Author Topic: homebuilt cannon (Read 1760 times)

rick1986 · « **on:** April 16, 2012, 07:15:13 PM »

Hi, my name is Rick and I would like some help with a cannon I built. Its nothing fancy, just usable. I started with a 45" piece of 3" seamless DOM tube, and welded a piece of 2 and 7/8 shaft in the end. Then I beveled the edge of the cannon, and the edge of a 3/4" thick piece of flat metal and welded that on the end. I put 1 and 1/2" trunions on the side, and mounted it on an axle. I shoot a 2 and 7/8 shaft 3" long, which weighs about 10 lbs. I use 1500 grains of Pyrodex and light it with a fuse. The powder is about 1/2" thick and 3" in diameter, which is the diameter of the tube. That 10 lb chunk of steel drops about 10 feet in 400 yards. I have no rifling or fins. I did no research before I built this cannon, and by reading your forums and other information I realized this is unsafe. What would be the best way to remake the end of my cannon so it is safe? Do I need to make a powder chamber for a more efficient burn, or can I just press a piece of 1 and 1/2" wall seamless 4" long on the end and weld an 1/1/2" plate on the back and call it good? If I needed to I cud press a machined shaft in the ind and then weld the plate on for more strength. Also, where can I get a reliable chart telling how much Pyrodex I can use in a 3" bore? You guys will probably tell me that cannon should have blown up. Thanks in advance

GGaskill · « **Reply #1 on:** April 16, 2012, 07:50:30 PM »

It would help if you gave us the inside and outside diameters of the barrel for starters. Second, I would reduce the weight of your charge by 50%.

Probably you can shrink on an additional tube over the powder area to give you enough strength and safety but we need more data.

Just for some numbers, the 3" Parrott rifle's reinforcing sleeve was 11.375" in diameter. The 3" Ordnance rifle (which was wrought iron instead of cast iron) was 9.7" in diameter at the front of the chamber.

Cat Whisperer · « **Reply #2 on:** April 17, 2012, 02:14:33 AM »

Rick -
What an incredibly mature approach! Too many folks are of the attitude of "I built it and fired it therefore it is safe".

A drawing - paper and pencil - with some dimensions would be useful - there may be a reasonably easy way to sleeve it or as you mentioned to implement a powder chamber.

AND WELCOME to the board!

BoomLover · « **Reply #3 on:** April 17, 2012, 05:56:00 AM »

Welcome to the forum, Rick1986....great to have you here and starting off on the right foot by asking questions of these guys who have the knowledge you need! From your description, we do need more info, as Cat Whisperer said, but stick around, read the stickies at the top of the page, read, ask questions...your gonna like it here! BoomLover

rick1986 · « **Reply #4 on:** April 17, 2012, 04:53:01 PM »

The ID of my cannon is 3", and the OD is 41/2". Since I haven't the foggiest idea how to make a drawing with a paper and pencil and get it here, I will try to explain it better. Like I said, I took a 45" piece of 1026 DOM tube and put a piece of 2 7/8" cold rolled steel 3/4" long 3/8" deep in the end and welded it well. Then I beveled the edge of my cannon at a 30 degree angle, and also beveled the OD of a 5" piece of cold rolled shaft 3/4" thick. The vee I had when I put it on the end was 1" deep. Then I filled that whole groove up with weld.

Now, I am willing to cut the end off and start over if I need to. 4 1/2 ID 7"OD tube that I could press over the end is $70 an inch, so I was hoping to get by a little cheaper.

Another brain storm, could I take a piece of 8" cold rolled shaft and drill a powder chamber in the center, and then weld it to the end somehow? Thanks

GGaskill · « **Reply #5 on:** April 17, 2012, 05:40:58 PM »

Since I haven't the foggiest idea how to make a drawing with a paper and pencil and get it here, ...

The appropriate way is to scan it but if you don't have a scanner, then just take a sharp digital picture of it and post it at myhostedpics and then include it as an image in a post.

... and put a piece of 2 7/8" cold rolled steel 3/4" long 3/8" deep ...

I guess 3/8" deep means recessed 3/8" from the end. The 2 7/8" diameter concerns me as that is going to leave a groove around the plug where powder fouling will accumulate and eventually cause a failure from corrosion. I think that needs to be addressed.

