another New to cannon building

[guzzibill]

Hi, My name is Bill and I am building my second cannon. I have a question or two that I need input on. My barrel is 23 inches long, DOM hot formed seamless tube, 2.5 inch bore, .75 inch wall thickness. I had the breach end plugged with a 3 inch piece of bar stock, machined to be a " heat the barrel to allow the plug to be pressed in" fit. I had it recessed into the tube by about 3/8's and then had the whole end filled with weld. then I had it machined flat and had a 1.5 inch slab of steel welded to the end of the breach, covering the welded in plug. Next I had a 1 inch hole drilled through the tube and plug, and pressed in a pin to fit, barrel heated first as with the breach plug, leaving a 1/4 inch space on each side that was filled with weld. the first six inches of the breach were left the original O.D. size (4 inch) ( a small amount was turned off to clean the welds where the slab at the end and the filler welds at the pin were. At the six inch point, the barrel taper was started, ending at the muzzel with 3/8 wall.  Trunions were cut from 2 inch bar stock, radiused to fit the barrel, the stepped down to 1 inch. the trunions were drilled in the radiused center and a roll pin was pressed in to leave  1/8 protruding, and the barrel was drilled to match, these were just locator pins to insure that when they get welded, they are where they are supposed to be. vent hole will be a musket nipple and cannon lock arangment.
 First queation.... is the 3/4 inch wall thickness enough to be safe ?
 second question... will just welding the trunions be enough ??
 Thanks for your collective wisdom... this is my first post to this forum.

http://www.flickr.com/photos/19323179@N03/sets/72157617492288040/

[Cat Whisperer]

Hi, My name is Bill and I am building my second cannon.
...

Bill - WELCOME to the board!

Great opening line.  It usually goes, 'Hi, My name is Bill and I too have an addiction.'   

Great lookin' cannon too!

3/4" is OK, but it needs a powder chamber.

Standard rule of thumb is that the diameter of where the powder is should be surrounded by an equal dimension of steel all around and behind.  The pressure spike is right at first.  Once past that the gasses are expanding, pushing the ball down the tube and the pressure is MUCH less (therefore the 3/4" wall thickness is ok).

It still can be done by using a LONG drill/boring bar.

[Victor3]

 I think the best bet to make a chamber at this point would be to go through the rear (cascabel ball doesn't appear to be welded on yet?). Bore a through hole the size of the chamber required and shrink-fit/weld a plug in. There's ~4.5" length of steel at the breech, so enough to machine a large enough chamber yet still have a plug long enough for safety.

 If it were mine, I'd shrink a sleeve over the OD to make a Parrott style bbl.

 Aside from the above, it would be safe as is for a pool ball (2.25" dia) and ~200 grains of FG. I wouldn't chance anything much heavier though.

 Trunnion diameter is a little small at 1", but should be OK if materials for both tube and trunnions are compatable for welding, are welded properly, and no really hefty loads are used.

[Double D]

As Cat Whisperer pointed out you cannon does not conform to the recommend safety standards for wall thickness over the chamber.  You have a 2.5 inch bore and the standards call for a minimum wall thickness of 2.5 inches over the chamber.  The diameter of your barrel over the chamber should  7 1/2 inches to meet the recommended safety standards.  

You could make a chamber of no more than 1.3 inches in diameter and no more than 1.6 inch deep in the breech plug and be okay

The breech plug sounds over built and we say here on this board, overbuilt is always good.

Trunnion attachment sounds okay. But Trunnion rule of thumb is same dimaeter of the bore, 2.5 inches.

[guzzibill]

Thanks for your input... I wish I had waited to read it before I went to the welder today... it has been welded up, trunions ( 2 inch where they contact and are welded to the barrel, then stepped down to _ 1.5 _ inch, not 1 inch as I had posted at first) and casabel are now part of the barrel. my first cannon was a six foot barrel, beer can bore, .75 seamless stainless plugged in the same fashion as this one, but sleaved like a parrot with another 3/4 inch of steel. flash suppressor, acme elevation screw, military jeep wheels and tires, 2 inch receiver hitch, tail lights and a plate. I also have a golfball cannon, steel liner cast in a 2/3 scale mountain Howitzer profile in aluminum that was bought at a gun show. my point is, neither the golf ball or beer can barrel has a chamber... just flat plug. how do you get a smaller charge into the chamber hole its easy with no chamber, I just make a ball of powder with a baggie and foil to fit the bore and press it home. then whatever I am shooting gets pressed home ... then prick it and fuse it... they both have seen hundreds of shots with no sign of trouble.
 HOWEVER... I am not against learning to do it better and safer...making a chamber for this gun is still an option, as is sleaving the breach.  if I sleave the breach, do I still need a chamber smaller than bore size ?? I am so confused... I usually use a 35mm film can of cannon grade for the golf ball cannon, and two of them for the beer can version... how many grains is a 35mm film can ??/ am I just lucky or am I in the ballpark ??. lord knows I want to not kill or maim anybody.... I will have to post the story of my trip to the DMV to get a license for the big one... funny stuff.

[GGaskill]

if I sleeve the breach, do I still need a chamber smaller than bore size ??

