Author Topic: Mysterious Grooves in 150 Pdr. Armstrong Breech (Read 1429 times)

seacoastartillery · « **on:** June 07, 2008, 09:46:03 AM »

While studying the 150 Pdr. Armstrong Rifle at the U.S.M.A at West Point, New York in 2004, Mike and I noticed some mysterious grooves on the underside of the second reinforcing hoop at the tube's breech end. As yet, we have seen nothing in print about the purpose of these grooves. Please look at the pictures below and post a reason for these grooves if you can think of one.

Regards,

Mike and Tracy

The grooves in question.

The drawing shows the dimensions of the Armstrong's grooves and is from one of five complete sets that we recently sent to the U.S.M.A. Museum at West Point, NY. Those laminated photos are of the 7" Brooke that we have been working on lately and are just used here to hold the Armstrong drawing down. I can't see the dimensions on the drawing so here they are: Grooves 26X each side, .125" w, d, sep., 5.00" long.

Mike yuks it up with the U.S. Military Academy's Arms and Armor Curator as Tracy works. We got rained out on this trip and had to continue our measurement of this big gun at Fort Fisher in Kure Beach, NC when it was there on loan. Four days were required to make the field drawing of this beauty. The Excellent Carriage was made by the Paulson Bros.

Any ideas?

cannonmn · « **Reply #1 on:** June 07, 2008, 10:10:16 AM »

Guy in blue shirt must be Les Jensen. Grooves may have been a type of keying to prevent torque generated by firing a rifled projectile from tending to twist the hoops with respect to one another. Usual way would be to put monobloc tapered keys between the major hoops but maybe they felt this was quicker and did same thing without making parts that are a PITA to fit.

seacoastartillery · « **Reply #2 on:** June 07, 2008, 10:32:56 AM »

We had the same thought at first. If this is the case, however, why would they not put these also between the first wrought iron hoop and the cast iron rifled tube? Bye the way we are even now. We like to spell ordnance with and "i" and you just gave Les Jessen an extra "n" and took away a necessary "s".

Regards,

Tracy and Mike

Double D · « **Reply #3 on:** June 07, 2008, 11:25:10 AM »

Breech block got stuck and bubba got out a pipe wrench, a big pipe wrench and broke it loose...best I can come up with.

Cat Whisperer · « **Reply #4 on:** June 07, 2008, 12:24:50 PM »

It was either a presentation model, or a fancy addition for show, OR it was a slick way to cover up a minor 'oops'.

seacoastartillery · « **Reply #5 on:** June 07, 2008, 02:17:02 PM »

Oh Come on!! Both moderators please go back to your cages.

Are there any members out there who are riggers by trade?

Regards,

Mike and Tracy

cannonmn · « **Reply #6 on:** June 07, 2008, 03:45:01 PM »

Quote

you just gave Les Jessen an extra "n" and took away a necessary "s".

Les Jessen?

I'm not claiming to be a great speller but I checked our gun club directory for him and they have "Leslie D. Jensen." The same thing is on the web too.

seacoastartillery · « **Reply #7 on:** June 07, 2008, 03:57:23 PM »

Cannonman, not that is a big issue or anything, but when Mike talked to him on the phone three weeks ago to get a correct shipping address for that big tube of drawings, that's what Less told him. In fact Mike even asked him to repeat the spelling because it sounded strange the first time. Anyway, no big deal and I can confirm that there are at least three internet sites that have it spelled your way.

Now what about the grooves, are you still thinking anti-rotation?

Respectfully,

Tracy and Mike

seacoastartillery · « **Reply #8 on:** June 07, 2008, 06:40:40 PM »

The large lifting gins of the 1850s and 1860s used 5" ropes. The larger garrison gin in particular had big, heavy blocks through which passed these 5" ropes. So as not to confuse anyone, the Armies, North and South specified rope size in those times by it's circumference, not it's diameter which was about 1.6". Unlike the nylon slings which riggers use today, which grip most objects very tightly, the large ropes used 150 years ago occasionally slipped as they had much less surface in contact with the object being lifted. This was especially true on large diameter, smooth objects like cannon barrels. What is the major requirement of the attitude of a cannon's trunnions as the tube is lowered into a new or refurbished carriage? Maybe that the trunnion axis is perpendicular to a radial line going to the center of the earth? That the axis is level?
We believe that the grooves were placed where they are to prevent hoisting rope slippage during a garrison gin lift or a dockside crane lift from or to the deck of a ship. so, what do YOU think? Are we daffy or correct here? Hopefully the lift of a 9" Dahlgren at the National Civil War Naval Museum at Port Columbus, Georgia will give you an idea. Hope this link works; it's a very brief video clip.

