Gas Tank Mount Rework 2

So I was not real stoked to do my final mock-up of the mounts and tunnel o then figure out the mounts were designed to be flush with the inside of the tunnel and not the outside. That would have required cutting a complex shape into the side of the tunnel. Not real easy with a cut off wheel and carbide burrs in U shaped sheet metal. So I have to whack off another .100" of material.
Curve in the mounts fit perfect to the tunnel. Grabbed all of the big C-clamps that I could find, held everything flat to the table, double checked the alignments of the mounts to each other, then tacked it together. Each mount got 4 tacks. The inside 'windows' in the tunnel will be cleaned up to the mount profile and welded from the inside, once tacked into the tank. I want to tack everything into the tank before finish welding. Hoping it will minimize the amount of twisting and warping that can happen. I was SO happy that the tunnel assembly and mounts fit like a glove on the frame. I could have not hoped for a better outcome. In case you are wondering, the last 2 pics are from my office at work. Yes, I have a disassembled motorcycle in office.

Tunnel Layout

Chad is helping me out with finding the aesthetic centerline of the tank. Then transferring it to the bottom to layout the tunnel and mounts pockets. A lot trickier than it sounds. The stamped, then hand formed tank halves are anything but identical, so the conventional ruler layout method won't work. I was working on cutting the tunnel down to final height. Fab Kevin hooked me up with this piece. 13ga, cold rolled steel. Strong, precise and great to work with.

Gas Tank Tab Karate Chop

First set of flat stock tank mounts going in the garbage. First thing I ever tried to TIG weld, not the best welds, and pretty easy to cut off. Live and learn. Smooth frame, to fit new mounts on.

Gas Tank Mount Rework 1

The best laid plans are still subject to change. Original tank mount pockets were with a 1" wider and slightly longer tank. The flanges were wide, and the walls thick. I was building a tank that could double as an anvil. The .150" walls were machined down to .080", flanges changed the same way. Easier to weld as less heat is needed. The more heat put into the 16 ga bottom, the more likely it gets brittle around the weld, and wants to crack in the future. Rear mounts (the smaller ones) used to be the real long front ones. I re-purposed them, cut .070" radially off the flanges to decrease the width. I want to push the mounts as far to the back as possible, but also want to the flange to bottom weld to stay at least 3/8" from the bottom to tank sides weld seam. Made the simple fixture and knocked out the pockets. The rear mounts where just clamped into the vise, double checked for flatness with the digital protractor (one of the best $100 tools we have in the shop) and knocked out.

Tank Bottom

16 ga cold rolled steel. Bottoms of the tank are rolled over 90 degrees to help the bottom lay flat. A straight butt joint of the bottom to the sides would be a weak way to go over the long term. The repeated vibration and resonance that the tank will go through on the shit box Michigan roads will rip a butt joint. A lap joint is much stronger in this case. Won't smooth out completely flat, but that doesn't really matter. A skim coat of filler will fix that. I want to grind as little material away from these welds as possible.

Weld Up Gas Tank, Top

Welded up the top of the tank. Jumped around welding no more than 1" at a time. Held the torch over each weld until the post flow tapered off. Tank never got so hot that I could not rest my hands anywhere on it. Very minimal amount of warpage, especially considering how much stress in the original stampings and how much shape/ stress I added.

Getting Tacky Gas Tank

Tank going back together. Tack, hammer seam tight and level, tack over here, repeat.