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153. Tanking it

27/02/2015

I visited Ian Harris yesterday where he and Rick were hard at work on the petrol tank.

One of the oddest features of the design is the back edge of the top cover. The picture below shows it more or less straightened out and you can see two things.

First, because the tank is more or less semicircular in cross section, and the back is sloping to match the slope of the cabane struts, the back edge is curved.

Second, the edge has been doubled over onto itself.

The top of the petrol tank before being fixed to the rest of the tank. This is the back edge which has been doubled over. It was easier than we thought to do, but we still don't know why it's there!

The top of the petrol tank before being fixed to the rest of the tank. This is the back edge which has been doubled over. It was easier than we thought to do, but we still don’t know why it’s there!

We don’t know why it’s been doubled over like that, but we’d spent weeks worrying about how to make that doubled-over edge, and considered abandoning it altogether, making the flange of the rear end stick outwards instead of inwards, and making it out of a separate curved strip of steel that would be soldered to the top cover.

In the end, Ian decided to do what it said on the instructions, and folded it over our wooden former to get the initial fold in the right place, then continued tapping it all the way over, and finally running it through the rolls to even it up. The result is absolutely perfect, and only took about half an hour, apparently! It’s also much easier to form around the back end than we feared.

So now we just need to find out what it’s for…

By the end of the day, the tank was as you can see. The sump and mounting channels are permanently riveted and soldered to the bottom, and the top and bottom are permanently riveted to the back.

Petrol Tank from rear

Petrol Tank from rear

Petrol Tank from side

Petrol Tank from side

 

Petrol tank from front

Petrol tank from front

Petrol Tank rear riveted seam. The rivets are 1/2" apart, and the seam took an entire afternoon to do.

Petrol Tank rear riveted seam. The rivets are 1/2″ apart, and the seam took an entire afternoon to do.

So what’s left to do – in order – is:

Rivet the rear baffle plate to the top and bottom.

Rivet the front baffle plate to the top and bottom.

Rivet the front plate to top and bottom .

Solder the filler neck in place (it’s just loose at the moment).

Easy. Except that each rivet has to be fiddled into place from the inside using a pair of tiny pliers. Then you hold it in place using a magnet while you move the tank over a specially-built anvil, consisting of a long piece of steel bar, about 30mm x 75mm, clamped to a very solid post on the floor and a machine tool, to leave sufficient overhang to reach the full length of the tank. On the end of it is mounted a ‘set’ – a tool like a punch with a hollow nose which the head of the rivet sits in. Once you’ve got that all in place without dropping the rivet, pop a copper washer over it and rivet it in place using a hammer and a LOT of skill, as one false move will send the rivet crooked and it will have to be very carefully drilled out before starting again.

It probably only takes about three good taps using another set on the top to complete the process.

Now take a look at the number of rivets in each seam, and you begin to get an idea of the time and effort involved in making the b***dy thing.

But it, along with the propeller, will be the piece de resistance of the build, and we think that we’re looking at another two or three days to completion.

Can’t wait!

 

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