Regards,

Mike and Tracy

[img width= height=]http://img532.imageshack.us/img532/6205/misccompilationtwo524xf9.flv.th.jpg[/img]

Frank46 · « **Reply #9 on:** June 07, 2008, 07:05:53 PM »

Well here goes. Not knowing the construction of the reinforcing bands I'd say they were sort of an interferance fit to prevent the bands
from slipping out of place when they were shrink fit on to the tube. Just my guess for what ever its worth. Sort of like the splines on outboard motor shafts. Frank

Double D · « **Reply #10 on:** June 07, 2008, 07:32:29 PM »

Okay, you don't like my idea...might not be to far off...but if any one might know iti s this Gentlemen.

W. S. (Bill) Curtis, ACII
Vice President, The Crimean War Research Society
Asst. Curator, Museum of the NRA (GB)
The Whitworth Rifle Research Project
MLAGB, HBSA

I have his email address on desktop computer in stoarge. I looked around a bit but couldn't find his email address real fast online.

You might post this picture over on the British Militaria Forum under General Interest> British Militaria and History. Bill Curtis visits that forum quite frequently. You could also send him a PM over there. He has had some recent post in the British Flint and Percussion Arms section. Find a post by him and then click on his user name and select send message.

cannonmn · « **Reply #11 on:** June 07, 2008, 10:30:02 PM »

Gentlemen, did either of you get the numbers from the 9" Dahlgren gun in the video clip? I can probably call them and find out but thought you may have gotten that info or may know something about that particular tube? Did the museum just get it or were they just relocating it to a new display stand?

Back to the grooves and the theory of aiding in lifting with ropes (we call 'em lines in the Navy) I doubt that was the reason because if you are lifting with a noose of almost any material, you WANT the line or rope to slip in just the direction those grooves would resist. You want the noose or eye to tighten without interference. If the grooves were put in there to keep lines or ropes from slipping off, they would have been cut perpendicular to the direction you see now, in my opinion.

I lifted a 10,000 lb. 8" Columbiad tube and I had to think about those things a lot to avoid big problems. I lifted the muzzle using a noose around a timber I put down the bore, so the noose could not slip past the muzzle. I liifted the muzzle using an "A" frame made out of two 6x8 PT beams. The breech was sitting on the ground at first, then when the muzzle was elevated a bit, we put blocks under the trunnions. With the trunnions as the new pivot point, just a little downward pressure on the muzzle timber would cause the breech to raise, so we could put blocks under it. Then we'd lift the muzzle again using a chain hoist from the top of the "A" frame .

A.Roads · « **Reply #12 on:** June 08, 2008, 12:05:02 AM »

Hi Mike & Tracy,
I must say that I envy you guys your wonderful line of work! If you describe the piece by bore size & weight it may help those of British ordnance interest to know which barrel you have, for example 7 inch of 7 tons, etc, the Brits had stopped identification by projectile weight by the period of this gun. Though I assume that this is a commercially produced barrel & therefore that it may not necessarily conform to a pattern adopted by the British military forces anyway.
The grooves you refer to were to prevent the slippage of handspikes when working the gun, this requirement disappeared on heavy guns with the introduction of elevating racks. Referenced "Treatise on the Construction and Manufacture of Ordnance in the British Service". Hope that helps, Adrian.

Victor3 · « **Reply #13 on:** June 08, 2008, 02:37:33 AM »

Don't yoos guys know nut'n?

Them grooves is there to make it easy to strike yer match fer to light the dang thing off

KABAR2 · « **Reply #14 on:** June 08, 2008, 03:22:26 AM »

Quote from: A.Roads on June 08, 2008, 12:05:02 AM

Hi Mike & Tracy,
I must say that I envy you guys your wonderful line of work! If you describe the piece by bore size & weight it may help those of British ordnance interest to know which barrel you have, for example 7 inch of 7 tons, etc, the Brits had stopped identification by projectile weight by the period of this gun. Though I assume that this is a commercially produced barrel & therefore that it may not necessarily conform to a pattern adopted by the British military forces anyway.
The grooves you refer to were to prevent the slippage of handspikes when working the gun, this requirement disappeared on heavy guns with the introduction of elevating racks. Referenced "Treatise on the Construction and Manufacture of Ordnance in the British Service". Hope that helps, Adrian.

Sounds like we have a winner!

Quote from: Victor3 on June 08, 2008, 02:37:33 AM

Don't yoos guys know nut'n?

