Rear firewall (again).

October 22nd, 2013

Today I started working out the new rear firewall. If you’ve been paying attention you’ll know I have moved it forwards from the original one. This does several things. I get to redo the axle cover I wasn’t happy with, I get to install a larger fuel tank and I get to use the firewall as the back of the passengers seat (the driver will have a bucket).

First I got distracted removing studs from the crankcase. I am sure the gearbox mounting ones are fine but I did want to remove the crankcase to block ones. I found one was loose due to bad threads. I managed to get all the studs out except for three. I removed two by welding a piece of square tube to them to use as a handle. Lots of heat and penetrating fluid then allowed them to be removed. One though sheared off. Luckily I was able to punch then drill it out, finishing off with a suitable tap. All the studs will be replaced with new ones. I also realised the front lip replacement is held with four bolts threaded right though the crankcase. That may be OK to use as is.

IMG_4293_1 IMG_4295_1 Removing crankcase studs.

I then worked on the rear firewall. I used hot glue to stick bamboo skewers to the wooden template. The ends of the skewers touch the inside of the aluminium. The firewall will have a folded flange and I will rivet the aluminium skin to the flange. This should really strengthen the body.

IMG_4297_1 Skewers.

The clamps are holding the skin down in the position it will be once the edges are wrapped around the frame.

I then removed the template from the frame which first meant removing the skin. That is now standing on end in the garage. Since it was off I took the opportunity to weld up a small split in the folded over front edge of the skin.

With the template out of the car I laid it out on cardboard to mark around. I will make a cardboard template the exact shape then use that to cut out the steel. I marked the ends of the skewers on the cardboard then used the flexi-curve to join them with a smooth curve. I had trimmed two of the skewers on each side (where the side tube is) but I was careful to cut an exact amount off them so when I marked things out I just added the same amount back on.

IMG_4301_1 IMG_4302_1 Marking out firewall.

Once I had it marked out I started cutting it out. It occurred to me as I got to half way that if the body is symmetrical I should be able to fold the template in half and the two sides should be the same. I folded over the piece I had just cut out and the two sides are very close. There is maybe 1/8th of an inch difference.  Pretty good for a hand made car! I don’t think my MGB is that accurate actually.

IMG_4303_1 IMG_4305_1 Almost symmetrical.

I left the cardboard template under some sheets of steel to get it sitting flat. I might need to glue some reinforcing to it so it stays flat but then I can test fit it in the car. If it matches the inside of the skin I can then trace it out onto a piece of panel steel and then cut it out, remembering of course the flanges all around the edges.

IMG_4307_1 Skin off.

Oh, my rustic steering wheel covering totally failed. When I looked at it today it was all loose and the string easily moved about on the rim. So I took it all off again!

2 Responses to “Rear firewall (again).”

  1. Nigel Hamlin Wright Says:

    Cod line’s the thing for the steering wheel Simon, my binding (about 15 metres) hasn’t budged in 3000 miles.
    Great work and I’ve taken note of the thing with the sticks – great idea.

  2. admin Says:

    I think you’ve told me that before but I seem to remember not having much luck finding it here!

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