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How to Make a Jam Jar Pulse Jet

You can make a jet engine that contains no moving parts out of a simple jam jar. It's a simple, valveless pulsejet engine, the predecessor of the turbojet and fan jet, and it can be put together in a few hours. Based on the Reynst combustor, fuel and air provide propulsion as the jam jar jet exhales and inhales fire. Reynst was able to reach 20 "explosions" per second, along with an impressive light show and deep rumble. See how your homemade jet engine compares.

Things You'll Need

Safety glasses
Electric drill with 1/8-inch and 1/2-inch bits
Vise grip
Sandpaper
Pint Mason jar with extra lids and rings
(4) 4-inch pieces of 22- to 26-gauge enamel-coated copper magnet wire with ends stripped
2 DWV (drain, waste and vent) copper fitting reducers, 1 1/2-inch and 1 1/4-inch
Eyedropper marked in milliliters
Gas line antifreeze, such as Heet
Cookie sheet
Fire-resistant gloves
Fireplace matches

Instructions

- 1
  Put on the safety glasses. Place a lid on a workbench and secure it with a vise grip. Use the 1/2-inch bit to drill a hole through the center of the lid.
- 2
  Place the smaller-fitting reducer is a vise grip. Use the 1/8-inch bit to drill four holes, 1/4-inch from the edge of the smaller end of the fitting reducer, and spaced 90 degrees apart. Remove the fitting reducer from the vise grip.
- 3
  Construct the conically shaped jet diffuser and heat sink by pushing the larger end of the small fitting reducer securely into the smaller end of the large fitting reducer. Check for a snug fit.
- 4
  Thread a piece of wire through a drilled hole in the diffuser cone (small end of the small fitting reducer). Bend the end into a small loop and twist the end around the wire several times to secure it. Repeat with the other three wires. Pull the wires so they radiate outward from the diffuser cone.
- 5
  Place the diffuser and heat sink into the center of the jar with the wires over the edge of the jar. Bend each wire over the jar edge to suspend the diffuser and heat sink 1/4 inch from the mouth of the jar.
- 6
  Measure 5 to 10 milliliters of gas line antifreeze in the eyedropper. Squirt enough into the jar to just cover the bottom of the jar.
- 7
  Place the lid on top of the jar. Hold the lid down as you bend the wires toward the center of the lid. Screw on the ring. Bend the wires so they radiate outward. The diffuser and heat sink will remain suspended in the jar.
- 8
  Place the jar in the freezer for two or three minutes. Block the hole in the lid with your thumb and swirl the antifreeze around the jar vigorously to vaporize some of the antifreeze (the fuel). Remove your thumb from the opening and you should feel and hear a release of air. If you don't, block the opening again and swirl the fuel.
- 9
  Put the diffuser and air sink on the cookie sheet. Check to make sure there are no flammable objects nearby. Put on the gloves and light a match. Put the flame over the opening in the lid to ignite the fuel. Back away from the jar.
- 10
  Listen for the jam jar to cycle. It will run at a frequency of about 20 Hz. If you turn out the room lights, you will see a pulsing blue flame under the lid and flames coming out the center hole.

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