Tinsmith's in frame gas tank for cantilever Schwinn.
Ever since I saw Bairdco's first copper gas tank I have wanted to make one. I have some experience with soldering and am encouraged to go ahead and try it from past success in making juice can gas tanks. With those it was just soldering a copper filler and gas outlet to a tin can, so most of the skill involved had more to do with the leather covering stitched on than in any real fabrication.
I knew an in frame copper tank would be a whole new ball game. My friend Tinsmith kindly offered to help and share his shop with me. His own gas tank experience is limited to a steel in frame tank he is just finishing up for a stretched industrial worksman project ((awesome bike), but he has many years worth of tin smithing knowledge and figured it might transfer over into making something out of copper. I'm grateful for his help.
The bike I want to make a tank for is a 53 Schwinn with a cantilever frame. My current ride this winter is a 51 cantilever Schwinn and I want one for it, too. I don't weld, so that's why I am interested in copper, something in reach for the rest of us. Besides, I think they look cool. Copper is the poor man's gold.
Tinsmith (Dan) suggested we make a prototype tank out of tin since it is less expensive than copper. The first photo shows a sheet of electroplated tin, which accounts for the shiny finish. A cardboard template was scribed onto the tin and cut out with tin snips. The slightly burred edges were passed through a rolling machine (not shown) to flatten out the burs and smooth up the edge. This could also be done with a file.
His plan was to make flanges on the side pieces to give a surface to solder the top and bottom to. To make the flange, which I believe is 3/16 of an inch and is at a 90 degree angle, he uses a specialized tool called a burring machine which is operated with a hand crank. He passes this through several times, bending just a little bit with each pass. Each time stretches the metal a little at a time. There is skill involved in this, applying just the right amount of hand pressure... try to bend too much in one pass and the metal will kink. So, even though a machine helps make the flange an even 3/16", a keen eye, an understanding of the material and light touch are in order.
Dan had already made a kind of wooden template which I will show better in photographs with the next post. It follows the contour of the side pieces and gives him a solid form to tap the tin against to get an accurate 90 degree bend in the flange. Again, he is slowly stretching the metal, a little at a time, as there are complex curves involved. A more linear tank would be simpler to make, at least out of tin or copper.
He tried a test fitting at this point with both sides cut and flanged and with the top piece of tin held in place. Looking good! I'm already beginning to think the tin version may be just as good as the copper. I was surprised and pleased at how nice it looks, almost like a chrome tank. It could be clear coated with Top Flite, the gas resistant paint 2door has recommended or it could be painted. I can see a nice decal on there with clear coat maybe.
Tinsmith, please make any comments you wish to correct me or clarify anything I have said here. And thank you for sharing with all of us your skill and love of tin work. It may be a couple weeks before we have another shop session. Dan has a job and also a very cool 4 stroke Worksman project. Maybe he'll let me open up a thread on his project to share that, too. Thanks, buddy. See you in a couple weeks!
Someday when I grow up I will probably lose interest in toys with wheels, but until then...