The frame is made from 25x25x1.5 wall thickness square section steel tubing and 3mm steel plate. In addition there are parts made from 25x25x3 mm square aluminium tube and 3mm aluminium sheet. The design for the basic steel parts, I think is fine, I am not so sure the rest is particularly elegant but it should do the job.

Basically, the frame comprises a top and bottom tube, each is cut and welded to form three slight bends to conform to the shape of the original bumper. These are welded onto two plates drilled to bolt to the left and right flexible fitting points. The frame is rigidly bolted to these points. (This should make the front end a bit stiffer at the expense of the theoretical scuttle-shake damping. Time will tell if this matters!)  The centre pivot is not used except as a body centre reference during construction..

Two plates are welded to the ends to form the returns either side. I may bolt these to the front of the wings or just use some sort of flexible fixing.

The aluminium plates and tube fix to the front of the steel providing a bit of a crushable area and a fixing point for the bumper skin/spoiler.

To make the frame I start with the centre bend. I mark a tapered cut on the tube with fine marker pen and cut with a hacksaw three sides of the tube. I offer up the tube and g-cramp it to the bumper fixing brackets. This forces it to the correct angle. I then use a piece of flat bar and two more G-clamps to hold it a the correct angle take it from the car and run bead down the joins with a MIG welder. I then clamp the other tube to the original to ensure it is at the correct angle before welding that. I carry on in this manner for the two welds either side of centre on each of the two tubes.

Using pieces of wood and G-clamps to hold the two tubes the correct distance apart, I then G-clamp the two plates that will bolt the frame onto the car to the tubes, take it away and weld on the plates. (The correct distance apart is a distance that allows enough space for the indicators/side lights to sit in between but is not so wide that the bumper will not fit on. With 25mm tube it just about works!)

The end plates are notched to fit between the tubes. A little tiny tack, back on the car, bend it to the correct angle, back to the bench and weld it up.

It’s going to look a bit like this when it’s finished.

Next, making the “temporary” GRP cover  for the bumper frame.