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Hold height constant. Then a Rectangular Prism, with length and width = radius of the cylinder, has greater volume! So why aren't tank wagons (railroad vehicles that transport gas and liquid) Rectangular Prisms?

enter image description here

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    $\begingroup$ But how well does that shape support loads like pressure and bending? $\endgroup$ – Solar Mike May 15 '20 at 20:39
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  • A cylindrical structure will have a lower surface-area to volume ratio than any other shape that will fit in the structure gauge of railway infrastructure.
  • I can't be certain but that tank looks as though it has been formed by continuously rolling a continuous helical coil from a flat strip. This lends itself to a continuous process of coiling, welding (with the seam passing by the fixed welder) and then chopping the "pipe" into wagon sized lengths.
  • The cylinder will be very strong. It appears from the photo that the tank is self-supporting. No need for chassis so there is further weight saving.
  • Possibly the weight of the full tank results in close to the maximum axle loading. A bigger tank couldn't be filled (although a shorter wagon could be built).
  • The cylindrical shape eliminates all corner stress points and seams except for the end caps.
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  • $\begingroup$ I left my comment so the OP could learn for themselves by doing a bit of research - instead of handing out to them on a plate... $\endgroup$ – Solar Mike May 15 '20 at 21:04
  • $\begingroup$ OK, Mike. I didn't read it as a homework question and if I had I would have prompted the OP through the thought process. $\endgroup$ – Transistor May 15 '20 at 21:11
  • $\begingroup$ This isn't homework. Thanks for your assistance. $\endgroup$ – NNOX Apps May 15 '20 at 21:25

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