August 21, 2014
A welded aluminum oil tank extended the life of a Formula Ford, making it race-worthy again.
Recently my friend Sam Smith, the executive editor of Road & Track, acquired an old Formula Ford to step up his track-day game. Overall the car was in really nice shape, but one of the issues that quickly popped up was a crack in the top of the oil tank. It’s a hard-mounted tank, so it was kind of expected that this would happen at some point.
As I’ve written before, aluminum can be problematic, especially in tank form. In this case, the porous material had been subjected to oil for years. And we all know clean aluminum is essential for a decent weld. This juxtaposition makes old aluminum tank repair, uh, fun.
Sam first was thinking that perhaps the cracks could just be welded shut, but upon closer inspection it was clear that the compromised section needed to be replaced.
One factor complicating the repair was the mounting tab. The tank fit pretty tightly into its space, so location would be critical. I didn’t have the car in my shop, so tacking it on and test-fitting wasn’t an option. This meant getting decent measurements before chopping it up.
I pretty much just sketched a few views that would hold the dimensions I needed. Some measurements were redundant, but that’s a good way to double-check locations, or to have a backup if one edge ends up being different than the original.
The tank was an odd shape. I clamped it to my bench firmly, evening out one side with 1-2-3 blocks before taking a cutoff wheel to it. Anytime you’re chopping up a piece to repair, err the cut to the side that will be discarded. After the bad section was out, I cleaned up the edges with a Scotch-Brite™ wheel. Some of the old weld actually peeled right off! That’s a serious lack of penetration.
Once the “old and busted” was removed, I used it as a template to cut the “new hotness.” Tacked it in place, then welded it, and then it was time to make the tab.
The old tab had been “repaired” several times. I just used a piece of aluminum angle and laid out the holes with the measurements I took earlier. To get a pretty exact point, I use sharp tungsten as a scribe, and often I darken the area with a Sharpie® before I scratch it, so I can see it more clearly.
With the holes drilled, I then laid out the lines where the edges of the tab would go. I double-checked some of the hole-to-edge and hole-to-surface measurements and then welded it down.
The next day I took it to the R&T garage, and Sam put it in. It fit like a charm. Also, he raced it the next weekend, and the motor didn’t die or blow up. I love it when a plan comes together.