Pulsejet Engine Plans
Warning: For educational purposes only! Pulsejet engines are dangerous. They should be built and operated with safety in mind at all times.
Introduction Pulsejet engines are simple in contruction. A very basic discription of the internal contruction is a ventura, fuel syphon, reed valve, combustion chamber,and resonator tube. The function of the engine is not quite so simple. The sparkplug is for starting purposes only. The engine is capable of running due to resonate compression. The sonic wave that is produced by combustion is reflected back into the combustion chamber by the resonator tube. If the resonator tube is tuned properly the sonic wave is reflected perfectly to produce a self sustaining cycle.
Combustion Chamber & Resonator Tube
Materials 2.625" OD x .060" TW Low C/S Tubing 1.25" OD x .060" TW Low C/S Tubing 2.625" OD x 1.25" OD x 2.60" L 14 - 16 GA. Reducer
Construction Cut a piece of 2.625" OD tubing 2.40" long. Drill two 3/16 holes, 180 degrees from each other .25" from one edge. Drill a 1/4" hole 18 degrees CCW from one of the other holes, 1.25" from the same edge. Weld the reducer to the side opposite the holes. This makes up the combustion chamber. Cut a piece of 1.25" OD tubing 14" long. Flare one end to a diameter of 1.50", starting .625" from the edge. Weld the end opposite the flare to the combustion chamber. Grind and polish the welds smooth with the inside and outside surfaces.
Reed Valve
Materials .006 Thick T303 Spring Steel
Construction Cut a circle 2.20" in diameter. Cut ten flower petal shaped reeds to the specifications in the illustration.
Valve Retainer Washer
Materials .25" T6061 Aluminum Plate
Construction Cut a 1.625" disc. Drill a 1/4" hole in the center.
Bevel the edge half the thickness of the disc on
one side leaving a .625" diameter flat surface in the middle. From the opposite side from the bevel, bore a .56" diameter countersink, to a depth of .200". It may be possible to find a stainless washer that can be modified to these specs.
Ventura/Valve Head
Materials 2.625" Diameter T6061 Aluminum Solid Round Stock
Contruction The construction of the ventura/valve head requires the use of a combination lathe/endmill to do a precise work. If you have some experience with building jigs to use with a drillpress. Cut a piece of solid stock to the length of 2.20". All the specs are for the rest of the machining of the valve head is in the illustration. The center hole, for the valve plate retaining bolt and the flow injector, can be drilled first. Then, cut the step for the combustion chamber to slide over. At this point you need to drill ten holes thru the stock at 36 degrees using the specs on the illustration. Next, drill two holes 180 degrees apart,18 degrees clockwise from two of the ten holes previously drilled. These two being 180 degrees apart. Drill these two holes to the corresponding specs on the illustration. Next, center bore from the opposite end from the end stepped to fit in to the combustion chamber. This as well to the specs in the illustration. Blend the inside and outside of the intake to the specs to make the ventura.
Assembly
At this point, if you have followed the directions and done everythings to specs, you are ready for assembly. But first, you are going to need some items that are easier to purchase prefab for this pulsejet. The meter jet, flow injector, and sparkplug are these items. The sparkplug can be purchased at most model shops. All three items can be purchased from Bailey Machining Service. Here is their address and telephone number: Bailey Machining Service, 633 W. Parker Rd, Houston, TX 77091, USA, (713) 694 - 7017. Take the valve head, reed valve, valve retainer, and a allen head bolt 1/4 - 20 UNC x 1/2 and fasten the reed valve to the head so that the reeds are centered over the intake holes. Take the spark plug and install in the 1/4 hole drilled in the side of the combustion chamber, using a nut and sealing washer. Take the assembled head and mount it in the combustion chamber with two #10 - 24 UNC x 1/4 machine screws and corresponding flat washers. Insert the metering set into the flow injector and install in to the center hole at the intake end of the intake end of the valve head.
Starting The Pulsejet
To start the engine you will need a high voltage ignition system, a fuel source and a pressurized air source. Start fuel and air going into the intake of the engine. After a couple of seconds start power to the sparkplug. When you start to hear a pop and then start a low pitch buzz richin the fuel until it sounds stable and then remove the power from the sparkplug. If the engine is tuned properly it should now run on a self sustaining compression cycle, without the need of the sparkplug.
