Carbide Pirate Cannon

At the suggestion of another member, I've created this thread.

If you've looked at my signature, you've likely seen the youtube link for the carbide cannon I made a few years back for my kids. (Honest...for my kids. I wouldn't lie about that!). If you search "Carbide Pirate Cannon" on youtube, you'll find it.

This will involve several postings, as I'm essentially copy/pasting from my original Word document I made to explain how I made it. I'll also be posting several pictures. So if you're reading this and it looks like I'm not quite done...hang on, because the next posting will be up in a few minutes.


And now...THE CANNON!

I have always wanted to build a carbide cannon. However, for one reason or another, I never actually got around to doing it…until recently.

In 2012 I finally sat down and did some research on the subject. Making a simple carbide cannon is easy, but I wanted something special. I wanted something that not only was fun to actually use, but was also fun to look at and would, perhaps, spark some interest in some real history concerning cannons.

All the homemade carbide cannons I found online, even the “good” ones, invariably ended up looking like a bunch of PVC pipe glued together and perhaps painted black. Really fun to make and play with, I’m sure, but in the end they all pretty much looked exactly like what they were made of: PVC pipe. So I decide my project would be guided by two principles:

1. No “redneck” cannon: the cannon couldn’t look like a bunch of PVC pipe glued together.

2. Following the general philosophy that “bigger is better” with respect to sound effects, the cannon couldn’t be small if I wanted it to actually sound like a cannon and not a glorified firecracker.

After doing some research, I decided I wanted to make a replica of a 24-pounder off the USS Constitution, the famous 44 gun frigate launched in 1797 and still sailing today as the world’s oldest active naval vessel. This particular cannon design I’ve always been fond of, having made one about 8 inches long out of steel on a metal lathe in shop class during junior high school some 35 years or so ago.

The link I would use for the majority of the scale work I would be doing came from this image, which is an eighteenth century drawing of a typical naval gun and its truck carriage, which the 24-pounder is modeled after:

The original 24-pounder is approximately 9 ½ feet long and, sitting in its carriage, weighed in at about 6,000 pounds. Though I was all for “bigger is better” on this project, 9 ½ feet presented me with some serious transportation difficulties. I wanted something between 5 and 6 feet in length. In the drawing on the previous page, the image on the website measured just under 7 inches in length from muzzle to cascabel. For simplicity, scaling the drawing up by a factor of 10 would produce a cannon in the size range I was looking for. The math thus worked out quite simple, since multiplying by 10 is so easy.

I started gathering the materials I would need a little bit at a time starting about a year ago. All the PVC parts necessary, the PVC cement, foam insulation for the body, and so forth. The goal was to have everything finished by July 4, 2012 so that it could be taken to my wife’s aunt and uncle’s place on the lake, where we go nearly every year to celebrate Independence Day. One of my wife’s cousins always brings a TON of fireworks and puts on an awesome fireworks show when dusk comes. This would be something that our kids could actually operate before, and even during, the fireworks show. (NOTE: This particular cousin has really been getting on my wife’s nerves this last year, so upstaging him should earn me some good-will credit…)

When everything was gathered up, I finally let the kids in on the project…I would be building a cannon for the 4th of July. But they couldn’t fire the cannon unless they were dressed like a pirate and had pirate names. I told them all they had to have was an eye patch or something, but Daddy’s Little Troublemaker immediately decided I had to take her out shopping for a full set of pirate clothes. I wonder which side of the family she got the “outlandish project” gene from?

So in May I finally got started. I glued the PVC pipe together to form the “core” of the cannon. This core is constructed from 6 x 6 x 4 tee, a 6 x 4 adapter, a 4 x 3 coupling, and a 3 inch diameter pipe. Then I framed up a simple 2 x 4 jig I would use to hold the cannon while I did the body work on it. The body work would consist of layering 2 inch thick blocks of foam on the PVC core which I would then cut/carve using a scale pattern I made from the figure on the previous page. The pattern was cut from two 1 x 6 boards and mounted on the sides of the jig and used to guide a hot wire to progressively slice layers of foam away until the body of the cannon was cut out.

