Hobbies And Interests
Things You'll Need
Instructions
Making a Sundial
Draw a line from corner to corner (an X pattern) on one of the 10-by-10-inch square pieces of plywood using a straight edge.
Scribe a 10-inch circle from the center of the board using a mathematical compass. Within the circle (360 degrees), mark increments at 90 degrees, 180 degrees, 270 degrees and 360 degrees using the mathematical compass and a carpenter's square. Each marking designates time. Mark one "12." Moving clockwise, label the next mark "3," mark the next one "6" and the final mark "9." Now that you've marked the day into quarter hours, decide how precise you want to make the sundial. Each hour will be 30 degrees from the last, so starting at 12 (12 hours X 30 degrees equals 360 degrees), mark 30 degrees for "1," 60 degrees for "2" and so on. If desired, mark ½ degree for each minute or 2 ½ degrees for each five minutes.
Drill a 1/16-inch hole in the center of the circle. This is where your gnomon, or 1/16-inch-by-5-inch tall dowel, will be inserted.
Determine true north and point the "12" in the direction of true north. A compass will orient you generally by telling you magnetic north, which, depending on your location in the northern hemisphere, can be off by as much as 12 to 20 degrees in the United States. Use a U.S. Geological Survey map to adjust the orientation of the sundial accordingly to true north. Glue the dowel into the hole, and the sundial is ready to go.
Setting up the Cannon
Purchase a cannon to your liking. There are numerous black gunpowder mini-cannons made of brass, cast iron, steel and other metal fabrications for sale at hobby stores and online. The important thing is that is has a burn hole (the hole on the top of the barrel where the gunpowder will be loaded) that is sufficiently wide to allow the sun's focused rays to shine on the powder long enough to ignite it. That can take up to 4 minutes, so the hole should be at least as wide as 2 degrees at the point of light concentration.
Place the cannon outside at noon, about 1 foot away from the sundial, facing away from the sundial.
Mark an "X" using a straight edge on the second 10-by-10-inch piece of 3/4-inch plywood. Drill a 1/16-inch hole in the center. Insert and glue a 4-inch dowel. This will serve as the base for the magnifying glass.
Place an 8-inch piece of flexible crimped tubing that is able to bend but hold its position over the dowel and insert a magnifying glass handle snugly in the other end.
A few minutes before noon, align the magnifying glass with the sunlight focused to a point about 1 degree left of the burn hole. Load the black gun powder if you can obtain it, or Pyrobex, into the barrel of the cannon and use the pusher to pack it at the end at the burn hole. Wad a small piece of cotton or cloth into the end of the cannon barrel and use the pusher to compress the cotton or cloth against the powder. If you don't use wadding, the gun powder or Pyrobex will just fizzle. Wait for noon, and the cannon should sound its alarm.