4 1/2 ID 7"OD tube that I could press over the end is $70 an inch ...

That sounds awfully expensive. Even though you wouldn't need more than maybe 6 or 7 inches. I gather you are buying online.

... could I take a piece of 8" cold rolled shaft and drill a powder chamber in the center, and then weld it to the end somehow?

I like the previous idea of replacing the existing breech plug with a new one containing a chamber. But for that process to work well, you need a really tight fit between plug and tube with the plug a few thousandths larger than the bore. It is my guess that the bore is not perfectly round and would require at least a skim cut to true it.

Do you have a lathe big enough to hold the tube?

rick1986 · « **Reply #6 on:** April 17, 2012, 06:20:28 PM »

Yes, I meant that the breach plug would be 3/8" recessed in the end. And yes, that gap around the plug is beginning to bother me too. Another yes, I have a lathe large enough to true the end up. I also might be able to find some used iron cheaper that I could press over the end. I work at a metal shop, and I was just going to buy the tube from my boss, but maybe I should look online.

GGaskill · « **Reply #7 on:** April 17, 2012, 07:52:21 PM »

Don't know where you are but you should visit the metal/scrap yards yourself.

There are a couple of ways to deal with this that come to mind.

One is to saw off the existing breech, face the end and bore the breech for about 5" to a depth that cleans up all the way around. Measure the diameter and then turn a new breech plug .003" or .004" larger and bore a 1.5" chamber 3" deep in the plug and taper the bore end. Then press this into the tube to a tight fit against the shoulder created by the boring and weld the back (should chamfer both plug and tube for the weld. Weld in place. Then drill a hole for a vent liner so you will have a direct hole to the bore without a crack between the two parts that could collect fouling and corrosion. This is probably the cheapest way.

The other thought is to again cut off the existing breech, face the end, bore for about 3" to clean up, and fit a solid plug as above. Then shrink fit a sleeve over the outside that overlaps the powder area by at least an inch on both ends.

rick1986 · « **Reply #8 on:** April 19, 2012, 09:02:17 AM »

Ok that all sounds good. One question I had was what you meant when you said to taper the bore end. Do you mean just bevel the edge of the whole I bore in the piece of shaft so the powder can find its way it the chamber better? Or bevel the outside of the shaft to put it in the bore? How many grains should I build the powder chamber in the shaft to hold? And then how do I fill it? With a 1"pvc pipe? Also, I would like to ignite this cannon with a 509 inline muzzleloader primer. Should I drill a hole in the back or top of the chamber? Thanks in advance for your answers. I know very little about cannon building

GGaskill · « **Reply #9 on:** April 21, 2012, 11:16:07 AM »

The logic behind tapering the bore end of the plug is that the pressure from the explosion will tend to expand the plug against the tube and help keep fouling out of the joint. Do not chamfer the plug, though; chamfer the tube. In fact, the bevel for the weld will take care of easing the plug into the tube.

I am not familiar with the primer you refer to so I can't really comment on its use. A vent on bore center would eliminate the need of a vent liner since it would be going through only one piece of metal. However, it would cause vent debris to go directly to the rear instead of vertically over the gun, so additional care would be required when firing.

rick1986 · « **Reply #10 on:** April 25, 2012, 03:45:13 PM »

The primer I am talking about is basically a shotgun shell primer. A 1.5" hole 3" deep is only about 900 grains, is this enough? One place I was looking said for a 3" diameter barrel you could shoot 1750 grains. This is what I was going to make the plug to hold, but maybe thats way too much. Also, where is the best place to light the charge? If I lit it in the front, it would burn back and not waste any powder, and it would be a slower burn. If I lit it in the middle, some would blow forward and burn instantly, and the back would burn a little slower. I think this would be the fastest burn. If I lit it straight in from the back like a rifle, it seems that it would blow some out of the end before it got all the way burned. What is the reasoning behind lighting a rifle shell from the back? Thanks for t advice.

GGaskill · « **Reply #11 on:** April 25, 2012, 04:37:19 PM »

"Enough" powder is really a question only you can answer. Obviously too much can be dangerous but it depends on what your planned use is. If it is shooting shot, then there is really no point is using more than will get the shot to the target reasonably. Shooting "over the mountain" presents danger (know where your shots will land) and is really somewhat lacking in satisfaction since you can't see where it lands.

