Bonnet hinge.

March 24th, 2015

After finishing that last update I felt guilty I hadn’t done anything on the car so actually went out and did something! First I fixed the ends of the bonnet hinge channel piece so the closed is is closest to the driver not the front of the car. I also played about with making a little jig for folding up the intricate little bonnet main hinge pieces.

The jig is just two bits of 6mm steel plate joined together with a section of square hollow tube about half an inch square. A piece of threaded rod with a nut on each end holds it all together but also allows some adjustment. Holes are drilled in the end plates through which a piece of brass rod, the same as being used for the hinge pin, can fit. The rod has to be accurately positioned in relation to the square tube to form the correct hinge piece shape. I originally drilled the holes in the wrong place hence the unused ones.

I start with a flat rectangle of a fixed size and bend a 90 degree fold on it in the vice.

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I then make another fold on the short side around another piece of the same square tube as in the jig.  I have two little sort sections of this I use at various times in this process.

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This fold is also done in the vice which is handy for tightening them up around the tube. This is then slid into the jig and the jig clamped in the vice. I then pull the long side around the brass rod. I tap it down using a piece of hardwood and a hammer.

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Then the jig is removed, turned around, and put back in the vice so the metal can be bent the rest of the way around.

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Next the jig is rotated again and the little end piece hammered around. Again I can make use of the vice to tighten the folds by moving and turning the jig.

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The jig is then removed from the vice and the brass pin pulled out to reveal a partially formed hinge piece. I tighten it up a bit in the vice with my short square tubes if need be.

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Next I take a critical little piece of metal. This is 2mm thick and half an inch wide and it is this that forms the critical part of the folds. It forms the slot the aluminium of the bonnet pieces will slide into. I use a small piece of angle iron and use that to clamp the hinge piece in the vice holding the flat piece in position. Then I fold over the two layers of metal. Again the hard wood block and a hammer helps here to fold it most of the way around. I replace the brass pin at this point to avoid crushing the tube part.

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Next I simply finish the fold by crushing it in the vice. You can then remove the piece, knock out the little spacer and you should have a formed hinge piece.

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The hinges are all pretty much the same size but not identical. The amount of overlap I have on the end after the last fold seems to vary. But I think  as long as the actual gap from the hinge to the end of the fold is the same on all of them it won’t matter. And the differences in overlap won’t be seen because the bonnet covers that part. You can see how that works with the little scrap test piece I have below.

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I need to check with Joss if these are going to work OK. Each one takes about 10 minutes to make and I made a few just to get the hang of the process. I’ll need about 12 of them for the whole hinge on the car. I made three tonight and had a few other prototype ones that might be useable as well.

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2 Responses to “Bonnet hinge.”

  1. Nick Boorman Says:

    I’m currently rebuilding a type 65 Austin 7 and have struggled to find a top hinge for the bonnet. So really good to see your article. Nice piece of work.

  2. admin Says:

    Hi Nick, we should be starting on the rest of the bonnet this weekend hopefully.

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