Them grooves is there to make it easy to strike yer match fer to light the dang thing off

No you don't light it with a match......... eveyone knows you light you cigar with the match and light the "dang thing off" with that!

cannonmn · « **Reply #15 on:** June 08, 2008, 03:40:14 AM »

Quote

The grooves you refer to were to prevent the slippage of handspikes when working the gun, this requirement disappeared on heavy guns with the introduction of elevating racks. Referenced "Treatise on the Construction and Manufacture of Ordnance in the British Service". Hope that helps, Adrian.

Thanks Adrian. If you've got that book, it might be worth posting an exact quote of that section. I hate to take issue with anything that's "printed" but the grooves on that Armstrong gun don't look like they'd help very much in elevating the tube.

seacoastartillery · « **Reply #16 on:** June 08, 2008, 08:06:12 AM »

Thanks to all who have posted for your interesting ideas. And, we would be remiss here if we did not give Tim some credit for the Presentation Model idea. Many, many people think that this particular gun was exactly that, what with a rosewood upper carriage and large, beautiful bronze brake-actuating hand-wheels, etc. And a special thanks to Double D for the British Militaria Forum information.

Cannonman, sounds like you have some really illuminating experience lifting one of these heavy beasts! Wish we could have been there to help with that. We found this clip on the internet about 3 years ago and have no idea who did the moving or any particulars on the gun. Every historical photo we have seen used your method of securing a lifting 'line' to a stout pole placed in the bore. Definitely a No-Slip rigging solution.

Victor3, very clever! Actually the shape is correct if your match-head was the size of a pine knot!

We are pretty sure that KABAR2 is correct, and that A.Roads, Adrian, may have the best answer. The pictures posted below will help you make up your minds as to whose theory is correct.

Frank46, thanks for you input. We think you have a friend in cannonmn.

These photos show that a quoin was used on this gun which made handspikes essential. An elevating screw and capstan was used for fine elevation adjustment and raised the pivoting iron plate which supported the quoin to a certain extent. The quoin was used for gross elevation movements as the handspikes lifted the tube's breech. Also you can see in the photo of Tracy and Mike shivering in the 40 deg. with 25 mph wind weather at Fort Fisher, North Carolina in December of 2005, that the edges of the upper carriage cheeks are shod with iron straps. These would prevent the prying action of the handspikes from crushing that beautiful rosewood!

Any body have a completely different theory?

Tracy and Mike

cannonmn · « **Reply #17 on:** June 08, 2008, 10:02:59 AM »

Thanks for posting the trunnion marks, that adds an important bit of info, the fact that the preponderance of the breech is 809 lbs. So if handspikes were a required part of elevating the gun they would need to press upward with a force of 809 lbs, not too much of a load.

Assuming you used two handspikes on opposite sides and each had a leverage of 4:1, the crewman on each handspike would need to push downward with force of f=809/(2x4)= 809/8

so f=101 lbs. approx.

I don't know the exact geometry but assuming a handspike is 5' long, having one foot over the fulcrum and four feet outside the carriage is probably a fair estimate, but if there's only 6" of handspike inside the carriage beyond the fulcrum, the handspike only needs 50 lbs. of force on the handle, which sounds like a more reasonable estimate for your average young, underfed Confederate artilleryman who might weigh 90 lbs. soaking wet.

seacoastartillery · « **Reply #18 on:** June 08, 2008, 11:31:37 AM »

Thanks John, for that information on the relationship between the preponderance of this tube and the handspike lifting force. There is a pretty good historic photo on our website under North Carolina on the Photo Gallery Menu which shows the gun right after cessation of hostilities in January of 1865. The very long 10 or 11 foot roller handspikes are in view and also another set of shorter ones which could easily be 6 to 7 feet long. This extra length would help those Confederate artillerymen get the job done even if they had a full foot past the fulcrum.

Regards,

Tracy and Mike

A.Roads · « **Reply #19 on:** June 08, 2008, 11:51:33 AM »

Thanks for posting the additional images, a fine & interesting piece of ordnance.

Its Weight.
15,737 lbs equates to 7.02 tons, the British used 7 ton guns in 7 inch calibre so I'm assuming that this is most likely of that calibre. Its external profile does not conform to their Mk I, Mk II or Mk III patterns, although it is most similar in construction method to the Mk I, predating the Fraser system of using fewer & larger pieces to build up the gun.
In fact dated 1864 it is quite an early example, the British introduced the 7 inch 7 tons gun (Mk I) in 1865.

