Carbide Cannon Success Story
It came right down to the wire, too, for getting carbide. I purchased "Miner's Grade" carbide, which then had to be crushed. I was able to locate and purchase a reasonably inexpensive 1-ton arbor press (I think it was your site that suggested it) that worked pretty well for crushing the larger "rocks." It took several hours to crush about 2/3 of a 2# can. After spending hours crushing the carbide, I'm seriously thinking about buying the tubes of the powdered carbide (Bangsite).
Finally mounting the finished cannon to the carriage was a great moment. Several friends had been in on the project, since my wood working skills are minimal, at best, so telephone calls went out across the neighborhood.
Time for the first firing...
My wife, youngest son, and neighbor were in attendance. I had the crushed carbide...I had a small measuring spoon (1 tsp)...I had a small funnel (a cake decorating tip)...Water had been poured down the barrel to fill the base of the PVC "T"...I had my ignition source (a small butane lighter). Deep breath... Kneeling beside the black beauty, I scooped out about 1/2 tsp of crushed carbide, lined up the funnel, and poured...only to find that the carbide was a little too large for the funnel. Some finer grains did make it into the chamber, though. With everyone watching, and not wanting to make the first shot a dud, I decided to wait about 10 seconds, and try the shot. Sad to say, it was a dud - just a hollow popping sound, similar to what you might make popping a finger out of a soda bottle. Hmmm...
Using my custom-made (1/2" PVC and a tin can) ramrod, I vented the barrel... This was going to work. I was sweating...sure hope a drop of sweat doesn't fall in the carbide! OK...I'm ready...I scooped out only the finest grains of carbide from the bottom of the jar. The ammo poured smoothly into the chamber. Now I had to wait...but not too long! Holding my finger over the touchhole, I counted off about 5 - 7 seconds. Putting the lighter tip to the touch hole I offered a small prayer for success - this had been a three week project (I'm real slow with wood), and it just had to work...the next day was the 4th of July!
I pressed the trigger on the lighter... once... no flame... twice... still no flame... was there fuel in the lighter? Third time's a cha...KAA---BOOOOM!
Not only was it a hideously loud and thunderous boom (the word "blast" does a better job of conjuring the right image), but it also set off the burglar alarm in two cars on my street (one of them was my own). I had the vague impression of a muzzle flash about the size of a cantaloupe. The patch of tall daisies that were (and still are) standing about 15 feet away had visibly moved with the concussion, and were now swaying back and forth in what was perfectly calm air. Within moments, the echo made it back to me - this was more than just a winner. I looked up at my family and neighbor, and couldn't speak. I could only mouth the words "Holy Sh*t!".
About a minute later, I received a very stern warning from a 7-year old neighbor boy, that at the sound of the blast, one of his three dogs had wedged itself into the closet and had to be dragged out. I wanted to offer to use the dog as wadding for the next shot, but felt it best to keep the peace. There were no more shots that night.
Needless to say, there were many shots on the 4th. I had people coming from 4 blocks away wanting to know where the house was that had the cannon. It was the hit of the party.
Putting flour down the barrel, as suggested by the plans, didn't make much of a "smoke" cloud, though. Typically, the flour only burned, which made for a warmer blast, with a swirling fireball, instead of a brief, almost instantaneous, flash. The flour also contributed to a wonderful smell of burnt toast that lingered around the area when there was no breeze. I was a little concerned about burning flour that might linger in the barrel, so I discontinued the experimentation. I'm going to have to look around a little more for some material that won't burn...maybe baking soda.
After sunset, the shots were nothing short of spectacular. After overcoming the obstacle of not being able to see what I was doing (flashlights in the hands of friends work wonders), I was shocked to find that the cantaloupe-sized muzzle flash (in broad daylight) had grown to the size of a healthy beach ball, and was bright enough to light up my entire yard. The fireworks that I had purchased for the evening lasted quite a bit longer, since we spent lots of time admiring the beast, talking about could have been done with the design, and (lastly) reflecting on the manly KA-BANG made by each shot.
With no small measure of regret, I had to roll the monster back into the garage at 11pm. A small tear welled up in my eye as I turned out the lights... another day would come, though.
