The old tanks are made of brass but the design is faulty.
JohnG's tank was split up the side, starting at the seam, from flexing. So, it wasn't the solder that let loose, but the tank itself.
As the tank pressurizes, the structure tends to deform into a sphere (a ball), peeling the middle seam back each time. This happens because equal pressure is exerted on all inside surface areas simultaneously. That means, if the top shell (~4"x6") sees 13-psi, then 24"sq. x 13psi =312 pounds of pressure and the bottom sees an equal 312 pounds. This increases dramatically if your radiator cap is a higher psi rating (new cars use 19psi caps). It's no wonder why these tanks leak over hundreds of heat/cold cycles.
Later model tanks featured 'ribs' which helped but didn't solve the problem. After careful examination and thinking about the design, one haunting question remained, 'how do I stop the flexing'?
I drilled three thru-holes (top-to-bottom) and soldered solid silica-bronze rods in place using close-fitting brass washers at the ends to distribute the surface area. Then I re-tinned the seam and damaged areas, and replaced the lead with silver-bearing alloy (mostly antimony and tin) which is 30% stronger than lead. No more bloating, and the seams are much happier with far less flexing. I'm showing as much reality as possible so I did not paint this tank:
(CLICK ON THIS PICTURE to see the whole web site.)
I leak tested it and sent it back to John many months ago and I haven't heard anything negative since. - Dave
JohnG's tank was split up the side, starting at the seam, from flexing. So, it wasn't the solder that let loose, but the tank itself.
As the tank pressurizes, the structure tends to deform into a sphere (a ball), peeling the middle seam back each time. This happens because equal pressure is exerted on all inside surface areas simultaneously. That means, if the top shell (~4"x6") sees 13-psi, then 24"sq. x 13psi =312 pounds of pressure and the bottom sees an equal 312 pounds. This increases dramatically if your radiator cap is a higher psi rating (new cars use 19psi caps). It's no wonder why these tanks leak over hundreds of heat/cold cycles.
Later model tanks featured 'ribs' which helped but didn't solve the problem. After careful examination and thinking about the design, one haunting question remained, 'how do I stop the flexing'?
I drilled three thru-holes (top-to-bottom) and soldered solid silica-bronze rods in place using close-fitting brass washers at the ends to distribute the surface area. Then I re-tinned the seam and damaged areas, and replaced the lead with silver-bearing alloy (mostly antimony and tin) which is 30% stronger than lead. No more bloating, and the seams are much happier with far less flexing. I'm showing as much reality as possible so I did not paint this tank:
(CLICK ON THIS PICTURE to see the whole web site.)
I leak tested it and sent it back to John many months ago and I haven't heard anything negative since. - Dave
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