Building the "Lilly Belle" Boiler

[Michel Richard]

What pressure are you building to ? i.e. operating/safety pressure and test pressure
Thx. I'll be following this thread closely !

[gwrdriver]

100psi Working pressure (WP)
200psi Initial hydrostatic test pressure
150psi Subsequent hydrostatic test pressure
115psi Initial steam test pressure

[Builder01]

Yes, thanks for the photos and boiler stats. This is good stuff! I am a decent machinist, but I know very little about boiler making.

[gwrdriver]

Installment-05a Throat Sheet Forms & Forming

The fairly complex forming needed for the firebox end of this boiler required some careful thinking through and planning to insure the allowances mentioned in Installment 02 were provided for. Ending up with a bit too much to trim off is far better than coming up short, which would be fatal. As we all recognize, from time to time there is more work involved in making the forms (jigs, fixtures, etc) than in making parts themselves. Such is the case here.

Two formers were needed to form the throat sheet, a male, and a female, and for these I used 5/8" hot-rolled steel plate because the target flange depth was 1/2" and formers need to be thicker than the depth of the flange. The reason I used steel, rather than say Oak, was that the female form would have to endure a considerable pounding on its I.D. (in tension) and I didn't want to have to have to bother with a broken former. I started with the male former which was a steel plate blank rough-sawn to size (Photo 001), machined (Photo 010 and 011) radiused, and dressed smooth (Photo 012).

The female form (Photo 013) was also of 5/8" steel plate, bored, and radiused so as to form a generous fillet in the barrel flange.

This was also left over from a previous boiler project and frankly I don't recall how I rough-cut the center hole, but do recall it was no joy. The copper blank (Photo 003) was annealed around the center opening and sandwiched between the two forms. (Photo 014) At this point accurate aligning of the two formers and the copper blank became critical, the symmetry of the boiler depended upon it. Since there was no way to pin the two formers without penetrating the copper blank, alignment was done using scribed register lines.

[gwrdriver]

Installment 05b - Throat Sheet Forming

To begin forming, the copper blank is positioned and the male form is used as a backing plate to keep the copper blank flat while the inside flange is raised. The inside flange is slowly raised by first picking the edge of the copper with a thin bladed screwdriver. I continued raising by tapping thin hardwood wedges under the copper, working them all around, followed by a thicker hardwood wedge. I anneal again at this point and switch to hardwood sticks with wedge cut ends which are hammered all around to raise the flange further. (Photo 015)

The process is repeated until the flange is fully layed over. (Photo 016)

To finally finish the flange I.D. I used a short piece of 2"+ diam steel bar placed inside the open hole as a hammering "dolly" and working around the opening I snugged the copper tight to the former hole.

To complete forming this head the male former was turned over and the outside flange was hammered in the usual way, annealing as necessary, using the female former as a backing plate, until the flange was fully laid over. (Photo 017, 018, 019)

The formers were then used as jigs to hold the head for machining and the overall result was excellent and exactly what I was trying for.

[shayloco]

This is a very interesting series of posts. Please keep us updated. Documenting as you go is a lot of work but is much appreciated.

-Larry

[gwrdriver]

PS - The final finish on the head pictured, as will the surfaces on the heads, was produced by burnishing with a 3M Scotch-brite VF abrasive wheel.

[Benjamin Maggi]

That sure does clean up nice!

[Bruce_Mowbray]

Harry,

Just curious why you didn't use a slope sheet? Original plans or personal preference?

[gwrdriver]

Bruce,
The owner wanted to preserve the original shape of the boiler.