21-23 Muffler Questions

[MikeW]

I am at the stage of fitting the exhaust system to my 21F restoration, using a combination of original and reproduction parts. I'd like to use the original muffler. However the muffler shell, which is otherwise in pretty good condition for its age, is partly detached from the inner brace/compartment-divider, The photos should show the problem. For 17-19 the muffler was bolted together along this seam. Two questions. First, what was the fixing method for these 21-23 mufflers? Spot welding? And second, as I don't want to blow a hole in the thin sheet metal with my unskilled welding technique, might high-temp silver soldering be an option for repair?
P1050037.1.JPG 005.JPG

[exeric]

I made the '15-19 mufflers and the baffle was riveted to the outer shell, or case for that vintage. The '20 and later baffle was spot welded to the shell from my observation. To preserve the remaining finish, you could lead solder the baffle to the shell using a heavy soldering iron, or a torch heated copper iron. More heat is needed for silver solder and that would discolor and change the finish of the shell. Regardless of what you use, the mating surfaces of the baffle to shell will have to be scrupulously clean to get anything to stick, and that is going to be hard part. You could also make some soft steel flush rivets that would rust up like the shell, and you wouldn't have to clean anything. . . . I think that's what I would do if it was my problem.

You can barely see the baffle rivets unless you're at eye level. This was the first muffler I made for my 1916F.

mufc.JPG

[T. Cotten]

I got pretty good with silver-solder, Mike!

My masterpiece was a solid stainless assembly, but the stress of duty soon produced microcracks, the bottom shark-fins blew off, so it went on the roof:

ROOFBIKE.jpg

Soft solder is more forgiving to shock.

...Cotten

[MikeW]

Thanks for the responses Eric and Tom. I very much appreciate the help and information I've always had from the forum. I agree that getting the metal chemically clean for solder (silver or soft) would be a challenge, and that the result might be prone to stress fractures. I'm left with a couple of options: rivetting- perhaps even with stainless "pop" rivets which, as Eric said, would be very hard to spot when the muffler is installed, particularly if lightly ground and painted. Or welding. I had thought about clamping the sheet metal together and giving the existing, fractured spot weld points a touch with my Mig welder on a low setting, but I have blown holes in sheet metal once before and was wary of that option.

The source of my reference to pre-20 mufflers being bolted rather than spot-welded was the Replicant Metals offering illustrated below. I know that one shouldn't assume that commercial reproductions are accurate (we all have our stories!) but I haven't had an original pre-20 muffler in my hands and Replicant has a reputation for accuracy.

Replicant 1917-1919 Muffler 2.jpg

[T. Cotten]

Eric suggested an iron for soft solder, Mike,

And I agree; Its nice to have a heavy-duty electric like this one on the right:
TANKTIN.jpg

Tinning is easier because there is no flame contamination, and far greater control; A punched disc of copper or brass over each hole can then be filled over and finished, as lead was the standard for all auto cosmetic dent-filling for generations.

...Cotten
PS: I'm old enough to remember when 'lead sleds' became 'bondo boats'.
(Not really.)