No, if you sleeve such that the total wall thickness over the chamber area is 2.5", you would be OK (that's going to be awful heavy.)  Right now you are 4" in diameter; I would say if you shrink fit an additional inch and a half, you would be OK.

[Ex 49'er]

On my digital scale a 35mm film canister of powder weighs 495 grains.
Did the DMV person have a cow?

[Victor3]

"...how do you get a smaller charge into the chamber hole?"

 One method is to use a long copper tube that can be inserted down the bore and into the chamber. Then using a long dowel, push the charge in. Then remove tube/dowel and load ball.

"...they both have seen hundreds of shots with no sign of trouble."

 That may be so. But with time, repeated use, corrosion, stress, etc, cannons do not retain their original strength. That's why the rule of thumb preached here is to compensate for potential future problems by building barrels stronger than they need to be for today's safe use.

 These things we make will probably be around long after we're gone. Not many people will see a nice looking cannon barrel like yours and just toss it in the trash. We should be reasonably assured that someone 50 years from now (might even be a Grandson as far as we know) will be safe using them.

[guzzibill]

OK, so if I make a 1.33  inch by 1 .6 inch chamber ( or 1.5 X 1.5 ), and the bore is 2.5, will the chamber hold enough powder to support the ball size, or would it be a wimpy charge for the bore ?? ,  I really want to keeep the profile  the barrel has now, and not band it like a parrot. normaly I will shoot LaCross balls, but I will shoot cement filled cans and steel balls on occation...

[Double D]

OK, so if I make a 1.33  inch by 1 .6 inch chamber ( or 1.5 X 1.5 ), and the bore is 2.5, will the chamber hold enough powder to support the ball size, or would it be a wimpy charge for the bore ?? , ...

Define wimpy.

[Ex 49'er]

Get a chunk of wood and bore it out to the proposed dimensions of the powder chamber and then fill it up with powder.
Weigh the charge and see how much you have stuffed in it.

[Victor3]

OK, so if I make a 1.33  inch by 1 .6 inch chamber ( or 1.5 X 1.5 ), and the bore is 2.5, will the chamber hold enough powder to support the ball size, or would it be a wimpy charge for the bore ?? ,  I really want to keeep the profile  the barrel has now, and not band it like a parrot. normaly I will shoot LaCross balls, but I will shoot cement filled cans and steel balls on occation...

 A 1.5" x 1.5" chamber will hold ~750 grains of FG. That will put a 5oz LaCrosse ball into low earth orbit. However, they're 2.5" diameter and made of rubber. You won't have any windage (clearance) in your barrel, and the ball will deform in the bore upon firing. I'm not sure how safe that would be; you don't want to create a bore plug with them.

 I'd stick with a cement filled can with correct windage for your bore. 750 grains of FG would be a substantial, yet safe charge in your barrel (assuming the 1.5 x 1.5 chamber) using that as a projectile.

[Double D]

If you refer to our Safe loads and cannon plans sticky at the top of the forum you will find Matt Switlik's chart for safe loads for small guns.  That chart list 500 grains as a maximum safe load for 1 1/2 inch bore. Remember in mortars and howitzer the bore diameter for determining powder charges, is the diameter of the powder chamber.

What I would do is drill an 1 1/2 inch hole in piece of wood until it is just deep enough to hold 500 grains. Measure that depth and use that as the depth of your powder chamber.     By doing this you are building in a element of safety for you and the next guy to own this gun.

[guzzibill]

Define wimpy.



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 A fat guy with a bowler hat thats three sizes to small and a fuzzy mustash that mooches hamburgers...

But I digress...  I want the cannon to act like a cannon... shoot the ball farther than I can see, with LOUD blast and a lot of smoke. The tube I used for the barrel is about 2.5 I.D., I didnt mic it, but a LaCross ball rolls down the barrel with no help... and it has a little windage... a little. I am thinking that at this point  ( barrel is for all intents  finished, minus vent and chamber. my new and improved brainstorm is to get a piece or bar stock, have it turned to tight heat/ press fit of bore, and have it bored to 1.5, by 1.5 deep and cut it off leaving about 1/8 of material at the end. So I would have a closed end "chamber"  1 & 5/8 long... I could then use some industrial epoxy on the closed end and press it home in the heated barrel. at that point I could vent it. which brings me to another question.... will a musket nipple and cap set up fire the cannon reliabliy ? do you drill the hole for the nipple all the way through to the chamber the same size as the hole needs to be for the tap for the nipple ?. Or do I just drill the vent hole smaller ( like, maybe fuse size) then make the first 1/4 inch larger for the tap ?  I have heard people use Hilti blanks ( powder accuated tool charges...22 - .25 cal) are these better / worse ??  the wall will be 1.25 thick, and I have no experance with nipples and caps... is that to far for them to reach to be reliable ?    I was also thinking that I could drill and tap a 3/8 hole all the way threw to the chamber and rund a brass bolt all the way to the chamber ( with hi strengh locktite)  then drill the brass for the vent... it would add a little extra to make sure the chamber didnt budge. what do you think ??     

