What started out as a simple stomp-rocket style air cannon carnival game for my Son's school fair turned into another one of my overzealous project undertakings. The end result was a very fun and popular compressed air powered cannon and pirate ship with electronic explosion sounds.
Step 1: PVC Components
I started by test fitting the original cannon barrel PVC schedule 40 components. The cardboard tube is a Lava Lamp's packaging. The cannon balls are yellow foam practice golf balls from the local department store. I took one to the hardware store and found that it fit snugly inside a 1.5" PVC tube. The 'T' fitting has a 1" leg that I fit an additional reducer into it that accepted the knurled brass fitting for the rubber air supply tube.
Step 2: Miscellaneous Cannon Components
This shows the styrofoam ball (which will be cut in half) and PVC cap that will be used for the butt of the cannon. It also shows the cuts in the cardboard tube. There is one on each side, 180 degrees apart, that run from one end to about three inches from the other. This will allow an overlap so the cannon will have its tapered shape. There are also some miscellaneous other PVC pieces that will be used to adapt the brass ferruled fitting.
Step 3: Barrel, Pivot and Air Inlet
This is how the brass fitting for the air hose fits as well as where the 'T' has been drilled for the 3/4" diameter PVC pivot bar. I didn't have the right size paddle bit so I drilled a smaller hole and then carefully used a rat tail rasp to enlarge the hole. I made sure it was a tight fit so the PVC cement would adhere well and completely close the air chamber so there are no leaks. It took a few coats and patience to make sure it was air tight.
Step 4: Barrel Fit Into Tube
I pulled the cardboard tube open where I had cut it so the pivot bar would slip in. I trimmed the cardboard to allow the bar to fit nicely. This end of the PVC has been piped down to to size to accept the end cap.
Step 5: Barrel Detailing in Prepration for Covering
I used masking tape to attach some small diameter rubber tubing to form some reinforcing ridge detail. The original packaging for the lava lamp had some styrofoam keepers that I cut a hole in and glued inside the cardboard tube to keep the PVC barrel centered. The black plastic end cap was then put on, the styrofoam ball was cut in half and a hole was bored in the center so it would fit over the protruding portion of the PVC barrel.
Step 6: Covering
Here's the first piece of plaster fabric (such as Rigid Wrap, found at most craft supply stores) draped on the cannon. It took some work to get it tight along the edges of the rubber tubing so it didn't bulge. I then worked the plaster smooth. Each piece was overlapped in different directions. I made sure to smooth things out so the pattern of the fabric did not show through too much.
Step 7: Completed Covering
The fully covered and smoothed out cannon. Notice the butt end with the PVC cap protruding. This is where the kids will hold the cannon when aiming it. This way all of the pressure is transferred through the PVC an not on the cardboard or plaster fabric. Once it is completely dry, it was spray painted semi-gloss black.
Step 8: Drilling the Saddle
An 8" length of 2x4 was used for the saddle on the carriage. A 1" hole was bored in the center. Two 3/8" holes were drilled as shown in the picture. Then the piece was cut lengthwise through the center hole. The 3/8" holes will be used to fasten the carriage pieces together using dowels and wood glue.
Step 9: Carriage Sides
Here are the two sides of the carriage pinned with the dowels and glue. I clamped them down tight and let them dry over night.
Step 10: Nearly Comleted Carriage
A wood rasp was used to weather the edges. A 'tie-down' ring was fashioned out of a ring from the craft store and a strap used for fastening copper water pipes to rafters. It was snipped in half and bent using pliers. The wheels halves were cut from 1"x4" pine board and glued/clamped over night. The axles are 1" PVC pipe painted black. The wheels where held to the axles by drywall screws - you can see them in this picture.
Step 11: Hub Caps
Hub caps where cut from the 1" pine board and notched/weathered using a wood rasp. They were glued on using wood glue to cover the axles.
Step 12: Test Firing and Adjustments
After the first test firings it was determined that using the full length of the cannon provided too large an air chamber. The cannon ball only plopped about six feet. I picked up a few more parts from the hardware store and tried firing with a smaller camber. The bright white PVC with the black handle is part of an irrigation system that is hooked into an 8" piece of PVC. You can see the cannon ball, a yellow foam practice golf ball, stuck into the other end. This proved to be much better. Still only about 20 feet with a good stomp on the bellows (the black oval under the PVC)
Step 13: Chamber Reducer
This shows one end of the irrigation valve that I cut off. It was already threaded to accept the 3/4" brass ferruled fitting. I used some pipe tape to make sure the connection was air tight. The rubber hose was fed in through the location where the original brass fitting was at the bottom of the 'T'. It was fastened with a hose clamp since it will be glued in permanently. The reducer was then glued into the barrel about 4" from the end.
Step 14: Installed Chamber Reducer
The business end of the cannon with the new air camber installed and glued. It is in about 4" or so from the end.
Step 15: Mounting the Cannon to the Carriage
More copper pipe straps were modified to create a fairly tight pivot to keep the muzzle of the cannon from dropping down - since it is a bit heavier in the front. I used brass screws to keep things looking nice. Also, I drilled a hole into each pivot bar to accept a 10 penny nail to keep the cannon from sliding left to right. You can see the head of the nail next to the inner strap - it is painted black also.
Step 16: Target Ship
This is the target (the ship, not Cole). It was simply created using cardboard and hot glue. The detail around the deck is 3/16" dowel rods. We have created three battle damage holes which will be the goal to get a large prize.
We covered the hull and decking with shelf lining paper. A black Sharpie pen was used to 'burn' the damage to the hull.
The final picture shows the ship after being painted and ready for the rigging. The 'crows' nest is a wood napkin ring. It will have a floor made from cardboard and will be glued to the mast.
Step 17: Main Sail
These pictures show how the main sail was cut from a thick muslin cloth, painted to look weathered and to have the ominous skull and cross bones. The final picture shows the black string used to tie the horizontal 'yards' to the mast and to attach the sail. Hot glue was used to keep the knots from unravelling. Also shown is the finished crows nest.
Step 18: "Davey Jones' Locker"
"Davey Jones' Locker" was built out of the same pine board. It measures 8" long by 6" wide and 6" inches tall. This will be used to hide the blow gun firing mechanism. More details will be added to create the look of a chest. We will use a small wooden ball on the top that will have a dowel rod fastened to the bottom. The dowel will go through a hole in the lid. When the ball is pressed down the air gun trigger will be pushed to fire the cannon. The lines and detail were created using a carpet knife.
Step 19: Trigger Mechanism
These pictures show the schematic, blow-gun cradle, installed blow-gun with ball/dowel trigger, the painted and detailed "Davey Jones' Locker" trigger and finally the scuba tank hooked up.
Step 20: Explosion
A co-worker's brother built an electronic circuit with three sensor beams to place within the ship's hull. When a ball breaks the beam the unit emits an explosion sound that is delivered through a pair of computer speakers. This was an awesome touch!
The sensors were installed in the hull. Each of the wood sensor pucks had to be cut in half to fit the larger holes. I painted the exposed ares of the wood for the sensor pucks black to hide them a bit. Some of the inside was also painted black so the cardboard didn't stick out like a sore thumb.
Step 21: Carnival Day Videos
The first of these two very short videos show how the firing worked by simply 'slapping' the trigger with the palm of your hand. The foam ball was pushed into the muzzle until it was flush with the end.
The second shows the ball bouncing into one of the holes triggering the explosion (it is hard to hear on the video). We also had made some flat targets out of cardboard and foam posterboard. I printed pictures of pirates and glued them to the targets.
It was a huge hit at the carnival and I'm expected to bring it back every year.
Thank you for allowing me to share this.