Silent Saloon.

[Mike Costigan]

Sounds about right, 4.3 litres is just short of one gallon.

[Malcolm Parker]

Duncan, I think your card mock up is possibly on the big side!  If you refer to the original photo and compare the base of the tank against the radius of the wheel, to my mind the tank is slightly smaller, so with a 19" wheel I think the base of the tank can't have been more than about 9".
Just a thought!
Sorry I'm still in inches.

[Ruairidh Dunford]

Funnily enough, I have just suggested the exact same measurement to Duncan.

[Ivor Hawkins]

Ah, but Duncan’s filler is at the correct angle!

[Duncan Grimmond]

Thanks to all. Got to maintain an upright position as well as a stiff upper lip regardless of inclination(intoxication?).
I'd say it's near the size of the wheel centre which is around 9" rather than the 12" I guessed. At that size the capacity drops to around 2.4 litres, damn that pi ratio!
Still could get you home in extremis though...

[Bryan Downes]

Duncan,

You may have already done this, but , using photo shop to produce a layered rectangle to sit exactly over the space between two spokes,and then move and rotate the rectangle to align with the bottom edge of the tank and scaling it, the bottom edge of the tank come out at 7.5 inches if I did my sums correctly? It is then possible, I think to scale the rest of it. Anyway, you get my drift.

All the very best with this project.

Bryan

[Duncan Grimmond]

I'm afraid that's a bit too boffinaceous for my meagre computer skills. I held a transparent scale ruler up to the screen and magnified till it hit a round number...

[Alan]

Years ago I had a large and ancient Alvis. It had a reserve tank. So, when driving home from a party in the early hours and the engine started to misfire a quick flick of a switch in the cockpit restored fuel supply. There were two gallons in reserve. Thirty miles later another quick flick revealed that the switch had already been flicked. I imagine wing tanks have similar properties.

[JonE]

what is the view on the Swiss car's tank? Is it a higher capacity version and original, or has it been fashioned in the period when it was all painted red?

[Malcolm Parker]

I've just been looking at the Wyatt book Austin 7 Pictorial Tribute and on page 38 there is a period photo of a Sunshine Saloon fitted with a half round wing tank.   My attempt to scan the page failed miserably!