Its Preponderance.
The British military were unsettled on the question of preponderance for some time. For example in 1865 it was decided that 8 & 9 inch guns should be completed with no preponderance. Then in 1867 it was objected that the muzzles drooped when loading, under the weight of the projectile, & didn't follow down for elevation. It was therefore approved that the preponderance of 7 inch guns (of both 6 1/2 & 7 tons) would be 3 cwt (336 lbs), 8 inch 4 cwt, 9 inch 5 cwt & for guns above 12 tons no more than 6 cwt & no less than 5 cwt preponderance.
Later, in 1869, the Admiralty requested that guns of 18 tons & more should have no preponderance, but as this was virtually impossible anything under 3 cwt was considered as nil.
So at 809 lbs the preponderance on your gun is quite heavy & it was such early guns, with heavy preponderance difficult to elevate with handspikes, that raised the whole issue of preponderance soon after.

The Mysterious Grooves.
These were definitely for use with handspikes, they are perfectly placed both on the breech of the piece & in relation to the carriage for this.

Also official contemporary writings, quoted as requested:
Some quotes from "Note book of Construction & Manufacture of the Rifled Ordnance in the British Service" 1872.
regarding preponderance:

pp. 114
"but it was also stated 'that the preponderance of 7-inch guns renders depression with handspikes difficult'.

pp. 125
"To prevent the handspikes slipping when working the gun, the breech is scoured underneath at each side and at the end"

From "Treatise on the Construction & Manufacture of Ordnance in the British Service" 1877.

pp. 189
"To prevent the handspikes slipping when working the gun, the breech was formerly scored underneath at each side. This is no longer required, as heavy guns are now elevated by means of elevating racks."

This is the first time I have seen examples of such marks. Adrian.

cannonmn · « **Reply #20 on:** June 08, 2008, 01:04:11 PM »

Thanks for the quotes. So now we have an "offishul" name for that process: "scouring." Never in a million years would I have guessed what scouring meant in this context.

gulfcoastblackpowder · « **Reply #21 on:** June 08, 2008, 04:51:41 PM »

Quote from: seacoastartillery on June 07, 2008, 06:40:40 PM

We believe that the grooves were placed where they are to prevent hoisting rope slippage during a garrison gin lift or a dockside crane lift from or to the deck of a ship. so, what do YOU think?

That's exactly what I thought when I saw them. Not that I can confirm it's validity, but it seems the most probable explanation to me.

Frank46 · « **Reply #22 on:** June 08, 2008, 05:38:21 PM »

Mike & Tracey Cannonman is my hero. I may never be able to afford toys such as his, but through his and others videos here and on utube I can enjoy the bangs and booms as if they were my own. I'm sure glad someone asked how he can afford such toys. Come to think on it, there is a method to his madness. That was as a compliment so I sure hope Cannonman or anyone else takes offense.
And it sure would shock the folks around here to see me towing a cannon with the tractor. Again to all, thanks for sharing. Note, found an error in my sentence. So my origional intent regarding it being a compliment still stands. Darned CRS again. Frank

seacoastartillery · « **Reply #23 on:** June 08, 2008, 06:36:20 PM »

Adrian, Thanks so very much for posting those quotes. We are quite sure that the truth about the purpose of those mysterious Armstrong grooves therein lies. As much as we are fond of being right, we are far more fond of finding the truth. After all, a non-skid surface for the breech-lifting handspike is a noble purpose. It helps to save the artillerymen from injury and it also helps prevent damage to their equipment. It might possibly help prevent rope slippage after the gin rope and end loop are properly placed slightly off center prior to the application of the load. Another clue that we found just above these grooves directly in line with the lifting line is the left and right rear sight holders. Both of them have the bottom edges completely filed off and the edges are sanded and polished a bit too. Why would Armstrong's artificers do this extra work? We believe it is to keep the edges from cutting the garrison gin lifting rope; it certainly wasn't for the sake of appearance, because this modification is downright ugly. Take a look at these photos below.

Gulfcoastblackpowder, Read Adrian's quotes as to the stated purpose of the grooves. This, we believe is most certainly the designer's primary purpose.

Frank, we like those video clips too. Someday maybe he will drag his 8" Columbiad out there and show us what full-size grapeshot will do!! Now THAT would be really something!

Regards,

Mike and Tracy

A.Roads · « **Reply #24 on:** June 09, 2008, 01:19:01 AM »

Hi Mike & Tracy,
Interstingly I read only just the other week that the sight holes were smoothed out otherwise the edges were found to be liable to get knocked out of true. The sights were removed when not in use & were difficult to fit back if the holes had been thus injured. This was probably more of an issue on the smaller more mobile natures than heavy static fortification pieces. The smoothing described would be at the top, so I think that the bottom was smoothed as much to prevent damage to hoisting gear as you suggest. Adrian.

Frank46 · « **Reply #25 on:** June 09, 2008, 06:54:32 PM »

Mike and Tracey, yep sure would like to see Cannonman's 8" colombiad in action. Are you sure drag is the right term?. Would need a crane at least. Cannonman, hint, hint. Frank