Then the foam was rough sanded afterwards using some 80 grit sandpaper to remove the final hot wire cutting marks and make the canon barrel round. Some hand carving was required around the 4 inch cleanout plug on the bottom of the tee at the breech. A line was drawn down the length of the bottom of the cannon, and each layer of foam was sequentially numbered. This was to allow me to remove the layers of foam for gluing and to install the trunnions on the barrel. The trunnions are the “pivot points” of the cannon…the part which actually rests on the carriage and allows the cannon to be angled up or down as desired.

For ease of construction, the trunnions were constructed using 1 1/2 inch PVC pipe. True to scale would have required trunnions about the same diameter as the barrel, but cutting them through with the accuracy I needed and the equipment I had would have been too difficult and time consuming. The trunnions were cut from a 24 inch length of pipe using a hole saw the same diameter as the outside diameter of the PVC barrel. Then the curved ends were plugged with a center drilled PVC piece epoxied in place so that they could be bolted to the barrel. To prevent blocking the barrel internally, round headed bolts were used, inserted into their holes from the inside of the barrel. The trunnions were then cemented in place and clamped with the bolts, doubly ensuring they will be solidly mounted.

OK, now to catch up with some pictures.

Below is a picture of the PVC "core" about which the foam body would be built. You can see the "jig" I made for it and how it would fit in it. If you look closely at sides of the jig in the bottom pictures, you'll see the patterns I screwed to the sides which guided the hot wire as I carved the shape of the cannon out of the foam.

Unfortunately, I didn't take any pictures of the fabrication and attachment of the trunions, but you can see them right after I attached them in this picture.

Trust me when I say they are NOT coming loose!

At this point, the cannon body was primed with a coat of KILZ latex, with some drywall mud mixed in to thicken it up and help fill in cracks and crevices inherent with the layered foam. This primer coat is required to seal the cannon to allow it to be spray painted later without the spray paint literally dissolving the foam body. The KILZ was tinted grey just so I wouldn’t have to deal with a white primer during later painting, or for minor scuffs over time.

After the first coat of KILZ, I used some spackling compound to fill in minor gaps and deficiencies in the body of the cannon, then applied a second coat of KILZ over that. No attempt was made at “perfection” during this, because actual cast cannons during this period of time did not have a smooth, polished appearance. All I did was fill in gaps between layers and eliminate or soften the appearances of some minor defects made while cutting the foam with the hot wire.

The next major piece of work involved the carriage. Unfortunately for me, the Naval Base I’m near no longer has a wood shop. Neither, it turns out, do any of the other military installations in the area. Enter my oldest brother and his wood shop! It turns out that he had all the lumber necessary to make the carriage in the wood rack in his shop. The sides and the cross members on the bottom would be made from 2 x 10 laminate beams we removed from his house on a previous project a few years ago. The wheels and axel blocks were made from Ash. And the axels were made from some mahogany round stock he had left over from another project he had worked on some few years previously. All I needed was a weekend, and some miscellaneous hardware (bolts, nuts, washers, eyebolts) and I would have the carriage put together.

Then the wood was stained dark walnut to bring out the grain and coated with a couple coats of satin finish polyurethane sprayed on to seal the wood. A “natural wood” look without a cabinet level finish was desired, so no attempt was made to apply successive layers of polyurethane for that type of smooth finish.

The carriage was also designed to be disassembled so that it could be easily transported in my car. However, it turned out that the finished carriage will sit completely in the trunk of my car if I simply unbolt the axel blocks and remove the axels. This makes transportation and assembly much easier.

