Monday, April 19, 2010

Making a Toy Cannon (Part 2)

Part 1|Part 2
I've only ever had a few life changing purchases in my life (eg my first car, my wife's engagement ring, that jar of boysenberry jam a few weeks ago...) but my drill press is definitely one of them. The question isn't "What can you do with a drill press?" The question is "What can't you do will a drill press?" (So far, flossing and baking a cake are the only things I've failed at with it.) It has opened up all sorts of toy opportunities for me.
First rule of the drill press - don't be an idiot. Keep that in mind and no one will get hurt. Keep your hands away from the spinning and cutting parts and CLAMP EVERYTHING you are drilling. The bits can create a tremendous amount of torque; don't kid yourself into thinking you can hold something in place while you are drilling it. If you can't clamp it directly, take a minute and make a jig. It is well worth the effort.
Since our cannon has a solid body, we have to bore out the barrel to make it:
  1. Look cooler and
  2. Actually be able to shoot stuff!
Since the barrel has such an odd diameter, we can't just use a spade bit to drill a hole to place it and then lock it in place with a dowel. Instead I lined up two pieces of scrap and drilled a 3/16" hole through both of them. When the boards are upright, the barrel can be locked in place by a dowel straight through one board, through the side of barrel (the trunnion holes) and out the other board. This will keep it locked in place while you drill away.

Here are the measurements that determined what size holes I drilled.
  • The total length of the barrel is 3 7/8"
  • The barrel at its most narrow point is 1/2" in diameter so I went with a 3/8" bit for the bore.
  • The depth of the 3/8" bore hole is 2 1/4"
  • The plunger hole is 5/32"

With the jig firmly clamped to the work surface and the two pieces of the jig clamped to each other around the barrel we are ready to drill.

I drilled the bore first and then I just unclamped the jig and spun the barrel 180 degrees around the trunnion dowel and made sure I was lined up for the plunger hole before I clamped everything again. I replaced the 3/16" dowel as well since the bore passed through it. Hold on to the dowel pieces though, we have use for them in a few paragraphs.

The hole through the breech end of the barrel needs to be big enough that a 1/8" dowel will pass smoothly though it, but not so large that the spring that will live inside the bore could slip into it at all. I drilled a 5/32" hole through the breech until it was all the way through to the bore.

The last bit of drilling is to make a 1/8" hole in the center of a 1/4" dowel. This will be the plug on your plunger and it will live inside the bore. Again, a simple jig is in order. Just drill a 1/4 hole in a board and put a piece of dowel in it. Line it up, clamp it and drill a small hole.

Use epoxy or your favorite polyurethane glue to attach a piece of 1/8" dowel into the hole you drilled in the dowel plug. Make sure you have a good fit. I even lightly scored the 1/8" dowel to give a little more surface area for the glue to adhere to. Let it dry for the full curing time. You want this to be as solid as possible. After it dries, smooth and round off the top of the plug and test fit your pen spring. You might want to flair out the breech end of the spring to be sure it will stay clear of getting in the hole intended for the plunger.

Use a round file (which my dad always called a rat-tail file) to smooth out and slightly enlarge the bore. Take those scrap pieces of 3/16" and glue them into the holes of the side of the cannon. It's fine if they are too big right now because you can trim them to length later. After they have dried though, you'll want to use the file to be sure no glue or pieces of these dowels intrude into the barrel. For the cannon to work its best, you need a smooth bore.

Okay, you are in the home stretch now. With the spring in place, slide the plunger down the bore and out the breech hole. Pull the dowel back and forth a few times to be sure the plunger operates smoothly and the spring is not catching on anything it shouldn't. File and sand as needed. When you are happy with everything, place the bead you are using for the (ooooh, more cannon vocabulary!) cascabel (also known as the round thingie at the end of the cannon) on to the dowel. Pull the dowel back just to when you start to feel that the spring is engaged, and then mark the dowel where the back end of the bead is leaving about a 1/8 - 3/16" gap between the front of the bead and the back of the cannon. Cut the dowel where you marked it and then epoxy or polyurethane glue the bead to the dowel. Let it set up completely before you test it out and make sure that while it dries, it isn't gluing itself to back of your cannon.

Here is the cannon "at rest."
The dowel goes completely through the bead.
(Note the gap between the bead and breech)
Here is the plunger pulled back to its maximum.
It doesn't take much to fling a little ball.

Time to take it out to the test range. I used 1/4" beads and small piece of 1/4 dowel shaped to look like an artillery shell. The range on this test make it seem like this really zings the projectiles, and it sort of does, but that target was really close. When I tested these for distance both types flew a little over 9' 6".

Since everything worked I finished up the kit pretty much as advertised except that I added spoked wheels that I made and put some clementine box wood over the trunnions to allow the barrel to pivot but still stay attached to the carriage. I painted the cannon, carriage and wheels with acrylic craft paint and finished it with polyurethane.

Although I used a $1 kit for this, any piece of dowel more that 1/2" thick could be used following the same plans. The projectiles are really light, but also very small, so don't make this for really little kids. Make sure that whoever plays with it knows you could hurt someone's eye with it and never to point it at anyone. I think that the scale is a little big for 1/32nd soldiers, but not so huge that it looks out of place and couldn't be used.

The finished cannon in all its glory.Remember -
Treat every cannon as if it was loaded.
Making a Toy Cannon
Part 1|Part 2

  1 comment:

  1. Well, well... great minds and all... I've felt inspired by the same kit, not once but thrice!


Just Saying...

While we don’t necessarily need more objects, we just might benefit from more making.
- John Dunnigan


About Me

My Photo
Regular guy who likes to make stuff who lives with a very patient wife, three daughters and three cats.