So, on to the front fenders.
The fenders were stress-cracked where they had been bumped a few times and we wanted to add headlight pods Barbot style. Also, because we lowered the car, a bulkhead inside the fender kissed the tire at full steering lock. I knew I was in for a treat, not!
This first job was to patch the cracks, and here is where all hell broke loose. After sanding the rust and paint off, I tried butt welding the cracks. Every attempt resulted in severe and immediate blow through even with lowest voltage and speed.
I tried applying a copper backing across the crack to absorb the excess heat. Weld will not stick to the copper but that did not work. The only thing I can think of is that the copper has to have intimate contact with the steel and that is almost impossible with a curved fender. I just coukd not get it intimate enough – story of my life. I had made one hell of mess by this point and was tearing my few remaining strans of hair out. The project was in serious trouble.
In desperation I called André C who spent most of his career welding busted heavy machinery and is currently doing a magnificent total restoration of an MGB. So he came over and tried everything he knew and blew through quite a few times before he hit on a combination that worked. The solution turned out to be a bit counterintuitive. It was to do a push weld with 0.23 wire as follows:
- the tip at a 45 degree angle along the weld so the wire stickout was only 3/8″. This is the first counterintuitive bit. You’d think a longer stickout would be cooler.
- the edge tip of the gas shield actually touching the work piece, usually considered a no-no
- the wire pointing right at the crack, not slightly to one side.
- the shortest possible burst, just a mere blip
- voltage turned up just a hair from the minimum. This is the second counterintuitive bit, You’d think that a lower heat would work better.
- next tiny weld at least 1/2″ away from the first with a delay of 30 seconds for cooling between attempts. This bit was nothing new for me.
As you can imagine, it took forever to fix even a single crack, but it worked. It actually worked! Once there was only 1/8″ between welds I could relax a bit, turn the feed and voltage up, then fill in the gaps with little risk. I owe André a huge debt of gratitude. He basically saved the project.
We were trying to figure out why this was so bloody difficult and we have theories but nothing definitive. First the steel used for the car came from the Saar region in France and is notorious for its impurities. Seccond the metal is incredibly thin. Altough it starts out around 22 AWG, the steel undergoes a very deep draw while stamping the fender and stretches even thinner. Third, these fenders had been repaired once and ground, probably even thinner than original. Anyway, this turned out to be the welding challenge of the century. In the end I think I may have actually been butt welding the equivalent of 24AWG with MIG.
In the end I cut a huge patch from another old fender I happened to have lying around and butt welded it into place. It took forever, and looks a bit rough, but it worked. Phew! Yay Bondo!
The next job was to cut out and form the headlamp pods. I simply machined a ring of MDF the diameter of the headlight and with a Rube Goldberg set of rods and clamps, attached it to the fender right where I wanted the headlight to go. Then with bristol board I rolled a tube to fit the headlamp ring, and started trimming and marking bit by bit until the tube intersected the fender nicely all along its curve. Then I unrolled the bristol board and used it as a pattern for the metal tube.
I first hand formed the tube to fit over the MDF ring, then tacked up the seam of the tube. Positioning the tube was a case of measuring, adjusting, measuring, and more adusting, then tacking the whole thing into place.
The final job was to cut away the offending bit of bulkhead that was hitting the tire. I really don’t understand what its original function was in the first place. It didn’t add much stiffness and maybe acted as a primitive splash guard and rust catcher, so I took a risk and chopped it out. I guess I’ll find out its function the first time I roar down the highway. I’ll be sure to have someone follow me to pick anything that falls off.
Here is the end result. Mae West would be proud!