Question about Copper or Brass Plate below Main Fuse on 12 pdr

[callicles]

This is a case-shot my brother found and had sectioned.  He took pictures, well enough, I think, that the copper or brass plate is visible to those who look.  It is in between the main fuse and under plug.  It seems to mimick a washer. Could someone explain what the purpose of this was?  I knew that there might have been a washer-type item, but I did not know that it had a factory hole in it.

My point is this:  I thought the washer or plate was there to keep moisture out. This appears to have a factory hole in it.

Thanks

[Pete George]

  I would guess that you (like me) have never seen a civil war era document which tells the "proper" name for the thin sheetmetal "moisture seal" disc on the underside of Bormann fuzes. Pardon me please, but I have to say it is much too thin to be called a "plate."

  Based on my longtime extra-close observations of the differences between US and CS-made Bormann fuzes, in US ones the moisture-seal disc is sheet-iron, and CS ones it is sheet-copper.

 You are correct about the sheetmetal disc's purpose.  It covered an aspirin-shaped tablet of mealed blackpowder in the circular cavity in the center of the fuze's underside.  The sheetmetal moisture-seal disc was intended to be "pierced" just prior to installation in the shell.  Based on what I've seen, the number and form of piercings varies.  Some piercings look like they were made by a tiny sharp nail or tack-point, and others look like they were made by a very sharp-pointed narrow knifeblade.  In most cases I've seen, there were three or four piercings.  On others, there was only a single piercing, which was circular, as if the point of narrow-tip knife was inserted and twirled.

  Please note, I've specified that the above infomation is based on what I've seen.  If other readers here are in possession of civil war documentation which contradicts anything I've said, I'd genuinely like to hear it.

Regards,
Pete

PS -- I've modified this post to correct some embarrassing typing errors, such as mis-typing the name Bormann in the first paragraph.

[John D. Bartleson Jr.]

Pete,
  According Gibbons, page 258, Bormann Fuse, the magazine of fine powder is covered with a thin piece of tin and soldered into position.
    As I interpret the discription, the holes are punched to insure that the piece of tin is blown out to ignite the shell.
     I wonder if this piece of tin might be sometimes blown into the hole in the support plug causing a dud.
     This is Gibbon's discription, I don't know how many companies made this fuse or if it was made by one copany, however the tin disk could have been replaced.
John

[CarlS]

Very interesting.  I find it surprising they would use sheet iron to cover it and punch a hole in something that could chance a spark.  I had just always assumed the unpunch Bormann fuse acted as the moisture seal.   I don't recall ever having seen a tin or copper disk on top of the underplus like that nor any traces of solder on an underplug or surrounding iron.  With as many Bormanns as were fired you would think there would be a special tool for punching those.  Does anyone have an image of one with no fuse but the seal in place?

[emike123]

I am having a hard time following this without pictures.

Here is a shot of the underside of a US Bormann fuse.  I think the seal they are talking about is not a separate piece, but in the bottom of the fuse in the area I've circled

[Pete George]

  Note: Emike's post was made during the 90 minutes it took me to research and type this post.

  The thin sheetmetal disc is part of the Bormann fuze itself -- it is not "put onto" the top of the fuze's underplug.

  Perhaps it could be properly described as a Bormann fuze's "base-seal."

  Here is Emike's photo of nine different versions of Bormann fuze.  All the specimens in it are US-made except for the CS-made one in the center of the photo. One at the center-right is missing its base-seal disc.  You will notice that some of the sheetmetal "base-seal" discs have only a single pierced hole (which is sometimes off-center), and others have several holes.  The thin sheetmetal disc seems to have been machine-pressed into place.

  Please note that the photo mostly shows rusty discs.  Therefore, they are NOT made of tin.  They are just tin-plated iron sheetmetal ...like a "tin can."  The term "tin" is used overly broadly even in civil war era writing.  For example, there were no "tin" canteens.  Actual tin is a very brittle metal ...and it deteriorates badly in below-freezing temperatures.  I've read that Napoleon's troops had actual tin uniform buttons -- which literally fell apart during the frozen retreat from Moscow.

  Pardon me, please, for straying from the main subject in order to dismantle the misleading "tin" description by Gibbon.  I hope this post provides clarification about the Bormann fuze's thin sheetmetal "base-seal" disc.

  As I said in a previous post, all of the ones I've personally examined which were copper sheetmetal were in CS-made Bormann fuzes.

Regards,
Pete

[Pete George]

John D. Bartleson Jr. wrote:
> Pete, According [to] Gibbons, page 258, Bormann Fuse, the magazine of fine powder
> is covered with a thin piece of tin and soldered into position.

  I have to wonder how it was possible to solder the "base-seal" disc into place over the powder without ignitiing the powder.

> As I interpret the discription, the holes are punched to insure that the piece of tin is
> blown out to ignite the shell.

  The purpose of the punched hole(s) cannot be "to insure that the piece of tin is blown out to ignite the shell" ...because there is no space for the "piece of tin" (the sheetmetal disc) to be blown into except into the underplug's flame-hole.  (Which would clog it, as you suspected.)  The purpose of the pierced/punched holes in the "base-seal" disc is to allow flame from the fuze to enter the flame-hole in the underplug.

