Several folks have asked for a progress update on the infamous "low-crown acorn nut" escapade from a few months ago, see: https://www.chaski.org/homemachinist/vi ... 8&t=110061
Attached are some progress photos of the firebox wrapper as of this evening: the throat sheet, side sheets, and backhead. As a reminder, this is a new-build of a 1.5" scale, 7.25/7.5" Boston and Maine K8b 2-8-0. This is my first attempt at doing firebox wrappers, and I have to give huge kudos to Jack Bodenmann and RussN (NP317) for the inspiration to do this. I first saw Jack do this on the original Berk (probably 15 years ago) and knew immediately I wanted to try to do the same some day, and the "exposed" backhead wrapper that Russ did on his Mikado was really slick. It could not have been a more fun and enjoyable project, and I highly recommend the techniques that Jack has shown us over the years. Thank you, Jack and Russ!
The wrappers themselves are made from 1/16" thick, fully annealed copper. 1.5" thick MDF forms were made (by gluing two 3/4" thick MDF slabs together), and I used a dead-blow hammer with soft rubber faces to "whomp" the sheets into shape. It works exactly as Jack describes, and the thrill of seeing a flat sheet turn into a wrapper is indescribable. Having never done it before and not wanting to chance it, I annealed the backhead wrapper about 6 times during the forming process using a Prestolite torch (air/acetylene). In retrospect, I probably only needed half of that. The throat sheet was done in 2 annealing steps.
I also now understand that another part of Jack's genius (beyond being able to make the parts that he does) is his ability to take pictures of - and explain - the exact steps in the process that you might get tripped up on if you try to do it yourself. On several occasions during this work, I had the "ah ha!" moments of enlightenment as I went back to Jack's threads on his various loco projects and inevitably found a photo that solved the precise fabrication challenge I had at the time.
I hope you enjoy the pics, now back to work for me!
Sincerely,
Adam
