Elektra I Jet Engine Builders Web Log

This Web log is to encourage building and experimenting with the world's cheapest working pulsejet engine: the Elektra I(TM) - total cost in brand-new materials: Under $10.00 US, not counting the spark plug.

Want to build your own Elektra I pulsejet, with help from designer Larry Cottrill? Then this page is for you!

Wednesday, July 28, 2004

I built one!


I had been folowing Larry's progress with the Elektra concept since its conception and was delighted when it was finally made to work. At the time I was working on other engines and had no intentions of building the Elektra. However when school let out for the summer and I was suddenly seperated from all my (their) metalworking supplies I became very bored very quick. After keeping myself occupied for a week with a small valveless engine made from short sections of pipe, I remembered the electra which could be built with no sheet metal fabrication and decided to give it a try. Luckily an industrial complex near the place where I work had some old sections of electrical conduit lying around so I was able to aquire them for free. (by the way, did you know that it can be cut with a standard tubing cutter?) I paid about $2.50 for the electrical box and another $1.50 for the cover plate at a local hardwhare store and started working. WARNING: This design requires A LOT of filing by hand so a dremmel tool with lots of bits would be nice to have. (I actually stabbed myself with the file a couple of times while working and don't reccomend it) I just learned how to weld with the oxy torch and am not nearly as skilled as larry is so my tailpipe was attached diferently than his: I carefully filed the hole so that the 1" conduit would fit snugly into it rather then leaving a gap as was reccomended. I also filed the inside of the tailpipe so that it flared outward slightly to help channel the exaust gasses more effectively. I then began to work on the intake flare. I decided not to use the fireplace cement flare because I could just as easily make a flare from some sheet metal I had grabbed from school. the flare was small enough that I could work it by hand without too much dificulty. As long as you measured the intake length and exaust length accurately you should be alright even if all your other measurements are a little off. Just make the layout look pretty close to what you see in the pictures and the engine should run fine. After welding the intake in place I started looking for the cover plate but was unable to find it. Aparently my dad (who is an obsessive-compulsive neat freak and pulsejet hater) threw out my brand new cover plate (with the price tag still on it!). I made him get me a new one and then welded it on. (One note about welding: If you can remove the galvinization, DO SO. Grind it off or soak it in acid overnight, whatever! It is really nasty stuff when it gets hot and leaves ugly white blotches everywhere. The fumes are poisonous so only weld outside if possible.) For the sparkplug I drilled and tapped a hole in the front of the engine and simply screwed it in (this saved me some acetylene). for the fuel injector I reccomend a smal section of 1/4" tubing that is nearly flush with the inside wall of the intake and at a 90 degree angle to it. mount it around 1.5" down from the intake flare. I didn't make a stand for my engine but instead clamped it tightly in a vise (again this saved me some acetylene) To start the engine turn the fuel supply (propane) on untill you can just start to hear the hiss through your hearing protaction. Apply starting air seccond and spark third. For air I used a small tank of compressed air. For spark I used the circut from Bruce Simpson's website (although model T sparking coils are also very popular among pulsejet enthusists). Do not expect the engine to burst into life imediately. Instead it should make frequent bangs and pops and sputter ocasionally. If it does this then continue to let it do so. After about 20 sec. of this it will begin to roar quietly then get louder and louder untill the engine is running completely on its own. At this point take the starting air away and turn off the spark. If the engine dies imediately then increase or decrease fuel flow and try again. You will find the sweet spot eventually. Once the engine is running feel free to play with the throttle settings to see how high or low you can get them, but be careful as too much or too little fuel will kill the engine (although re-starting it when it is hot is much easier)


Overall I enjoyed building this engine and would reccomend it to anyone with some welding experience and some time to kill (or neighbors to anoy) While it is not the best engine for a beginner (due to its difficult starts when compared to some other designs) it could definitely be built and run by one. (And the price is right so why not try it?)

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