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, June 30, 2004

Elektra I Prototype Dimensions

Steve -

As promised, the prototype dimensions, including a couple of recommendations for improvements in the design. This should be readable by simply printing the page, or you can access the original size drawing by clicking here and printing it out.

Elektra I Valveless Pulsejet Prototype Dimensions - drawing Copyright 2004 larry Cottrill

The dimensions on this drawing are shown in the form 'inches [mm]'. Note that NONE of these dimensions are critical in any way; you could be off by several mm anywhere and still have a running engine! Some details of construction are critical, however:

First, as mentioned before, make sure you build up a nice big, smooth intake flare as shown. If you don't want to have the primitive fuel pipe permanently anchored in place as shown here, just form the flare without it and file a slot at the lip to hang the pipe in, similar to the way I did it in the edge of the pipe originally. If you use the fireplace cement as suggested here, let if dry overnight before using tools on it. Ordinary metal working files will smooth it up nicely, as needed. The cement is available at places like Menards or Loewe's, in a big tube you put in a caulking gun. It cleans up from your hands, etc. with water.

I originally cut the bottom end of the intake pipe off at a 60 degree angle, to match the angle of the pipe as it penetrates the chamber. I now think it should be cut off at about 45 degrees, so that the opening is more 'shielded' from the blast gas heading back into the tailpipe, as shown in the new drawing. That should significantly reduce the portion of the blast that gets diverted out through the breathing tube. Try it -- you'll like it!

The transition zone from chamber to tailpipe is crudely formed into a 'smooth nozzle' by making the hole significantly oversize and tacking the pipe on with about a 2mm gap between the face of the chamber and the front end of the pipe. Then, after you establish near-perfect alignment with your tack welds, you bridge the gap with a fillet weld all around to finish it up. Sounds tedious, but it's not very many inches of weld, and it's some of the best practice a weldor can work on!

All right, Steve -- that may be enough to get you started on having an Elektra I ready to run by the Fourth of July! Just post any questions you may have as comments, and I'll try to respond as soon as possible.

Go for it!

2 Comments:

At 9:41 PM, Anonymous machine shop said...

Very interesting reading. Thanks.

Sincerely,

Pat
machine shop

 
At 3:05 PM, Anonymous Chattanooga TN said...

Good stuff. Thanks for a nice blog.

Sincerely,

Pat
Chattanooga TN

 

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