Why are tanker trucks always cylindrical and not cubes?

Question

Tanker trucks (which carry liquid) are always cylindrical. Their cross section is a circle as opposed to normal trucks which have a rectangular cross-section. There must be a real-good reason for this. However, i cannot figure it out.

Answer 1

There is ... A circular structure is stronger than the rectangular design. The stresses are distributed evenly around the body. The rectangle has corners which are high stress areas and are more prone to manufacturing defects and failures.

Answer 2

hmm, keen observation there! There is one theory that for the same amount of surface area (read tanker wall material), a cylinder will carry more volume than a cuboid/parallelopiped (rectangular block). That is also the reason why bubbles, drops etc etc have spherical shape.
But if we don't care about that, maybe the mechanics of truck motion come into play! the liquid tends to splosh about a lot less in a cylindrical tank, because of the curved sides which will channel the liquid downward. On the other hand, a rectangular container will spill, splash all the way!
As regards to cement trucks, the tank needs to be rotated about its axis so a circular profile is better.

Answer 3

In a word: pressure.

Cylinders distribute the pressure of a liquid or gas evenly throughout the tank, a square tank has significant weak points at the corners.

In fact, tanker trucks aren't always cylinders, occasionally you'll see a couple of spherical tanks on the back of a trailer. Cylinders are round and distribute the pressure well, but their ends are still not ideal. A sphere is the best shape, but they aren't really easy to use, so most of the time you'll see cylindrical tanks.

Answer 4

Look at the area to circumference ratio of different geometric shapes. The circle gives the largest area per unit of circumfernce. It follows that the construction of a cylindrical tank will use less material than a rectangular one of equal volume.

Answer 5

It keeps the motion of the liquid within stable under conditions that the road way might throw at the driver and vehicle.If the liquid is not able to splash forwards and backwards it could make the truck turn over.

Answer 6

To limit the ammount of movement during transportation.

The motion of liquid in a cylindrical shape is generally towards the middle, and in a square or rectangle is towards the outer edges.

Answer 7

More volume per amount of material (steel, aluminum etc). Also stronger for amount of material as any vessel put under pressure (of even construction) will try to form a circle.

Ideally the tank would be a sphere but this would be impractical to take on the roads and harder to manufacture

Answer 8

A cylinder will have equal capacity to resist pressure than any other shape, except, maybe, a sphere.
A cube will have different properties at the corners than at the centers of the walls.

Answer 9

The cylindrical shape has less joints, and is far stronger than a cubic shape. Why, I ask YOU, is a Gas Cylinder the shape it is... a question of strength. Again, Ostrich eggs...you can WALK on them.

Answer 10

Main thing is surface area to volume ratio is less as compared to square tanks, so it will contain more volume as compared to the same s.a. of square tank.

Another thing is that it is having two circumferential and one longitudinal welding joints.while square tanks have atleast 12 weld joints which make it vulnerable to failure and less stronger than cylindrical tanks.(not considered the top nozzles.)
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Angle of friction is continuous and hence friction will be during transportation which makes it safer especially in case of imflammable chemicals/hazardous chemicals.Square tanks are having sharp edges which causes friction.