I'm building a cad model of a UTLX type V tank car per the drawings found on
page 344 of the 1906 CBD. I have a question about the term "Dish" as it
relates to the tank head. I hope some of you guys can help define **an
aspect of the term** that I don't understand.



It is apparent to me that "dish" refers to some how far the metal has been
pressed so as to form the tank head - afterall, looking at the pressed steel
from the inside of the tankcar, it would look like a dish. My question is,
when the drawing says a 6" dish, that dimension is between two points. One
is obviously in reference to the furthest point out that the steel has been
pressed - but 6" from what relative to the anything else? And is that 6"
dish measured to the inside or outside of the head?



Looking at photos, what I see is the car end is a solid sheet of steel,
after being pressed into a dish, retains some distance of metal that slides
tightly into the tank, for use in riveting end to tank. That is to say,
extending beyond the dish itself is a steel cylinder, marginally more narrow
than the tank itself. A small portion of this inserted cylinder remains
exposed, just outside the end of the tank. This cylinder begins to curve
inwards, oh, on perhaps a 1 inch radius and then takes on the outlines of
the dish.



So. is the 6" dish relative to the end of the car, the end of the cylinder
where that 1" radius curve begins, or right where the dish form begins?



Yeah, I know. some of you HO scale guys are going "you gotta be kidding me,
right?". Nope. It's getting the model done correctly.



Can anyone help me out here? Ummm, I think I should also ask, anyone know
of where I might find a more complete drawing(s) for anything of this car?
I'm also wanting to do the X-3 design after this one.



Thanks in advance!



Dave Nelson

Dave

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.

The lagging is to be 4" between the exterior of the tank and the
interior of the jacket. The jacket is specified as 1/8" thick.

Tom





I'm building a cad model of a UTLX type V tank car per the drawings
found on
page 344 of the 1906 CBD. I have a question about the term "Dish" as it
relates to the tank head. I hope some of you guys can help define **an
aspect of the term** that I don't understand.

It is apparent to me that "dish" refers to some how far the metal has
been
pressed so as to form the tank head - afterall, looking at the pressed
steel
from the inside of the tankcar, it would look like a dish. My question
is,
when the drawing says a 6" dish, that dimension is between two points.
One
is obviously in reference to the furthest point out that the steel has
been
pressed - but 6" from what relative to the anything else? And is that 6"
dish measured to the inside or outside of the head?

Looking at photos, what I see is the car end is a solid sheet of steel,
after being pressed into a dish, retains some distance of metal that
slides
tightly into the tank, for use in riveting end to tank. That is to say,
extending beyond the dish itself is a steel cylinder, marginally more
narrow
than the tank itself. A small portion of this inserted cylinder remains
exposed, just outside the end of the tank. This cylinder begins to curve
inwards, oh, on perhaps a 1 inch radius and then takes on the outlines
of
the dish.

So. is the 6" dish relative to the end of the car, the end of the
cylinder
where that 1" radius curve begins, or right where the dish form begins?

Yeah, I know. some of you HO scale guys are going "you gotta be kidding
me,
right?". Nope. It's getting the model done correctly.

Can anyone help me out here? Ummm, I think I should also ask, anyone
know
of where I might find a more complete drawing(s) for anything of this
car?
I'm also wanting to do the X-3 design after this one.

Thanks in advance!

Dave Nelson

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

While I can't speak for a hundred years ago, here's how it works now and would have already been by the fifties, probably earlier.

The 'other' point, actually a line, you are looking for is the tangent. That's where the different curves of a head meet the cylinder (shell). There are plenty of head manufacturers around now, so it's easily Googled. The term 'dished' really means that the head, proper, has a curve to it, as opposed to a flat head with a transition curve to the tangent like some of those marine boilers that were written about in this group a year or two ago.

There are many common contours, and many common radii to the dish part, with common ones being around the same as the diameter or the shell up to 2x the diameter of the shell. As this number gets larger, the head gets flatter. Then one has to know the knuckle radius. The knuckle is the transition curve from the dish radius to the straight flange (flat cylindrical surface beyond the tangent point), which is where the attachment to the shell takes place. Now, with butt welding, the straight flange only needs to be about 2" or so long but with riveting it was undoubtedly longer.

Your 6" dimension actually describes the curve pretty well -- you just have to estimate the knuckle radius and do a little curve fitting. Obviously, the larger the tank shell diameter the flatter the head will be if the height is constant. Note that, if the head is 1/2" to 1" in thickness, it makes relatively little difference whether this is measured to outside or inside but tank guys now usually care only about the ID.

Ron Merrick

Rod, sounds like you know this stuff already but it's new to me. Let me
paraphrase, using your terms, what I'm understanding here... tell me if I
got it right:

WRT the first point on the 6" distance. Most likely this is a point on the
inside of the head where it has been pressed furthest (most probably the
centerline of the tank cylinder) . The second point, following that
centerline, lies on a point on the circular plane parallel to the end of
cylinder of the tank / perpendicular to its sides...

a) where the dish ends and the knuckle radius begins, or, moving a bit
closer to the tank itself...
b) where the knuckle radius ends and the straight flange begins, or moving
right to...
c) where the original end of the tank cylinder is found.

