rubber bar/mallet. The nylon bar is particularly useful, you can machine the dia. to suit the lower concave corners of a Belpair or similar style plate or face the end in the lathe flat to use on the straight flanges as a drift, its hard enough to get thick plate really flat without damage. Get rid of the excess metal on convex flanges such as the top of the Hunslet's backplate and throatplate and the top corners of a Belpair, as early as possible, this metal is being compressed when forming, the deeper the flange the greater the compression and thickening of the plate. This process takes a lot of energy and some people mistakenly feel they cannot close the plate completely onto the former to their satisfaction, repeated annealing and persistence and patience will bring success. The more annealing you do the better, it not only makes forming easier, the primary aim is to minimize structural damage to the plate itself.

If you have a milling machine, put the flanged plates with their formers on a piece of solid flat plywood on the machine table, put 1 or 2 clamps on the back of the former plate and trim the excess copper with an old slot drill or end mill etc. just above the level of the former, keeping the cutter on the inside of the flange, above the former and moving anti clockwise around the edge of the flange which must always deflect away from the cutter, moving the clamps as needed This is much easier than trimming with a hacksaw, although still a little tedious, it can be done 2 or 3 times during forming (before annealing) and leaves the plate edge well finished needing only deburring with a file.

I hope you find this information helpful.

Kind Regards,

Ian.

[Shawki Shlemon]

Hi Danny
Are you in Australia ? If you are somebody advertised in AME Sept/Oct issue selling copper tube including 6"dia . If you are building it to OZ code just follow your boiler inspector instructions and advice and you should be OK .

[ausdan]

thanks all for the information..I live in Adelaide, Aust.. We do not have a boiler inspector at our club for some time now and I cant see us getting one either...

Alot of members these days are building petrol/electric outlines, only a couple who are building steam are going with steel boilers, none with copper, (which is driving me up the wall, as they will tell you the pitfalls, yet none have attempted to build in copper)

that being said, our club doesn't have a large pool of steam engine builders and I need to rely on books, forums, email groups and the like to gather information

[Shawki Shlemon]

There are big clubs in Adelaide , we had the convention there last year and two years ago , how come you can't get a boiler inspector? Anyhow get a copy of the code , all details are in the code . I am a boiler inspector but how can I help from Sydney .It is not difficult to build a copper boiler.It is a matter of will and care .All the best for now.

[ausdan]

Shawki Shlemon, like I said our club is mainly diesel outline these days, not much steam, and not many steam engine in the wings...going by boiler inspector qualification listed in the standard, I might be the next chance in another 10yrs...as once I get this boiler going for my Hunslet, I will start one for the 7.25 Phamton....so for now we use SASMES inspectors....

I inquired about the 6" 1/8 by 36"copper tube, in the AME....Plus the postage would be $400AUD or more, though it would be quicker...I can purchase a 1/2 sheet of 3mm (900x900) for $540 which is more than enough for the complete Hunslet and some for the Phamton

Shawki, would you say it fairly common in Aus to braze the assembly's with different grades of silver solder, or rely on the heating at different stages so not to interfere with other assembly's and maybe just use a couple different grades..read its handy to leave the lower melt points to last for any minor touch up/ leaks

[GWRdriver]

Dan,
For what it's worth, 6.125" OD is the standard US tube size for 6" (nominal) seamless hard-drawn copper tube and is available in three wall thicknesses, Types K, L, & M. Type L at .140", or Type M at .122" would work.

[chameleonrob]

I don't know about the OZ code but in the UK it is advised at the very least that the boiler tube should be thicker than if seamless, by about 25% I think, throw in the cost of gas and solder etc. and the seamless tube looks more attractive.

rob

[havoc]

but in the UK it is advised at the very least that the boiler tube should be thicker than if seamless, by about 25% I think

Looks suspicious to me. Because the strenght of the plate is identical (drawn tube vs rolled plate) and you're going to make it harder to make a good joint.

[Shawki Shlemon]

In OZ the thickness required is the same . I agree with Rob after paying the cost of rolling (if you don't have rollers)and seam or joint ,the tube may be cheaper and neater . I did roll one for Rail motor 7.25" because of the odd size required . As for silver soldering , the recommended solder is 245 ie 45% silver, however 235 is allowed for step soldering as it melts at higher temperature . Normally once the silver solder has melted , next time it melts at higher temperature . I built 25 boilers and I only use 245 , I warm the boiler with heating burner , then use no 32 burner to do the task . Another thing I do is that I only silver solder a small area , clean inspect ( fix if needed ) then go to the next small area and so on .Rushing is not only slower but could end up in scrapping the boiler and this I am telling you from experience . I have rejected more than one boiler for this reason as it becomes unrepairable . Once the carbon gets in tight joints and can not be cleaned , it is impossible for silver solder to flow in .