The hardware would later be painted black and the trunnion clamps have yet to be fabricated. The trunnion clamps, to be realistic, need to be hinged with an eye bolt on the rear of the clamp. The front was held in place with a peg and eye bolt on the real thing. I may fabricate a temporary set of clamps out of 1/16 inch thick aluminum, for ease of work, until I can get around to the real deal later.

OK, now to catch up on the carriage pictures:

The first picture is the "raw" carriage. It's partially assembled and unstained/finished. I hadn't installed the axel mounting blocks at this point.

So, I broke the carriage down, fabricated my axel mounting blocks, then stained everything a walnut color (because I like walnut stain) and sprayed everything down with three coats of satin finish polyurethane as a moisture barrier. Partially assembled, it looked like the bottom picture.

At this point in time, I could use the carriage as a cradle to hold the cannon while I worked on the last major piece of the cannon: the breech.

The breech of the cannon is a 6 inch cleanout plug with two gas grill igniters installed. The igniters are wired to a battery powered push button ignition source, which produces a reliable, high quality spark. This is the heart of the firing mechanism for the cannon. A foam “endcap” needed to be carved, which involved making another pattern. This would be glued to the end of the cannon, covering the igniters and wiring. And, finally, a wooden ball would be bolted on to form the cascabel. More body work, sealing with KILZ, and this was done.

For the vent (the priming/firing hole), I used a 3/8 inch brass tube with the end swaged, or “flared” out, to hold it in place. It is also firmly installed using epoxy.

The trunnions were notched on the bottom to accept dowel rods used as alignment pins, in order to prevent damage to the body of the cannon while sitting in the carriage. This keeps the cannon centered in the carriage, preventing it from sliding to one side or the other and rubbing against the hardware. The trunnions were then cut to length and capped to give them a solid appearance, instead of that of a pipe.

Finally, the excess PVC pipe was cut off flush with the muzzle. The muzzle was primed with KILZ, then smoothed over with spackling compound. Again, some minor attention was paid to smooth out defects, but perfection was not the goal.

The cannon, at last, was ready for painting!

More pics to catch up.

The top two you can see the cleanout plug with the gas grill igniters installed.

The next two you can see the brass vent. The position of this vent is such that it's above the 4 inch cleanout plug of the 6X6X4 Tee which makes up the breech. (You can see this in the very first picture of the PVC core above). This is not actually the "correct" position of the vent on the real cannon, as it lies further back towards the rear of the cannon. But I'm the engineer and I get poetic license to make this how I wish, and it has to be positioned this way so that it's above what will form the water reservoir essential to how the carbide cannon will work. (More on that later.)

Here is the work putting the breech endcap on:

And here's the cannon after I've finished all the "artwork" on it, primed and ready to put the final coat of paint on (with some muzzle work). The carriage is almost complete (it doesn't have the pegs installed yet to hold the wheels on).

Painting was accomplished by driving a 2X4 into the ground, cutting it down so the 3" PVC barrel would fit over it, and then standing the whole barrel up on the 2X4 so I could shoot a couple coats of black spray paint on it. When it was dry, I laid the cannon back onto the carriage and shot a coat on the face of the muzzle.

So, now I have a carbide cannon which actually LOOKS like a cannon and not a bunch of PVC pipe glued together and painted.

Final specifications:

Cannon length: 69 inches long, muzzle to cascabel

Cannon weight: 23 pounds

Carriage length: 40 inches long

Carriage weight: 79 pounds.

Total weight: 102 pounds

All that remained now was to actually test fire it. Which brings up the question of how, exactly, does this thing work?

HOW IT WORKS

I said earlier that this is a calcium carbide cannon. Three things are needed to make this work: calcium carbide, water, and a spark/flame.

The cannon is mounted so that the 4 inch cleanout plug is on the bottom of the breech. With the plug installed, it is filled with water…a cup or two is plenty. This cleanout plug lies directly under the vent at the top of the barrel.

