PyroTechnic Projects: Buzz Bombs / Helicopters
A very popular flying firework, the Buzz-Bomb
The Helicopter is made from a 4 ounce rocket tube (
1/2" ID x 5" long). Like all rocket-type devices,
the tubes used must be parallel wound to prevent bursting,
due to the high internal pressures generated. Parallel
wound tubes do not have the spiral seam that goes down
the length of the tube ( like the tube from a roll of
paper towels or toilet paper has. ).
Propellant: Most rocket propellants are suitable, particularly those that produce interesting sparks. The following composition works well, and several more may be found in the composition database
Clay: The nozzle and end plug are formed from clay, much like as is done in the construction of rockets. As will be described shortly, the nozzle shape is different though. Bentonite, kaolin and ground kitty litter all work well.
Tools: A sleeve and rammer, such as used in the construction of rockets are used for this project as well. Besides a flat-ended rammer an unconventional rammer will also be needed (see figure). With some patience it can be made by evenly filing down one end of a straight rod. Alternatively, you could drill a lengthwise hole of 5 mm diameter in the center of a flat ended dowel and fix a short length of 5 mm rod in that (much like as is done in the construction of a spindle.
Buzzbombs differ from rockets in that the exhaust from the nozzle is projected sideways, exerting a torque. Clay is used to provide a more or less erosion resistant exhaust hole.
Propellant, end plug and exhaust hole
Ram or press the propellant in small increments, each no more than will give a layer as thick as half the casings inner diameter to prevent wrinkling. The other end of the casing is filled with clay to form the end plug.
The exhaust hole is drilled through the side of the casing. This is a somewhat dangerous operation since it causes quite a lot of friction but as we do not need to drill a great length through the propellant and the propellant is quite insensitive, I consider the risk to be acceptable. (of course, a blast screen and proper protective clothing should still be used). Carefully drill a1/8" hole through the side of the casing about 5/8 from the end. Drill halfway through the casing the hole should reach just into the (now propellant filled) cavity in the clay plug, as illustrated.
Wings can be purchased from many pyro supply companies.
Glue the wing to the casing with some hot melt glue. Take care to orientate the exhaust hole properly with respect to the wing.Insert a piece of fuse into the exhaust hole (2 1/2" of visco is adequate) and fix it in place with a drop of hot melt glue
Place on the ground with the casing resting on the ground and the wing on top. Light fuse and get away. Keep well away from these items. They are somewhat unpredictable and may bounce around on the ground instead of climbing into the air. Like rockets, they may explode if the propellant is not compressed well. The end plug or nozzle may also be blown out which can be hazardous.