Advice on Brazing the Barrel Joint - 7" OD Copper

[joeburgard540]

Thanks everyone for the advice.

GWRdriver - Thanks for the idea of putting a few small external straps. One large butt strap to cover all the teeth would have to be about 1" wide. Then there are the issues of ensuring proper joint gap over the entire length (~17"), avoid trapped flux, etc. I'll keep the trick of adding a feed hole to large lap joints for future use.

Regarding the cadmium bearing silver brazing alloys, two things. First, since I already have about 10 oz of the BAg-1 alloy, I'm not going to break the bank to buy a different alloy at this point. Second, I installed an exhaust fan that moves 530 cfm of air directly over my brazing hearth to mitigate the fumes. So far the fumes from the flux have proven more irritating, but this was my own fault due to the temptation of looking directly over the part while heating it with the torch.

TIG welding is a possiblity (one of my welding instructors offered to do it), but there are issues with welding copper that is not oxygen free (pitting, porosity, and brittlness around the fusion zone). I do not know what the copper alloy is, but assume it to the most common C110 ETP copper which is not good for welding.

I'll clean up the teeth and file them to fit better. Will also try planishing them a bit to squish the metal and close the gaps, although I don't expect to carry this to excess (like the gap of 1/16").

I'm still a beginner at silver soldering/brazing and am currently making practice joints out of 1/16" sheet: Lap joints, tees, tubeplates, etc. You can only learn so much from books until you have to just do it hands on. My thoughts are to screw up practice or scraps before starting on the expensive projects. I highly recommend the AWS "Brazing Handbook" as a resource, the 4th Edition, 1991 can be had for relatively cheap ($15). Other great references I have are "Model Boilermaking" by K.N. Harriss, "Model Locomotive Boilermaking" by Alec Farmer, "Model Locomotive Boilers: Their Desing and Construction" by Martin Evans, and "Soldering and Brazing" by Tubal Cain.

John,

Yes I'm active duty Army at Fort Hood. XO of an Armored Company of the 1st CAV Division.

Cheers,
Joe

[gwrdriver]

Joe,
Everything in the process is important in order to end up with a good silver soldering job, but the two most important things are proper preparation and sufficient heat. INsufficient heat is probably the most frequent cause of poor results or failure. You can't have too much heat at your disposal. You can apply too much heat, but you can't have too much at the ready. Best of luck with the boiler.

[Bill Shields]

Thoughts for future - from some things I have seen.

The finger joint that you show can also be made where the fingers OVERLAP the main barrel so that you have surface contact between the inside of the finger and the OD of the barrel. This eliminates the need for the extra band Harry suggested.

Is the extra band vs. this technique actually easier...probably - but knowing there are options is always fun.