Rear steelwork.

July 29th, 2012

This weekend I marked out some of the rear steel work. To make a template for cutting out the firewall I used some think ply and made a wooden stand to hold it at the correct 15 degree angle the rear firewall needs to sit at.

IMG_2669_1 Firewall template.

The rear firewall will have a flange around the edge which will rivet though to the aluminium skin. The flange needs to be flush with the inside of the skin. To find out where that will be you use sticks again. The template is cut smaller than the inside of the frame. A flat stick is then laid along the frame and clamped to curve to the shape of the body. Using another stick with marks on it you draw a line from a fixed point on the template (I used a point 6 inches from the floor on the centre line) along the stick, one end of which butts up against the inside of the long stick along the frame. You then make a mark a fixed distance back from that point (I used 2 inches). By doing this in multiple points around the frame you end up with a series of points on the template that match the curves that the skin will take by a fixed distance away from it.

You then remove the template and using your lines and marks extend out the points the amount you previously pulled them back. That gives you the line the skin will follow. You then add on the flange width to that and cut it out. It is easier to understand with pictures.

IMG_2678_1 Short stick from a fixed point to a long stick following the frame.

IMG_2683_1 After marking the template you transfer the points back out on the steel.

IMG_2684_1 Close up of the points.

I need to join up the dots smoothly on the steel still. I will get something suitable to trace around to get a smooth curve.  Some of the points are slightly out of line with each other but no more than 1/8th of an inch. I think if I can get the firewall correct I can then tweak the steel frame to make up for any differences.

IMG_2690_1 Firewall marked out.

I also marked up the front two side panels on each side of the car. The rear most one will be made later as I need to work out how I will cover the springs cut out once the rear firewall is in place.

I also marked and cut out the steel for the tunnel over the rear axle. I am making it in one piece then will cut out the appropriate relief for the top of the different housing and make a separate cover for that later. I want to bend and weld that top the firewall first so it all remains straight and rigid. It is an odd shape since the body tapers front to rear as well as sides not being vertical (by design!).

IMG_2682_1 Rear axle tunnel.

I will get the front two panels of the sides in place as well as the firewall and the tunnel over the rear axle. Next I can do the side panels of the axle tunnel. Then the section of side in front of the firewall with whatever is appropriate for the spring cutouts. Finally I can make the transmission tunnel that runs down the centre of the car from the gearbox to the rear firewall.

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