Elektra IV 'Black Princess'(TM) Now Being Tested
Posted: Mon Jul 18, 2005 3:47 pm
I just got this one built, but so far have not been able to get it to sustain at any length I've tried. The 750mm length shown in the drawing is definitely not right.
This engine is slim in cross-section, but very blunt-nosed, as the chamber is an ordinary 2 x 4 inch electric switch box. One problem with this engine [and a possible cause of tricky starting] is that the chamber confinement value is very low. It's possible that I should have used 1-inch EMT conduit or maybe even 3/4-inch EMT for this design, to get the confinement up to a more reasonable level. I DO get good roaring out of it, though; it just refuses to sustain. Of course, this has been the story with all of the Elektra series, so there may be some tailpipe length that will get it working once I get the starting air just right.
Note that one other oddment is the fact that the tailpipe protrudes slightly into the chamber, rather than being smoothly nozzled. This possibly could also have profound effects on starting and running, I suppose. It is certainly different from my normal practice of trying to get the smoothest transition I can from the chamber into the pipe.
The reason I built it this way is so I could re-use the intake / tailpipe assembly scavenged from the deconstruction of the original Fo Mi Chin engine, which refused to sustain until it was lengthened to the absurd value of about FOUR FEET overall. You will recall I tore it apart to used the chamber for the vastly superior Fo Mi Chin II, beloved of Bruno. The present engine was very easy to build, since all I had to do was file a big "keyhole" in the rear end of the chamber, weld the pipe assembly in, weld in a spark plug mount and finally weld the solid cover on the top. Then, add my trademark starting air / fuel pipe, of course. Nothing to it, really, all easy smithing and welding done basically in one afternoon.
Anyway, here it is, as originally built. It has been both shortened and extended from the length shown. I am presently working on a larger variety of extensions for the 1.25-inch OD tubing, so that all practical tailpipe lengths can be achieved with some combination of the engine and one or two extensions.
L Cottrill
This engine is slim in cross-section, but very blunt-nosed, as the chamber is an ordinary 2 x 4 inch electric switch box. One problem with this engine [and a possible cause of tricky starting] is that the chamber confinement value is very low. It's possible that I should have used 1-inch EMT conduit or maybe even 3/4-inch EMT for this design, to get the confinement up to a more reasonable level. I DO get good roaring out of it, though; it just refuses to sustain. Of course, this has been the story with all of the Elektra series, so there may be some tailpipe length that will get it working once I get the starting air just right.
Note that one other oddment is the fact that the tailpipe protrudes slightly into the chamber, rather than being smoothly nozzled. This possibly could also have profound effects on starting and running, I suppose. It is certainly different from my normal practice of trying to get the smoothest transition I can from the chamber into the pipe.
The reason I built it this way is so I could re-use the intake / tailpipe assembly scavenged from the deconstruction of the original Fo Mi Chin engine, which refused to sustain until it was lengthened to the absurd value of about FOUR FEET overall. You will recall I tore it apart to used the chamber for the vastly superior Fo Mi Chin II, beloved of Bruno. The present engine was very easy to build, since all I had to do was file a big "keyhole" in the rear end of the chamber, weld the pipe assembly in, weld in a spark plug mount and finally weld the solid cover on the top. Then, add my trademark starting air / fuel pipe, of course. Nothing to it, really, all easy smithing and welding done basically in one afternoon.
Anyway, here it is, as originally built. It has been both shortened and extended from the length shown. I am presently working on a larger variety of extensions for the 1.25-inch OD tubing, so that all practical tailpipe lengths can be achieved with some combination of the engine and one or two extensions.
L Cottrill