When you are ready to fire the cannon, you pour a small amount of calcium carbide powder through the vent. The calcium carbide will react with the water to form acetylene gas. After waiting about 10 seconds to allow the gas to form and mix with the air in the firing chamber, the button is pushed to ignite the gas, producing, in the immortal words of Marvin the Martin, “An Earth shattering KA-BOOM!”

All that’s required to fire the cannon again is to air the barrel out with fresh air and add some more calcium carbide. This is done using a ramrod, which consists of a paint brush roller sized to fit the barrel mounted on a PVC pipe (painted wood-brown, to avoid the “redneck” look of PVC). The ramrod is pushed down the barrel, forcing bad air out the handle. When it’s pulled out, fresh air is drawn back down the barrel. Kinda lends some authenticity to this, huh?

Periodically, the water needs to be changed out. After a few test fires, I decided it was unwieldy, and messy, to do this the original way it was designed: remove the 4 inch cleanout plug and drain the water that way. It also seriously detracted from the fun of shooting the cannon. So I installed a small valve in the cleanout plug which accepts a ¼ inch plastic tube. Just open the valve, let the water drain out, shut the valve, and add more water to the cannon.

The beauty of using calcium carbide instead of an explosive like gunpowder is that you cannot over charge the cannon and produce chamber pressures high enough to blow the cannon apart. If you use too little calcium carbide, you get a dud because there isn’t enough gas to ignite properly. If you use too much calcium carbide, the gas displaces too much air and won’t ignite at all…producing another dud.

Some experimentation determined that, for this size of cannon, ¼ teaspoon of calcium carbide and a 10 second wait before ignition produces a reliable blast. A rounded ½ teaspoon produces a truly awesome blast and definitely requires hearing protection, even while standing behind the cannon. (I recommend hearing protection at all times, however.) Minor deviations from this will also work adequately, but I haven’t gone above a rounded ½ teaspoon. Further increases in the amount of calcium carbide aren’t likely to produce any appreciable benefits anyway.

If the igniters fail (dead battery, broken wire, etc.), the cannon can still be set off by means of a spark or lighter applied at the vent. This is perfectly safe.

FREQUENTLY ASKED QUESTIONS:

1. Is this a spud gun? I did not design this to be a spud gun. I designed it to be a really, really cool looking noise maker. Schedule 40 PVC is plenty strong enough to have made this a spud gun with a couple possible exceptions that I would have had to engineer for and test. One is the fact that the breech is 6 inches in diameter with a cleanout plug that's drilled for igniters and cascabel. That's a rather huge surface area for pressures to act against in something like a spud gun, where the barrel is tightly blocked with a potato. Also, I chose to drill mounting holes in the barrel for the trunnions. These are untested weaknesses that I have no interest in testing by jamming a tightly fitting potato as a blockage in the barrel. Had I taken the time to extensively test this prior to construction, perhaps this would be a spud gun. But I have no intention to either wreck something I’ve spend some weeks on building, or to hurt anybody who may use it.

2. Will this shoot anything? As I said above, this is designed to be a really, really cool looking noise maker. However, as built, the schedule 40 PVC will easily hold up to launching something fairly light weight which does not tightly block the barrel. Like what? Well, it turns out Walmart has these oversized tennis balls that PERFECTLY fit the 3 inch barrel. This cannon will happily launch one of those buggers about 100 yards at max barrel elevation in the carriage. (After a half dozen or so firings, they're not quite so "fuzzy" any more...)

3. What gave you the idea to build something like this? No one thing in particular. I was somewhat pyromaniacally inspired as a child, so I’ve always wanted to build something like this. I’ve always loved cannons like the 24 pounder this is modeled after, as well. A variety of things went into this, many stemming from childhood…and having children of my own, as well. Sea shanties and things piraty (is that a word?) have been a pastime. And, of course, the Pirates of the Caribbean fad, of which my family is no stranger to.

