On Feb 6, 2011, at 1:07 PM, Tom Birkett wrote:

Remember that as you are looking at a photo of a Class V car that you
are looking at the jacket head and not the tank head. The shape of the
tank head is "semi-ellipsoidal" in general but the 1930 American
Railroad Association "Specification for Tank Cars" under "ICC-105A300"
states that "the tank head shall be an ellipsoid of revolution in
which
the major axis shall equal the diameter of the shell and the minor
axis
shall be on-half of this." I think this is enough information to
answer
your question. I'd have to pull out some old math books in order to
write the equation for the tank head.

Tom, You've inadvertently provided a helpful answer to a completely
different question. You are referring to the AAR class V, for
insulated high-pressure tanks. Dave was asking about Union Tank
Line's class V cars, their designation for the early 20th century Van
Dyke frameless cars.

Richard Hendrickson