Use Cannons...You can ask all about me !!!

[cannonmn]

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What about my breech?

I for one, would not be able to comment on that breechloader because I don't know enough about its design, I can't see inside and don't know exactly what materials were used, what processes, etc.  I think it would take a thorough inspection and a lot of questions before I'd feel comfortable about making any judgments on it.

There are a number of things that design does that are quite a bit different from the all-metal cannons we usually discuss here.  The "Lion's Paw" design transfers some large forces onto the wood of the carriage, forces which would tend to separate the breech from the barrel with force calculated by (chamber pressure) X (area).  In the case of a golf-ball-sized bore, assuming all the force is confined to the area of the bore (not necessarily the case in the design I see) then, assuming a modest 15,000 psi blackpowder chamber pressure, the linear force which wants to push the breech away from the barrel is:  f=(a)X (p) =(2.14 square inches) X (15,000 psi) = 32,100 pounds.  I don't think the wood will resist this force.  You can see why most of these early breechloader designs have a metal breech housing connecting the barrel and the removeable breech.

Reminds me of the song that goes "16 tons and what do you get..."
A pile of splinters is what I'll bet.

[dan610324]

yeah cannonmn , you are probably right .
but in this case its an authentic replica ( or almost authentic ) of an nearly 550 year old cannon .
and that's how the early guns was designed , safe or not ??  absolutely not by our standards .
but an extremely interesting cannon from an historic point of view ,
probably an nice noise maker   

[thelionspaw]

Thank you for the prompt response.

Question: How much pressure would be generated by 1 1/4 oz  of Fg in a chamber 1 3/4" across and 3 7/8" deep, considering that the charge is confined in 4 ply heavy duty foil, seated in a  chamber with a 7/8" wall and the charge taking-up only a fraction of the chamber?

nb: the block face (bolt face) is not seated into the tube or onto the projectile with zero tolerance; ergo chamber pressure is considerably relieved, minimizing the rearward thrust of the breechblock.

This is and was always an inherent problem (escaping pressure) in the function and design incorporated by wrought iron breechblock machines.

Failure seems to historically be confined to the actual powder chamber and not the stock.  The tube itself was by design (laminate) from what I have read, that was the favourable strong point in construction. It was able to withstand pressure better than cast metal.

The butt of the Lion's Paw's breechblock is 5" and thrusts against a 2 1/4" wedge which seats on a 4 1/2" steel plate that butts against 4 pieces of laminated and doweled 1 1/2" stock with a finished surface of 6".

Is that enough for a computation?

nb: The entire powder chamber of the breechblock (with its 7/8" wall) is encased in a barrel chamber with a .337 wall and a reinforce band of .250 99,400 psi steel.

What do you think?

Richard

[cannonmn]

 >its an authentic replica ( or almost authentic ) of an nearly 550 year old cannon .
and that's how the early guns was designed , safe or not ?? 

Remember they all used serpentine powder, which was MUCH less powerful than the corned powder we use today, and I think much slower burning.

If someone is determined to shoot a weapon such as the LP, I recommend they make their own serpentine powder to load it with, and NOT use modern corned (granulated) powder.  I think both authenticity and safety will be served.

Calculations of force are easy, just figure out exactly where the pressure will be exerted and multiply pressure times area, making sure first that units are all in same system of measure, and doing a dry run of the formula to make sure the resulting unit of measure is in a force measure (such as pounds) which is achieved when the "units cancel" while doing the math.

[thelionspaw]

Corned powder came about circa 1450 and wrought iron barrel-stave construction continued well after that. As a fact, Canadian blacksmiths in Montreal were forging breechblock during the Seven Years War (1760's), that used corned powder.

Large caliber breechblock cannon were fitted with a wooden stock as per my example.  Smaller caliber Serpentine and Falconet were often fitted with a metal stock; not as much for strength, as for bulk or lack therof. A swivel gun on the rail of a ship or wall of a stockade, would have been cumbersome with wood and so they were made manageable with metal.

My 64 mm Falcon is copied from a 105mm piece from 1470-1480 in Bohemia, a leading area for artillery inovation and design, during and after the Hussite wars.