[dan610324]

isnt the idea with the nipple and cap to get a "jet stream" with hot gasses that ignite the main charge ??
I would guess that a 1/16" hole from the nipple and down would be good , at least its easier to enlarge it if needed then to make it smaller

what do you guys with experiance from cap fired cannons say ??

[Double D]

 
But I digress...  I want the cannon to act like a cannon... shoot the ball farther than I can see, with LOUD blast and a lot of smoke. my new and improved brainstorm is to get a piece or bar stock, have it turned to tight heat/ press fit of bore, and have it bored to 1.5, by 1.5 deep and cut it off leaving about 1/8 of material at the end. So I would have a closed end "chamber"  1 & 5/8 long... I could then use some industrial epoxy on the closed end and press it home in the heated barrel. at that point I could vent it. which brings me to another question.

There are four levels of cannon shooting.  The first is designing and building a safe cannon.  This is where you are now.  I am not comfortable with the idea of shrinking an insert in from the muzzle, but I guess in a way it's no different than shrinking in a breech plug from the back.  When you drill your vent you are going need a vent plug- a tube that runs from the outside of the cannon to the inner chamber.  The plug will give a continuous liner to the bore and will cover the seam between your insert and barrel.  This seam is susceptible collecting debris and can be site of corrosion that you cannot clean or see.

The other thing you need to establish is how much powder the chamber hold.  I will repeat what I said up thread

“That chart list 500 grains as a maximum safe load for 1 1/2 inch bore. Remember in mortars and howitzer the bore diameter for determining powder charges, is the diameter of the powder chamber. What I would do is drill a 1 1/2 inch hole in piece of wood until it is just deep enough to hold 500 grains. Measure that depth and use that as the depth of your powder chamber.     By doing this you are building in an element of safety for you and the next guy to own this gun

Second level is firing and the inclination is the load up the cannon with as much powder as you can and shoot the ball further than you can see.  This is the most dangerous level.  If you can't see the ball hit then you have no way to know it landed in a safe spot. Also at this stage without safe design you cannon can break, especially if you use excessive loads. 

The third level is achieved when you decide that flinging balls into outer space and not seeing them hit is boring. Actually if you don't see the impact of the ball you loose 1/3 of the fun of shooting--Blast-Smoke-Impact.  That's how a cannon acts and I love!!!     This can be real fun and you may not achieve the desire to go to the fourth level...some do and some don't.

The fourth level is hitting something with your cannon.  This is where the fun begins. Here is Battery I for Iron that we will shoot at the Montana cannon shoot.  Think you can hit one of these at 100 yard?



How about the guns of Battery G for Graveyard, they will be the 50 yards.



How big are they?



I'll let some one more familiar with the use of musket nipple discuss that

[Victor3]

 You might have trouble getting a solid joint by making a new chamber piece and shrink-fitting it in way down at the bottom of the bore.
 
 For one thing, the fit has to be fairly precise, and the bore very round (this usually means it has to be lathe bored). Measuring the bore at the muzzle will not tell you what the diameter and cylindricity is down near the plug, especially considering the machining/welding that has been done on the tube already. I guarantee you there will be at least a slight restriction at the point the trunnions were welded. If the chamber piece get's stuck on the way down and you can't get it in place before the tube cools, you're done.

 An alternate method would be to make the new chamber piece a tight slip-fit, drill a few small holes through the wall of the tube and solder the piece in place by introducing solder through the holes. I've seen this done on a similar assembly. It was done by the most experienced welding guy I've ever known though; it took some special soldering voodoo that I'm not ordained to do.

 I still think (even if you have to cut off the cascabel and weld it back on) that boring through the rear and re-plugging would be the most viable way to create a chamber.

[guzzibill]

Thanks to all of you that weighed in on my cannon design. I decided to go with the suggestion of a 1.33 chamber, 1.6 deep + the small amount extra that a boring bar leaves at the bottom , bored into the existing plug. ( the boring bar is just a long piece of steel, with a carbide tip, set at a 45 degree angle, so it leaves a "cone"  rising from the bottom of the hole, sort of like a regular drill bit in reverse, as it leaves a cone going deeper into the material.) so the chamber will be 1.6 from the mouth  to the tip of the cone.         ================================
                     -
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 -
   -
    -       <--- this is what the bottom of the chamber will look like
   -                in cut away.
 -
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                    -
                    ===========================================                   
I considered the suggestion of cutting off the casabel and boring in from the rear, but didnt want to mess with mostly finished profile of the barrel and the integrity of the plug.
 I dont think the cone should pose a problem, but just in case I am going to either pour some epoxy in to fill the bottom level, or try and grind the cone away with something. on the other hand, a worm made to follow the cone to the edge would work great.
I pick it up from the gun driller tomorrow, then take it to the powder coater... if I can decide on a color.... Gloss black, Satin black... Brass,  Antique Bronze.... O.D. green, Kaki, digital desert camo  ... to many choices...
 Any suggestions ??
the carriage is Oak, medium rough sawn finish, with medium walnut tung oil, all dressed in black wrought iron. wheels are Amish hand made heavy duty Cannon wheels... also rubbed with the tung oil. Thanks again everybody , for letting me sleep well when this is finished....