Yarrow boiler investigation

[DJoksch]

I’m collecting material to build a Yarrow boiler with a 3” main tank. If I used domed tanks, I can’t get to the inside of the rivets. I‘m thinking hard solder and maybe something like this pic I found.

 

[DJoksch]

I came across 2.5” pipe at 0.067” and 1.25 at .053”. I have some 3/8” type k possibly for the return tubes. I need to measure the wall thickness when it arrive. I’m aiming for another 50lbs boiler that I will likely run at 35.

 

[DJoksch]

I am planning on domed end caps so riveting is not the plan. Rio Grand sells a 1207deg 65% silver solder that should do the job. I’m working up the dimensions and determining the max safe working pressure. Will provide sketches shortly. The 3” fire tube project worked out nicely.