Now what I have reproduced with "modern steel" is a 64mm patterened after a 105mm that had a wooden stock and used corned powder. The difference is that the original design is for at least a 4 1/8"  tube and I at present, have only 2 1/2" tube. My construction is stronger and the charge and caliber are greatly reduced but using the same design.

That which is tennis ball size now at 64 mm, is paterned after a 105 mm and it is being further reduced to a golf ball 1.68 mm..

I use 1 1/4 oz of Fg on average to propell a missile (albeit a tennis ball) and a maximum of 2 1/2 oz for blanks. Normally, no more than 2 oz are used for blanks. I can boost the charge for a missile too and still sip my tea next to it. Alcohol and gun powder do not mix well.

I am a piker when it comes to using powder by black powder  cannon standards but the report is deafening, the flame is awsome enough for me and the wood never splinters and the metal never flies. My Lion's Paw is over-built.  I use a scant ounce plus, whereas others deal in more than a pound.

Now if someone can tell me where I can buy a seamless sleeve that is 32" long with an OD of 2 7/16" and 3/8" wall, leaving me with an ID of  at least 1.68"  I will be eternally grateful.

Thank you for the formula. It gives me something to begin working with.

Oh! and my camera should have some images of the Lion roaring this weekend that I will add to my "15th c. wrought iron breechblock Falcon 2 pdr" thread.

Thanks again,
Richard (a.k.a. 3 fingers Brown)

[Cat Whisperer]

how about the radius in the bottom of the bore , is that an must ??
or is it enough with the 118 degree angle that it is on the tip of an drill bit ??
...

The full radius is the strongest.
No radius (i.e.: sharp corner at 90d or some other angle) puts all the stresses right into the corner.
By using some radius one spreads the stresses over a wider area, hence lowering the stresses at any given point.

[dan610324]

yes of course an full radius reduces the stress in an particular area , but is it an absolutely must in an solid steel cannon to have it approved by the NSSA ??

[Victor3]

"Now if someone can tell me where I can buy a seamless sleeve that is 32" long with an OD of 2 7/16" and 3/8" wall, leaving me with an ID of  at least 1.68"  I will be eternally grateful."

 You might have trouble finding seamless tubing in that size

 However, if your bore is actually at least 64mm (2.52") Jorgensen (EMJ) can supply 4130 cold drawn seamless in 2.5" x .375 wall, leaving you with a 1.75" bore (1.75" bores are often used for golf ball cannons. 1.68" is a wee bit tight).

[Double D]

yes of course an full radius reduces the stress in an particular area , but is it an absolutely must in an solid steel cannon to have it approved by the NSSA ??

Two different requirements. 

The rounded corner that Tim always refers to-the stress riser doesn't not have to be that  radical.  It is there to relive and distribute stress in the corners on items the might be subject to stress, usually on outside corners but sometimes on inside corners.  The sharp corner focalizes that stress in that corner.

In N-SSA rules they want a radius so there is no sharp corner to make it easier to clean the bore and not leave any spark bearing material behind.

[TexasWolf]

Hey Y'all,

I am editing my original post..   I didn't mean for my post to appear as a commercial post, I was just trying to add some news/information regarding the discussion of the seamless vs welded barrel liner in the Osvaldo Gatto Mountain Howitzer.

My brother bought his first cannon, the Mountain Howitzer from Osvaldo Gatto. Largely as a result of the correspondence between my brother and Osvaldo, and in part to the discussions from those of you on this very forum, Osvaldo has modified the production of the Mountain Howitzer and has introduced a new model which is  now manufactured with a seamless steel barrel liner. He sent us the schematic for the new barrel design and I am linking it below.

http://lonestarartillery.com/IMAGES/PRODUCTS/MH001/seamless.sleeve.diagram.v3.jpg

Cheers Y'all,

Rob "TexasWolf"

p.s. We took the Mountain Howitzer out for test firing this last weekend, July 4th 2008 near El Paso. I put a link to it towards the top of our webpage if you want to try the streaming video of it.. is at LoneStarArtillery.com

[dan610324]

you guys are sure lucky , mr Gatto makes wounderful guns .
if I lived in the usa I would have tried to get it myself.
and Im very happy that you think about the safety .