Bonnet bulge for MG Midget, to clear turbo charger.

A customer came to me recently with the request to solve a problem with his MG Midget turbo conversion. He had rebuilt the car himself and as part of that, installed a MG Metro turbo charger. The trouble with this is that parts of the installation stand proud of the bonnet. He had already cut a hole in the bonnet around the protrusions, and my brief was to make a bulge to cover this.

One problem with the MG Midget bonnet is that it is very flexible, and when lifted up and down, it twists considerably. This can lead to cracking around the edges of bulges which are not extremely well mechanically fixed to the car. Rivets covered with filler will not do.

In this instance, it was decided to make a bulge in steel, and seam weld it in position. This is a tricky operation as heat build up and transference into the bonnet skin can lead to severe distortion and warping of the skin, so extreme caution has to be taken to avoid this. I believe however, that this is the only way to avoid the otherwise inevitable movement in a screwed and glued joint, under flexing when the bonnet is in use.

The bonnet, plus hole, in place on the car. A strip of 1 1/8" high aluminium strip is shown behind the hole for some idea of scale.

The Solution

Starting with a flat sheet of mild steel.....

....a few hours with Radio 4 and the English Wheel produced this little beauty.

Trimming to fit.

And finally seam welded into place.

Flaring in position with marine epoxy all round will further serve to distribute the flexing loads and the below is the finished result.