Is this unusual?

[alwion]

Never had seen a knob like this on the bottom of a read shell, is this unusual? ebay # is 171166530448 if you need to see the style of shell

[John D. Bartleson Jr.]

sir,
  The hole is aparently the inerting access.  The raised lip in question could have bee caused by the drilling operation. Otherwise I have no idea of its purpose. Could it have been cast as a thicker part of the shell base so the lathe dimple would not be near the explosive cavity?
Regards,
John

[CarlS]

Yes, I've seen a couple like this and it appeared to me to be the remains of the casting sprue from forming the shell body.  They are oddly very pronounced.

[Pete George]

That peculiarity is commonly seen on the "base-knob" of what I've called the Virginia Prototype version of 3" Read Bourreleted shells. It is simply a projection caused by slightly overfilling the ironcasting mold's pressure-release vent.

For anybody who doesn't already know what the mold's pressure-release vent is:
  When you pour molten metal into a casting mold's cavity, there MUST be two holes in that mold.  One is the filling-hole.  The other hole is called the vent-hole. The molten metal entering the mold's vcavity very rapidly superheats the air inside the cavity, causing that air to rapidly expand. If the expanding air's only avenue of escape is through the filling-hole's long vertical tunnel, the guy doing the pouring will get molten metal blown in his face. The vent-hole allows the expanding air to escape by another route.  The vent-hole is almost always circular. Of course, it is always located at the very top of the mold during the metalcasting process.

  As I indicated above, ALL metalcasting molds (except very small ones, like a bulletmold) have a vent-hole.  Therefore, various civil war artillery projectiles sometimes show the remnant of an "overfilled" vent-hole.  The projecting metal is usually chiseled off more-or-less flush with the projectile's surface.  The vent-hole mark is occasionally seen on cannonballs, directly opposite from the fuzehole.  Most US-made Read-Parrott shells also show it, in the center of their base. Most Schenkl projectiles also show a "vent-hole remnant" on the bottom of their tail-knob.

Regards,
Pete

[alwion]

Thanks guys, I had considered a casting sprue, but this brings another question. If this was the vent /overflow, what would be the location of the fill sprue? If using a sand mold and a fill channel, was it on the side and ground away?I have a vague idea of casting process, and you know the molten metal would have to level in the two sprues.

[Pete George]

Alwion wrote:
> If this was the vent /overflow, what would be the location of the fill sprue?

  The metalcasting mold's filling hole is always located at a seam between the mold's parts. See the diagram below.

  On the specific variety of Bourreleted 3" Read shell in the Ebay auction (there are many varieties of 3" Read shell), the filling hole was located on the moldseam at the edge of the "upper" bourrelet.

Alwion also wrote:
> If using a sand mold and a fill channel, was it on the side and ground away?

  The sprue created by the filling-hole channel would be removed by either breaking it off with a hammer or chiseling it off... not removed by a grinder.

Alwion also wrote:
> I have a vague idea of casting process, and you know the molten metal would have to level in the two sprues.

 You can read detailed information about the artillery projectile casting process here:
http://www.pochefamily.org/books/SolidShotEssentialsMod.html

Regards,
Pete

[John D. Bartleson Jr.]

Pete,
   Is there an example of molding for a conical projectile?
Thanks,
John

[Pete George]

Just making sure I'm correctly interpreting your question:
  If your term "example of molding for a conical projectile" means a diagram (like the spherical one I posted), I don't currently have one.  I assisted Dave Poche in constructing "casting diagrams" of three versions of cylindro-conical shells, but I don't know whether has has completed them.  I'll check with him about that, and for permission to post the diagrams if he has completed them.

  Intending to publish the following info in the "Lee's Thunderbolts" book... I've personally observed proof that there are several versions of casting-molds for cylindro-conical shells:
1- What I call a "Bilateral" mold (whose moldseam runs axially along the projectile's length from nose-tip to base, dividing the projectile into two identical halves), mold is oriented vertically with projectile's nose at bottom.
2- Bilateral moldseam, mold is oriented horizontally.
3- Bilateral moldseam, mold is oriented at about a 15-degree angle.
4- What I call a "Stacked" mold (which has one or sometimes TWO seams -- one at the ogive's bottom, and sometimes a second seam at the bottom of the projectile's cylindrical sides), mold is oriented vertically with the projectile's nose at the bottom.
5- A complicated combination of versions 1 and 4, similar to a "3-piece" mold for making glass bottles.

  I've observed Bourreleted Read shells and Mullane/Tennessee-Sabot projectiles which were cast in mold variations/orientations 1, 2, 3, or 4.  Archer projectiles used either version 1 or version 5.  Insofar as I'm currently aware, Schenkl, Dyer, Parrott, Read-Parrott, Read Long-model, and Hotchkiss projectiles were cast only in what I'm calling a version 4 mold. (Note, the numbered list I posted is not arranged in a Chronological numbering system -- it is simply my own compilation of the various civil war artillery projectile casting-mold configurations.)

Edit-note: I used the Modify option on this post only to correct a mis-typing of the word "cylindro-conical."

Regards,
Pete

[John D. Bartleson Jr.]

Pete,
   How did you arrive at the 4 configurations? A Civil War reference on how they were moulded or by sutdying the shells themselves by observing the spru marks?
Thank you,
John

[Pete George]

  I compiled the list of five (not four) casting-mold configurations by combining my observations from studying the shells themselves AND from civil war era artillery projectile casting documents.

Here's some additional information from my personal observatiions:
  As I've indicated in previous posts, the mold's vent-hole HAS TO BE at the mold's very top during the casting process -- or molten iron would pour out.  Therefore, the location of the mold vent's mark on the projectile's body tells us the "orientation" of the mold during casting.
On "Bilateral Mold" projectiles I've examined:
1- I've seen the mold vent mark located between the bourrelets on Read shells, which proves the shell was cast in a perfectly horizontal orientation.
2- I've seen the mold vent mark located on the side of Read shell noses, which proves the shell was cast in a 15-degree leaning orientation.
3- I've seen the mold vent mark located on the bottom of Read shells (and other types), which proves the shell was cast in an upside-down vertical orientation.

  That accounts for three of the casting-mold configurations in my list. The location of mold seam(s) accounts for the other two configurations I listed.

Regards,
Pete

[John D. Bartleson Jr.]

Pete,
I have always thougnt that the "ear" on the ogive of a Read is a spru  and not a
lathe dog ear. I don't believe a lathe dog is used in that manner.
John

[alwion]

Thanks I find this extremely interesting, will watch for additional posts and info. will also see if I can see what shows on my shells, thanks Guys