Firewall flange.

February 25th, 2012

Today I hammered over the firewall flange. I started by clamping the firewall to the car and using a little jig I made to draw a line in the correct place on the steel. I had already drawn a line when I measured the firewall up but that was before we bent it so I wanted to redraw it on the car.

IMG_1690_1 IMG_1699_1 Marking gauge.

The jig is just a  piece of wood with a slot cut in it. I then taped a Sharpie marker to it so the marker would leave a line the correct distance below the top of the hoop. The correct distance measuring is 2.7mm. Close enough to 1/8th of an inch so I used 3mm. Yes, I mix measurements a lot on this car!

With the first line in place I then drew another 15mm higher so I knew where to cut the steel.

IMG_1703_1 Lines on steel.

As it happened the line I drew was within 1/16th of an inch of the original line drew on when I measured the steel.

I then started to fold over the lip. I am not going to describe this in great detail as I did it wrong! I did a test piece first and that came out OK.

First I started knocking up the edge on my steel plate using the borrowed bench stake. As you do this you need to break the edge. This means putting in a definite bend right on the line you want. I didn’t quite do this on the main firewall. I must have fluked it on my test piece. As you hammer the metal up the top edge puckers since you are trying to force the metal into a smaller curve.

IMG_1692_1 IMG_1694_1 Folding the lip up.

To remove the puckers you need to shrink the steel. To to this you heat it up then hammer it down which shrinks it.

IMG_1695_1 IMG_1696_1 Heat to remove puckers.

You then dress the lip with the hammer and dolly. My test piece didn’t come out too badly so I felt confident to go onto the firewall.

It started OK but I don’t think I broke the edge properly. Then when the puckers formed I lost my line and it started going wrong as I was trying to hammer them out. Luckily then Joss turned up and showed me how to do it properly.

It is very difficult to describe the technique and Joss is an expert so when he does it he does it fast and makes it look easy. The other thing he did was use pliers to bend up parts of the flange and put twists into the steel. Imaging bending a flange in tin foil. When you bend it at 90 degrees you would have too much metal on the top edge. If you bend crinkles into that edge you can make your fold still but you end up with the lip all wavy. That’s when you use the heat to shrink the folds into themselves. Hard to describe and I never thought to get photos.

Anyway, with Joss helping (well doing most of it) the flange was done. I just tidied it up a bit and then trimmed it down a little to give a nice edge. It fits pretty well. And with the rubber strip there to hide all sins it should be fine. Minor adjustments can (and probably will) be made later.

IMG_1704_1 IMG_1706_1

You can see how the aluminium skin will wrap around the front hoop. The rubber strip attached to the flange and covers the gap between the bonnet and the scuttle.

Next the valences.

Oh, and she must be starting to feel like a rear car since I already have an oil leak!


Oil leaking already!

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