Regards,
Pete

[CarlS]

Makes perfect sense now!  I've never found a Bormann fuse in good enough shape nor purchased one with that disk/wafer there thus not noticed it.

I just looked at Chuck Jones' book and you can clearly see the small metal wafers in the bottom of most of the Federal examples he shows.  As Pete says, they have different hole counts.  The CS example does not have the wafer.  Not to distract from his most excellent work, I must also add that I feel it an oversight that he didn't discuss this.  The closest he gets to it is: "The flame then passes through a channel to the fuse's small center powder magazine which explodes sending flame through the flash hole of the under plug and into the shells bursting charge."  There is no mention of any moisture barrier covering the "powder magazine" nor the need to punch holes in the bottom of the fuse.

Perhaps the holes were punched before applying the wafer to the fuse at the factory.  The powder magazine, as Chuck Jones calls it, is packed with powder and you would want something over it to keep the powder in place during handling.  So it makes perfect sense to pack the magazine with powder and then cover it with a holed wafer which would hold the powder in there yet allow the flames to pass though and explode the shell.

[CarlS]

Regarding the soldering, it looks like from Mike's image that the fuse is filled with powder in the channel and magazine, the wafer put into place and then the back pressed into onto the fuse holding it all in place.

[Pete George]

  Yes... "machine-pressed," like I said in my post.  The horseshoe-shaped piece which closes the bottom of the time index's powder-train was (perhaps simultaneously) also machine-pressed into place.  As with the wafer-ike "base-seal" disc, soldering would be too dangerous, because of the powder inside.

Regards,
Pete

[Pete George]

CWArtillery wrote:
> Perhaps the holes were punched before applying the wafer to the fuse at the factory.
> The powder magazine, as Chuck Jones calls it, is packed with powder and you would
> want something over it to keep the powder in place during handling.

  Yes... it kept the powder in place. 

  I have described the central powder magazine as containing the Bormann fuze's "booster-charge" ...because the ignition of that mass of powder (which is wider than what's in the powder-train) ensures a flame-jet which will go through the small flame-hole (or "tunnel") in the fuze's underplug.  That is similar to a percussion cap's fulminate explosion forcing its way down through the small tunnel in the gun's nipple to the propellant powder.

  Note that the Gibbon document says the Bormann fuze's powder magazine contained fine-grain powder.  Putting a hole (or holes) in the base-seal would let humidity immediately enter and start spoiling the fine-grain powder.  That is why I strongly believe the seal's hole (or holes) didn't get made until very shortly before screwing the Bormann fuze into the shell's fuzehole.

Regards,
Pete

[John D. Bartleson Jr.]

Pete,
  You asked for a civil war reference and I quoted one for you.
Additionally, Gibbons writes that the fuses were checked to ensure the holes were present in the disk, the fuses screwed in place and kept ready for undetermined periods of time and when ready for firing all needed was to punch the time setting desired.
    I don't know how it was soldered in place without the heat causing ignition, I merely quoted a refrence for you.
Perhaps the answer is to refrain from quoting Gibbons.
Cheers,
John

[Pete George]

  Thank you for the reference from Gibbon's Artillerist's Manual.  I took issue with part of what he said, not with you for posting it.

Best regards,
Pete

[CarlS]

Pete,

I thought about that moisture issue too but I keep thinking of how hard it would be to reliably punch holes in that tin covering in the field.  The Bormanns are soft metal and it wouldn't take much to warp them so they couldn't screw into the shell.  I just assumed the fuse was wrapped in a waxed paper or something to keep it dry until used and the punch holes came from the factory.

On the other hand, if the holes were punched in the factory, I would expect them to be machine punched or drilled and not punched with a sharp point as they appear to be.  This would point to the fuses being delivered to the field with the bottom unpunched and then the artillery unit taking a nail or something similar and creating the holes in the wafer.  Then they would screw them into the shells to be ready to use.  This sounds reasonable to me.

Also, see below the bottoms of a couple nice battlefield dug Bormann fuses I have.  On the first one you can see the path from the horseshoe powder train down to the powder magazine.  On the 2nd one, you can clearly see the pressed in piece of white metal to cover the horseshoe shaped powder train.  It also has some odd rings around the powder magazine that don't show on the other one.

[CarlS]

I was looking for something else and coincidentally ran across this humorous snippit from the Richmond Dispatch:

Borman fuse.
 --This new military contrivance, for exploding shells at given times, is now being manufactured in great quantities, at the Virginia Armory, for use in case of emergency. They are made of a substance a trifle harder than lead, and when used are screwed on the shell. The concussion, when powder in the piece is fired, causes the fuse to ignite, which is timed to explode the shell at the proper moment. The Borman fuse is about the size of an old fashioned dollar, is half an inch thick, is numbered from 1 to 5, on the face, and is applied somewhat on the principle of the top of a self-sealing preserve can. We heard an intimation that they were to be tried at the Armory on Saturday.

The Daily Dispatch: March 4, 1861. Richmond Dispatch. 4 pages. by Cowardin & Hammersley. Richmond.