This is sometimes referred to as a tennis ball launcher or even a Polish cannon.
Before we get going with the instructions, we must warn you that if you build this cannon correctly,
and you use it correctly, IT CAN INJUR YOU!
Let us repeat that.
THIS CANNON, WHEN USED CORRECTLY, CAN INJUR YOU!
Having said that, who knows what it will do if you don't build it correctly or if
you don't use it correctly?
Use common sense! Don't do this if you're not an adult. Treat the completed cannon
as if it were a gun. Always point it in a safe direction.
Be responsible. Don't be an idiot.
The total dimensions of the cannon are 33 1/8" tall, and 2 5/8" diameter.
Now, let's start with parts list:
- 6 tin cans, 2 5/8" diameter, 5½" tall (Fig. #1)
- 1 tin can, 2 5/8" diameter, 3 1/8" tall
- can opener (Fig. #2)
- can opener (Fig. #3)
- duct tape (Fig. #4)
- Ronsonol lighter fluid (Fig. #5)
- tennis ball (Fig. #6)
- lighter or matches (Fig. #7)
First, a few things about the above parts. Getting the right tin cans is the hardest part.
The key factor is that the diameter must be 2 5/8".
We just went to our local grocery store with a tape measure.
We measured soup cans, tomato cans, vegetable cans, etc.
Most cans you'll see have a 3" diameter. That won't work.
We found a 15 oz can of Green Giant Asparagus Spears that is 5½" tall and the perfect diameter.
There are other brands with the same diameter can, like Best Yet and Flavorite.
You may also find cans that are shorter than the 5½" that we found. That's fine. Obviously,
the longer they are, the easier it is, because you'll need fewer cans.
Just see what your local grocery store has.
The cans must have a flat bottom and top, so that you can remove both the bottom and top
with a can opener. Many cans now-a-days have a rounded bottom, which won't come off easily.
- Cut the tops and bottoms out of the six large cans, so each one ends up looking like a small
tube with no top or bottom.
- Take the small can and poke 6 holes in the top with the other can opener (Figure #3).
These will be those little triangle shaped holes. The top will look kind of like a grill when you're done.
Since this will be the only way that this can is opened, you'll have to shake the conents
out really hard. Do not cut the bottom out.
- Poke a small hole, about 1/8" in diameter, on the side of the small can, toward the bottom. See the
diagram at left. This is the hole where you will pour the lighter fluid through.
- Use the duct tape to attach all the cans together end to end. Make sure you put the small can on the bottom.
The top of the small can (where you poked the 6 holes) will be inside the cannon; you won't be able
to see it unless you look down the barrel of the cannon. The bottom must be solid (not cut out).
After you've got each joint taped good, wrap 2 or 3 layers of duct tape starting above the
lighter fluid hole, and going all the way to the end of the cannon (don't cover the hole).
When you fire the cannon, it gets hot; and depending on the quality of your duct tape, it may melt and get soft.
Having enough layers will keep it solid enough so it doesn't fall apart. Don't be afraid of adding
2 or 3 extra layers.
To fire the cannon, you have to do these steps, one right after another. Don't waste any time moving from
step to step. So, be sure to read through and understand all steps first, before you proceed.
- Holding the cannon upright, squirt about a ½ ounce of lighter fluid into the hole.
You may also try squirting the fluid down the barrel of the cannon. Just try both ways and stick with
whichever works best.
- Grasp the cannon upside down with your right hand and wave it in a large sweeping motion about 6 or 7 times.
This is to get the lighter fluid to spread throughout the cannon. If a few drops of fluid fly out the end due to your
waving motion, don't worry about it.
- Place a tennis ball in the end of the cannon. Just push it down as far as you can with your bare hand. It should
only go about as far as the bottom of the top can.
- Aim the cannon in a safe direction (i.e. straight up).
- Hold the lit lighter up to the small hole in the bottom can. This flame should cause the lighter fluid fumes
to build up, generating great pressure and shooting the ball out the end.
I bought a replacement gas grill starter at Home Depot and installed it on my cannon. This is A LOT easier to
use to fire the cannon, than holding a lighter up to the little hole.
I just mounted the end of the wire inside the bottom of the cannon, so that when you press the button,
it causes a spark to happen inside the cannon.
To make it easy to hold, I also bought a bicycle handle grip (about 6" long), and I placed the starter
inside there. Then I can hold it kind of like a joystick, and just press the button with my thumb to fire it.