If you're shooting blanks, you will probably want more powder but you won't see as much pressure either. 900 grains is about twice what I shoot but my gun is 30 mm.

The charge is traditionally ignited at the rear. Some experiments were done post-Civil War that determined that was the best place for maximum velocity.

rick1986 · « **Reply #12 on:** April 29, 2012, 11:36:08 AM »

Ok, I made the powder chamber 41/2" deep by 13/4" hole, clear full is 1800 grains of FFG Pyrodex. We will most likely back off from that for heavier projectiles. Thanks for all your help.

Double D · « **Reply #13 on:** April 29, 2012, 05:36:37 PM »

Why are you using pyrodex? Why are you using FFg Pyrodex. What is the black powder volume of 1800 grains of pyrodex.

There is no chart for Pyrodex because pyrodex doesn't work well in cannon applications. Pyrodex needs "pull" or resistance to work. In a 3 inch bore you would need a very heavy projectile or a patch to achieve the proper pull. . Both will drive pressure up often unsafely. As far as patching, because of the large diameter projectiles it will be extremely difficult to seat a projectile uniformly...

Also pyrodex is not used by weight it is used by volume. So how did you measure the pyrodex. What is its black powder equivalent.

If you are using that much powder why not just use blackpowder, it's cheaper and easier to use.

rick1986 · « **Reply #14 on:** May 06, 2012, 02:21:15 PM »

I am using Pyrodex because I am too dumb to know better. I thought that Pyrodex was just synthetic black powder that didn't corrode. How do I figure out how much black powder I need to use? And where can I get it in bulk? Or how do you guys do it?

Double D · « **Reply #15 on:** May 06, 2012, 02:53:01 PM »

Pyrodex is far more corrosive than blackpowder.

I have said in the past the black powder residue-fouling is not corrosive. That is not totally correct. Black powder residue is corrosive, but will not corrode on its own. It needs activated by moisture.

Pyrodex fouling is corrosive and does not need to be activated. It will corrode on its own. It really likes the zinc and will attack the zinc molecules found in some types of brass.

If you have not done it already visit the stickies at the top of the board and you will find lots of useful information, including how to find a safe load for your cannon.

rick1986 · « **Reply #16 on:** May 08, 2012, 05:20:53 PM »

Ok, I found lots of useful information. Is there any advantage to igniting the powder charge from the back with a 209 inline muzzleloader primer as opposed to a fuse?

Double D · « **Reply #17 on:** May 08, 2012, 05:25:04 PM »

Depends on how much your cannon weighs and how you are going to strike the primer.

Keep in mind you need to replicate pre 1899 cannon or antique ignition.

rick1986 · « **Reply #18 on:** May 12, 2012, 06:27:21 PM »

The chart from the stickys on top said the that I could shoot 6 oz of black powder and a 56 oz bullet for a 3" bore. That seems like an awful lot of powder. Does that seem right? The cannon wall is 3/4", and the powder chamber has a 3/4 wall, so 11/2 around the powder chamber.

GGaskill · « **Reply #19 on:** May 12, 2012, 06:42:39 PM »

On a chambered piece, use the chamber diameter for that chart. 6 oz would be for a 3" dia chamber, not the reduced chamber you have.

rick1986 · « **Reply #20 on:** May 20, 2012, 01:19:56 PM »

Why is that? For a better burn? My chamber is is 13/4" diameter. There is quite a bit of difference between the charges for a 3" bore and a
13/4" bore.

Double D · « **Reply #21 on:** May 20, 2012, 01:57:17 PM »

Quote from: rick1986 on May 20, 2012, 01:19:56 PM

Why is that? For a better burn? My chamber is is 13/4" diameter. There is quite a bit of difference between the charges for a 3" bore and a
13/4" bore.

With a chamber diameter of 1-3/4" the diameter of your barrel over the breach should be 5 1/2" to meet safety recommendations. For a three inch bore you need 9 inch diameter.

The reason a lot of people seem to use a howitzer chamber is they see it as a magic way to make a bigger bore cannon from a smaller piece steel. Kinda backward to my way of thinking. Howitzer chambers are harder to load than straight bores.

A difference between charges in 3 inch bore and 1 3/4 in bore? Seems reasonable to me.