I'm sure that my new, as yet un-named, cannon will be hauled out for many a family function down through the years.
Now that the story is complete, I thought I'd give a couple of construction notes:
1) Large PVC fittings aren't cheap. The article on the web site says less than $100, but that was in 1976 dollars. The plastic fittings and short lengths of pipe were $111. Add to that about $12 for a 2x12x10, $8 for a 1/4 sheet of 3/4" plywood, $8 for a quart of bonding primer, $8 for black paint, 1" dowel for axels was about $2.50, 1/4" dowel for the axel pins was about $1.00, miscellaneous screws and other minor hardware was another $10. Add another couple of bucks for the anti-skid sand that I forgot to add to the paint.
2) I had a cabinet shop cut the 7" circles for the wheels. Unfortunately, the green Douglas Fir wanted to crack as it dried, so I had to purchase mending plates and additional screws to make it so the wheels wouldn't break apart. Cutting the wheels: $10, mending plates and screws: $5
3) I chose to make a guide for the elevation jig to slide back and forth on, instead of it just sliding free inside the carriage. More screws and the metal for the guide rails: $5.00
4) $8 for the beer given as a "thank you" to my buddy that donated his table saw, radial arm saw, and drill press to cut/bore the 2x and the plywood parts.
5) 1-ton arbor press - $35 at Harbor Freight (http://www.harborfreight.com). Luckily, there was a retail store locally, otherwise I would have been forced into coming up with a plan "B".
5) I used "Gorilla Glue" in the "glue-and-screw" process of putting the carriage together. This is incredible stuff that will cause plywood to delaminate before the glue bond breaks. The same guy that helped me cut the wood donated the bottle of glue. If I had to buy it: $20!!
6) I decided that I didn't need the headache of making wooden "uppers" for the trunion bearings. Instead I used 3/4" copper couplings over the 1/2" PVC trunions (a perfect fit), held in place by galvanized pipe straps. If I had been able to find copper straps, I would have used them, but time was short. If/When I find them, I can easily swap them out.
7) If you can avoid it, never use a hand-held drill to make the holes for the trunion pins. Get two friends to hold the cannon...use an extremely sharp bit...and use a drill press. This is experience talking.
8) 1/2" PVC trunion pins require 13/16" holes. If the drill bit is sharp, you shouldn't have to dremel out the holes. My dremel got a workout on this whole project.
9) In order to spare the paint around the 1/4" charge/touch hole, I used 1/4" copper tubing to line it. After cutting about 1-1/4" of tubing, I positioned it in the hole and used a nail set to flare the end that was outside of the PVC. Then I used a small ball-peen (sp?) hammer to gently complete the flare so that it was flat against the outer surface of the pipe. If I had to do it over again, I would have done this AFTER painting. I then took a couple of 1/4" galvanized washers and stacked them over the end of the copper tubing inside the pipe. Gorilla glue...washer...glue...washer...glue...washer. After allowing 24 hours for the Gorilla glue to dry, nothing in this world is going to knock the tubing loose short of drilling it out.
10) I used some epoxy to make "welds" around where the trunion pins meet the outside of the combustion chamber. They look just like real (painted) welds after being sanded down. Because the holes where the trunions were inserted were so tight, I was unable to use PVC glue to lock them in place. Thus, I wanted to ensure a lasting connection.
11) I was able to pound the trunions into their holes far enough to allow for PVC caps to be inserted inside to further ensure that the pins wouldn't one day decide to come shooting off to the side of the cannon.
12) Modern (and maybe 1976 vintage) PVC fittings of this size have hollow cavities. When I drilled the holes for the trunion pins, I did not use anything (like epoxy) seal the PVC in these cavities. While the fit is quite tight (there is no daylight visible), some high-pressure out-gassing could be felt by spectators. On the other hand, though, this could have been the shock wave - the detonation is that strong.
13) Lastly, this field piece is large enough to generate some recoil, even though the barrel is completely open. On freshly cut grass, I found that each shot would move the carriage backward about an inch. On a smooth surface "chocks" for the wheels might be a good idea.
And that's my story. She's a beauty, she's my baby, and I'm proud of her.
Thanks for the inspiration.
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