4. How much did this cost? Honestly, I haven’t sat down to figure this out yet. I bought nearly all I needed to build this over the course of a year…a piece here and a piece there. So it’s not been a real financial burden. I will, some day, put together a list of all the material necessary. It took me about 3 ½ weeks to build, once I started. At a minimum, I'd say you're looking at over $500 in material, and remember...I got the wood from my brother's wood shop.

5. Would you make one for someone else? Yes, but only on a case-by-case basis. This takes time, and some parts require tools I don’t have myself (yet), so it’s a little inconvenient for me because of this. If I had the time, and the person who wanted one bought all the necessary materials up front to demonstrate their willingness to invest in the expense, then I likely would do so for a set price, based on my experience at how long it takes to do the work.

6. Where do you get calcium carbide? I buy it in powdered form as “Bangsite”, from the following web site:

http://www.bigbangcannons.com/products.aspx?c=10

This site sells carbide cannons of their own, along with all the material needed to operate them. This company has been around for a hundred years, and the calcium carbide cannon itself for a wee bit longer. (NOTE: Mine is bigger than anything they have. Bwahahahaha!)

7. Does this really fit in your car? Heh! Yes, it does! The carriage fits fully assembled, sans the axels, in my trunk and the cannon itself I lay on the front, passenger seat of my car after reclining it into my back seat. Yes, there IS a funny story where I was pulled over in the wee hours of the morning by a Virginia State Trooper and had to answer the question: “Do you have any weapons in the vehicle?” How could I answer that with a straight face?



8. Is it loud? “Loud” doesn’t really do it justice. Let’s just say that everybody on the block will know it when I light this baby off…and the next block over...and the block over from that…and the block over from that…

9. Is it legal? Depends on your city/state laws and ordinances. You’ll have to look this up yourself. Some places may require a permit. I read that Pennsylvania only allows carbide cannons which use 1/10 ounce or less of calcium carbide. Mine is well under that limit. States like South Carolina and Tennessee are not nearly so strict as others.

10. Was it difficult to build? Not really. Nothing about this was “difficult”. A person with basic skills in math (ratios) and basic wood working skills can do this. Some other minor skills are easily learned, if you’ve never done PVC work and such. But it DOES require patience.

11. What will you do with this? Well, it was originally meant to be for use on Independence Day. However, any event which may require either a really cool looking cannon and/or a really loud noise is perfectly suitable. New Years Eve, parades, National Talk Like a Pirate Day (September 19th), contests, plays, or getting revenge on your neighbor who just WON’T turn that d*mn stereo down. I suppose if you own an SUV or pick-up, you could use it on tailgaters. A Halloween decoration would be neat. Perhaps there will be an opportunity to enter it into a contest or something.

12. Do you have a video of this? Yes. You can find it on a youtube search for “Carbide Pirate Cannon, posted by RetiredUSNChief. The link is:

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CapnMac said:

Now, an option on the carriage is to paint it either red or green.
But, such a cool build not matter how you shake it.

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Yeah, the period cannon had painted carriages, not stained/finished. I did it this way because I like to see the wood grain!

ApacheCoTodd said:

What a neat project. The finished item is very impressive. Do you have a video of its firing?

Todd.

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Yes...the video is in post #18, and is also in my signature line right after "I'm the guy with a cannon, too".

JShirley said:

That is really neat. Thank you for taking the time to share it with us.

I'd like to make a black powder can mortar, at some point. I used to be a mortarman, so I think a 67mm mortar should be fairly easy to handle (just like a real 60mm mortar).

John

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Not long after completing the cannon project, I thought about making a pair of mortars as launchers for the "big fireworks". When I got sent to Charleston, SC for work, I immediately went to the Battery with tape measure and notebook in hand.

I never got around to making them, and Lord knows were my notes got to since. But my vision was to make a scale pair that I could put "sleeves" into the barrels of in order to accommodate different sizes of fireworks mortar rounds.

It would look radically cool to be launching fireworks that way!