The black tank you see in the top center of the photo is a water tank, repurposed from an oil tank. With that in place I decided that in addition I needed an oil tank. The problem that jumped out at me was .. as usual .. lack of space. One day after a beer or two I though I could put an oil tank within the bents supporting the water tank. The red arrow shows where I imagined it could go.

It becomes much clearer when shown in Sketchup. Not only can I put a oval shaped tank between the bents (it turned out to be approximately 5,300 gal) .. but there is room also for a pump and motor. How cool is that?

Design

This isn’t anything exact … just some general dimensions .. height, width and length to fit between the bents.

This was in part because I had a length of 1-3/9″ dowel to start with. Never forget the power of the scrap box/stack

Just for fun, let’s calculate the tank volume
The volume of such a tank is calculated by finding the area, A, of the end, which is the shape of a stadium, and multiplying it by the length of the tank, l.A Stadium is a geometric shape with two half-circles separated by a rectangle. The area is calculated by:

The radius,r of the tank is 11/16″ which would be 2.75′ full size.

The diameter,d of the tank is 1-3/8″, which would be 5.5′ full size.

The height,h and length,l of the tank is 3″ which would be 12′ full size.

The side length,a is the height,h – diameter,d which would be 6.5′ full size.

Sticking those numbers into the formula:

With this in hand we can now simply multiply the tank length by this area : V = 59.5\; x\; 12

So ..

Parts

Here we have two lengths of 1-3/8″ dowel a ‘nominal’ 3″ long. I say nominal since the important thing for me was getting the ends square. A disk sander and the protractor set at 90° and that was good to go. A pice of wood to space them apart a bit – I wanted the height to be about 3″ also. Finally two pieces of .040″ styrene for the ends of the tank – cut slightly oversize.

The .040″ tank ends were epoxied to the ends of the dowels. WWhen that had set up I used a sanding block and sanded the styrene down to the dowels. This gave me a core to work with. I experimented with wrapping this core with some cardstock. It worked .. somewhat .. let’s say

Here the cardstock wrapper has been glued to the core. Red Automotive Spot Putty used to fill in low areas. As I said ..it worked somewhat. In the end I found that sanding had cut through to where it was glued to the styrene so I removed the cardstock – need to switch to styrene. That was my first thought but had tried to get around the hassle of bending the styrne with the cardstock .. oh well. Once again into the breech ..

The next step will be to cut a wrapper out of styrene. The Perimeter of a stadium is ..

Inserting the numbers (actual 1:48 scale sizes) into the formula ..