Pat Wider posted a builders photo of UTLX 39150 in December. Now
I've looked at this thing more closely, versus all the ACF shots in
the Kaminski tank car book, and one more thing that I see is that the
knuckle radius on the heads is much larger on this car than on most
of the other welded tanks built during the late 40s - early 50s when
the welded tanks were first built. (Knuckle radius is a pressure
equipment term, the "knuckle" on a tank head being that part between
the tangent and the main semi-spherical portion of the head, you
might say the "corner".) The dome head on the other hand has a very
tight knuckle radius.
Question is, first, am I seeing this right? The apparent contour of
the tank handrail seems to bear it out. Second, is it a fair
conclusion that most of the early welded tanks had a really tight
knuckle radius like most riveted tanks did, and this is an anomaly or
an experiment? The heads on this car look to me like normal
ellipsoidal heads, which I should be able to get from Plastruct or
similar. By the way, the Red Caboose model has the really tight
radius heads and dome head.
It looks like by the mid-fifties, when the Kaminski tank car book
ends, the ellipsoidal head had become the normal choice. This makes
sense since the larger radii are better for resisting pressure and it
may be easier to press a head with the larger radius.