More Boiler Progress

[GWRdriver]

After slowing to a crawl for a while . . . I like to build my boilers around solid (or near solid) wood firebox forms, both inside and outside, for two reasons. #1 is that copper will try to "escape" being formed and a solid form will prevent the wrappers from puckering or buckling (escaping) inward when wrapped around the head profile. #2 is that the forms, when made square and parallel, insure that the entire firebox end is square and aligned to very fine limits. Both inside and outside "boxes" will be assembled competely and temporarily screwed/riveted together around the forms insuring squareness.

At left is the finished inner firebox form with the heads in place ready for the wrapper. The box on the right is the raw outer firebox form awaiting squaring and sizing, which I do by flycutting.
http://i6.photobucket.com/albums/y226/gwrdriver/FORMS10A.jpg
This wood form excercise is a lot of work, a LOT of work, all for a forming process that takes maybe 30 minutes per wrapper, but I find it's more than worth the effort to insure the plates stay dead flat during wrapping and that the boiler alignment is virtually locked in. The inner laminations are common pine construction scrap and the outer layers are poplar which is a semi-hardwood and machines well.


[This message has been edited by GWRdriver (edited 04-04-2006).]

[Jan-Eric Nystrom]

Thanks for that photo and idea! I sure will keep it in mind!

Greetings,
J-E

[EARS_MCFLY]

It's looking good, Harry!

[GWRdriver]

J-E,
The above pine wood isn't seasoned so if you use this method be sure to let whatever wood you use acclimate itself to your workshop. I glued these up and let them season for a couple of weeks but I still got a bit of movement when I started milling them to size.

[phty95014]

Hi Harry,

Thank you for sharing your considerable
knowledge with those of us that have yet
to master the art of boilermaking. I like
the wooden forms idea and would not be too
much work if one is building a stable of
iron horses with a similar family
resemblance.

More tips please!

Pat Y

[GWRdriver]

You're welcome Pat. Interesting you should mention the "family resemblence" concept.
I actually had something along those lines in mind when I designed this boiler.
It could have looked different in external appearance but I thought it very
possible that somewhere down the line the formers might be needed again so I made it a
"generic" wide firebox Belpaire design where the barrel is a standard (US) 6" copper tube
6.125"od) tube, the water legs are 3/8" all-around, and all sheets & plates are 1/8".
With all those basic widths and diameters set, the lengths (barrel, flues, firebox,
(etc) and bushing penetrations can then be varied to suit a wide range of applications.

I suppose to make it a full kit I should do a set of alternative plates, or at least drawings,
for a narrow firebox version.


[This message has been edited by GWRdriver (edited 04-04-2006).]

[fred v]

several years ago i bought the book on building a 1/2 size traction engine. the boiler shown was a riveted boiler and he hammered out the shapes over a steel form just like doing copper. WOW what a job that would be.
fred v

[GWRdriver]

Fred,
In our cultural/literary history, when various stereotypes for things that were found in "towns" were portrayed, the "boiler works" was always portrayed as the noisiest place in town. We don't need to guess why.

[pockets]

GWRdriver,
Thanks for the great technique.

Greg B.

[GWRdriver]

Here's what the formed plates look like when they're scrubbed up.
These plates came out of annealing and forming process with an unusually tenacious
oxide coating, which you can clearly see in the photo above. I knew this would defy
pickling so I took it off with a Scotchbrite wheel in an angle grinder. The sad thing is,
before long all that prettiness will just be chancred up again by silver soldering.
http://i6.photobucket.com/albums/y226/gwrdriver/PLATES.jpg


[This message has been edited by GWRdriver (edited 04-05-2006).]

[Unka Jesse]

Lookin' great as always Harry. You gonna bring any "progress report parts" of the TICH to the MSLS meet?

Unka Jesse

[GWRdriver]

Jesse,
My goal is to have at least the external shell completed by the meet and if I keep at it I could have that and maybe a bit more done.
That may or may not happen though, lots to do besides boiler work between now and then.

[Alan Stepney]

Harry, wiv a bit 'o practice you could get quite good at that. lol !

Seriously, I have never thought of, nor seen, the idea of making the firebox forms as a box.

Excellent idea.

[GWRdriver]

Alan,
The benefits of taking this extra measure became apparent while building my first boiler, a 6" diam copper with straight firebox, about 1970. The firebox heads were cast bronze, rather heavy, and about the same size and shape as the firebox I'm building now.

I assumed that when I went to form the wrapper, which IIRC was 3/16" sheet, I could do so by using the two heads as forming guides and bend the wrapper over them. Wrong! Things were fine over the heads themselves, but between the heads the copper wanted to take the path of least resistance and took on a distinct concavity or swayback where it rounded the shoulders and the crown area. By reheating and reforming I managed to work some of the swayback out of that wrapper but much of it remained.

From that point on I have always made solid formers for shapes which might cause the copper to try to escape the forming process and take on shapes that were never meant to be and I found this saved time and nerves in the long run. This became more useful when I began doing an occasional boiler for beer money where having to remake a major part would be quite costly extra time and materials, and I'd have to absorb that cost.

[tel]

You're more'n just a pretty face Harry. Like AJ, I've never come across that way of doin' 'em before, but I LIKE IT

[phty95014]

Harry,

You must drink some pretty rich beer if you
trade boiler making time & parts for it!

But on a more serious note, do you use the
forms as you start to braze the boiler?
If so, how do you prevent the wooden ones
from burning?

Pat Y.

[GWRdriver]

Pat,
What I do is use the wood form just as a tailor or seamstress would use a dress form. I make the form the exact shape and size of the ID of the box I want to build, making allowances for material thickness, flanges, seams, etc, and I fit the firebox plates over that form. The block also acts as the former for the wrapper sheets so I actually end up beating on the block a little bit, but not enough to hurt it.

Initially I use a few small strategically placed brass screws (#4-40) to hold it all tightly in position on the form. These are threaded through the wrapper into the flanges. There is a great deal of cutting, fitting, trial assembly, disassembly, then RE-assembly in this work but once all this is done and things are fitting as they're supposed to I disassemble the plates and remove the wood form. I then reassemble the firebox one last time with the same screws and one by one I replace the screws with copper rivets which as often as not are simply snips of copper wire peined over. Everything stays exactly in place during the process.

Then I pickle, flux, and solder it up. During the brutal thermal experience of soldering things always move so you never end up with exactly what you started with or exactly what you wanted to end up with, but it usually comes out close enough so that whatever changes have taken place can be accomodated in subsequent construction.

There are a lot of tiny little things I do along the way to help the process, most of which have to do with one of two things, help the solder flow into all the places you want it to flow, and improve water circulation within the boiler.


[This message has been edited by GWRdriver (edited 04-06-2006).]

[Bill Shields]

Harry has done a beautiful job of helping to show everyone just exactly how much work building any type of boiler is...especially one of copper....and doing it RIGHT!

So the next time someone asks what you think is too much $$ to build a boiler.....think again.