4" caliber 'Product Launcher' ABS Cannon

Because the prototypes I wanted to shoot were just over three inches wide, I had to go up to a larger size of ABS pipe of four inches (102 mm). But this presented a problem: No amount of wadding could fill the space between the unit and the canon's caliber.

The solution was to make some 4" wooden plugs. I made the plugs precise enough that with one end of the barrel closed, when I dropped the plug in, it took a good 20 seconds for the plug to fall down the barrel. I also cut a groove around the circumference of the plug to squish soft material into to act like a piston ring.

This picture shows two of the plugs I made. The plug with the blue cloth attached has a slot to help hold the BlackBerry. The blue cloth is intended as a sort of drag chute to slow down the plug once it leaves the barrel and separates from the BlackBerry. It should also make it easier to find in the grass. The idea is to fire the device a long way, but I don't want the plug to fly off into oblivion. Behind the plugs is the back end of the cannon, with the spark plug facing the camera. You can also see the fuelling valve at the end of the barrel. The wooden block around the valve is to catch the recoil. To the left of that is a bunch of AA batteries wired in series. I used these to power the ignition coil.

When I first tested this cannon, I used propane and oxygen. The shots were loud, but I was a bit disappointed, because I expected it to be unbelievably loud. To push the plug out of the barrel takes a 5:1 expansion of the gas, and that was probably all the expansion I was getting with that fuel. For the actual "launching" event, with lots of co-workers there, I used "BernzOmatic MPS gas". (I should add that this event was neither official nor sanctioned by RIM) The bottle says it's "Methylacetylene Propadiene, stabilized". It also says "Burns Hotter than Propane for Welding, Brazing and Soldering". I mixed it with oxygen, of course. What a difference that made! It made a good bang! The muzzle flashes were also quite impressive.

We launched some BlackBerries into the air, but we had a hard time retrieving them - all we could find were some plastic parts that broke off early. The actual devices were out in the field somewhere. But thanks to the drag chute on the plug, we were able to locate and reuse that each time.

When shooting into the air, most of the kinetic energy is eventually lost to drag. So I figuresd it would be much better to shoot the BlackBerry at a target at close range. I bought a 1" thick steel plate to use as a target. The above photo shows the cannon an instant after firing. You can see the cannon in mid-air from recoil. The pieces of wood on the left were there to absorb some of the recoil. The mess on the right is the target area. Towards the top of the photo, you can see the plug (what's left) ricocheting off, while all the dust is probably parts of the device from the impact.

The device itself accordion folded in several places from the impact. Behind the green patio table "blast shield" is Ron Harding, with his camera (also protected) taking pictures at close range.

I invited some people from work to the event. Jack (whose property we used) had kids, and there was also a kid's birthday party at a neighbour's and they came to check it out. So it made for lots of spectators. It was possible to herd all the kids into the garage (in the background) for the actual fuelling and firing. But between shots, it seemed like there were kids running around everywhere. Not that there was anything to blow up, but you never know.

My previous cannon lasted for many firings, and I figured because of it's simple construction, this cannon should last a long time too. But I hadn't used MPS gas before.

I noticed the 2" screw plug I had at the breech had somehow come out partway after some of the firings. On later examination of the videos, I could see quite a progressively larger flame coming out from the plug, even though I re-tightened it every time. Somehow, the pressure was enough to get it to skip threads. The only thing that kept it from coming all the way out was that it hit the wooden bracket on the back of the cannon.

Still, the impact was enough to completely destroy the device - more effectively than firing a wooden plug at it. The deceleration at impact alone was enough to rip all the components off the circuit boards.

In addition to firing the cannon, Kent Nickerson also brought some model rockets which he fired off. After this wanton destruction, we were all feeling more manly and satisfied. We subsequently had a nice BBQ courtesy of Jack's wife. We also reviewed the video footage just taken. Food and entertainment, who could ask for more?

As we finished up, I decided to shoot the empty oxygen cylinder (one cylinder only has enough gas for about ten shots). I used a somewhat damaged plug, which took a bit of force to ram down the barrel. The shot itself was very disappointing - the bottle must have flown no more than 20 meters. But on close examination, the barrel had a big crack along its length.

There was still room for improvement with this design, such as fixing the leaking plug issue. The next BlackBerry product I "launched" was just under 3" wide, so my next cannon used a 3" barrel, with a 4" reinforced combustion chamber.

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