On reading your comments I thought the point in question could be (b) but
is most likely (a) where the dish begins to turn into the knuckle radius,
if, for no other reason, your use of the word knuckle was describing a
different thing than what you described when you used the word dish. (c)
doesn't make as much sense to use in context of the actual operation to
press the dish itself so it is rejected.

Is my conclusion -- most likely (a) -- your best understanding as well?

Dave Nelson

p.s. I did use google before my first post... too many product offerings, no
explanations I could follow, plus being attacked by one of those phony
you've-got-a-virus scams. Good 'ol STMFC!

--- In STMFC@..., "Dave Nelson" <Lake_Muskoka@...> wrote:

a) where the dish ends and the knuckle radius begins,

Ron hasn't replied, but what I take away from his message is that, while the head is one piece of steel, it has three distinct features:

The flange. The bend that turns the flange ninety degrees from the axis of the plate, called the knuckle. The dish that pushes the center of the plate out and gives it more resistance to bending under load. Each of the three would have been dimensioned separately, although maybe not on a general arrangement drawing such as what you are looking at, so the dish dimension refers only to the area past the knuckle bends.

Dennis

Dave:

Yes, the first point is dead center of the head, normally the inside. The second point, the tangent line, is the opposite end of the knuckle radius so is actually your point (c).

Tank lengths (not necessarily true of tank cars of this ers) are often stated as "t-t" or tangent to tangent lengths, with some kind of head that the user is familiar with. I noticed another response concerning an ellipsoidal tank head, and the specific case described where the "minor axis being one-half the major axis" is today called a 2:1 semi-elliptical tank head, because there is often still a knuckle radius with smaller curvature.

Try www.bakertankhead.com/products/tank-heads.htm for a more technical description of heads.

This particular site shows the straight flange part of the head as "s.f.". I think on riveted tank cars, the tangent point can be taken as essentially the end of the cylindrical portion of the shell.

Hope this helps.

Ron Merrick


--- In STMFC@..., "Dave Nelson" <Lake_Muskoka@...> wrote:

Rod, sounds like you know this stuff already but it's new to me. Let me
paraphrase, using your terms, what I'm understanding here... tell me if I
got it right:

WRT the first point on the 6" distance. Most likely this is a point on the
inside of the head where it has been pressed furthest (most probably the
centerline of the tank cylinder) . The second point, following that
centerline, lies on a point on the circular plane parallel to the end of
cylinder of the tank / perpendicular to its sides...

a) where the dish ends and the knuckle radius begins, or, moving a bit
closer to the tank itself...
b) where the knuckle radius ends and the straight flange begins, or moving
right to...
c) where the original end of the tank cylinder is found.

On reading your comments I thought the point in question could be (b) but
is most likely (a) where the dish begins to turn into the knuckle radius,
if, for no other reason, your use of the word knuckle was describing a
different thing than what you described when you used the word dish. (c)
doesn't make as much sense to use in context of the actual operation to
press the dish itself so it is rejected.

Is my conclusion -- most likely (a) -- your best understanding as well?

Dave Nelson

<snip>> -----Original Message-----

From: STMFC@... [mailto:STMFC@...] On Behalf Of
mopacfirst
Sent: Sunday, February 06, 2011 2:35 PM
To: STMFC@...
Subject: [STMFC] Re: Dished Tank Head

While I can't speak for a hundred years ago, here's how it works now and
would have already been by the fifties, probably earlier.

The 'other' point, actually a line, you are looking for is the tangent.
That's where the different curves of a head meet the cylinder (shell).
There are plenty of head manufacturers around now, so it's easily Googled.
The term 'dished' really means that the head, proper, has a curve to it, as
opposed to a flat head with a transition curve to the tangent like some of
those marine boilers that were written about in this group a year or two
ago.

There are many common contours, and many common radii to the dish part, with
common ones being around the same as the diameter or the shell up to 2x the
diameter of the shell. As this number gets larger, the head gets flatter.
Then one has to know the knuckle radius. The knuckle is the transition
curve from the dish radius to the straight flange (flat cylindrical surface
beyond the tangent point), which is where the attachment to the shell takes
place. Now, with butt welding, the straight flange only needs to be about
2" or so long but with riveting it was undoubtedly longer.

Your 6" dimension actually describes the curve pretty well -- you just have
to estimate the knuckle radius and do a little curve fitting. Obviously,
the larger the tank shell diameter the flatter the head will be if the
height is constant. Note that, if the head is 1/2" to 1" in thickness, it
makes relatively little difference whether this is measured to outside or
inside but tank guys now usually care only about the ID.

Ron Merrick