Roaring Becomes Elektra Two, Too
Posted: Sat Oct 23, 2004 12:27 am
About an hour ago I got the Elektra II to sustain for the first time, using propane vapor and a ten-inch extension [total length: 36 inches], which is at least a little better than the model I. Though pretty damp, it did warm up a bit today, which got me testing again. A couple of days ago, with about 50 degF weather, I couldn't get anything to go except the old Elektra I at 39 inches. Even the Short Lady wasn't taking any encouragement from me under those conditions. Today it ended up being about 65 degF or so, when I went out there to set up. Unfortunately, I didn't get any photos today, though.
What may be of interest here is the intake treatment. I used 3/4-inch EMT, as you can see in the original prototype photo. However, along the way I pinched a venturi in the pipe out near the flare [this engine has one of my better wrought intake flares] which didn't seem to help at all. So, I went all the way and extended the pinch the whole rest of the intake length, just as tight as I dared and as close to the chamber as I could, to try to get separation of the intake flow at that point. The inside dimensions of the pipe are approximately 17/64 x 1-3/16 [6.75mm x 30mm]! Pretty snug.
The affect of this is that the engine now responds exactly as expected to changes in tailpipe length, unlike the prototype Elektra I, which stubbornly maintained frequency no matter what length tailpipe I tried to use [though it would only sustain after I hit 39 inches]. So, the E II is behaving more like a pulsejet should, perhaps. Getting just the right airflow in was pretty tricky, and I still had to let it warm up quite a while before I could tell it was ready to run on its own. The 10-inch extension has a pronounced flare at the end, just like the prototype tailpipe itself.
Once it was running, I was able to open up the gas a little for better power, and it really seemed to be running full grease, with the chamber and the first 4 or 5 inches of tailpipe getting good and red. I didn't play around with 'throttleability' much, since I wanted to make sure it was really going to sustain indefinitely, which I believe it would have. After a couple of minutes of good running, I tried easing off the extension, which killed the run instantly.
Another important detail is that I was using a severely shortened fuel pipe, which spouts at about 1 inch [25mm] inside the intake rim. This is as close as I've gotten to the nice setup Steve used on his later Short Lady runs.
L Cottrill
What may be of interest here is the intake treatment. I used 3/4-inch EMT, as you can see in the original prototype photo. However, along the way I pinched a venturi in the pipe out near the flare [this engine has one of my better wrought intake flares] which didn't seem to help at all. So, I went all the way and extended the pinch the whole rest of the intake length, just as tight as I dared and as close to the chamber as I could, to try to get separation of the intake flow at that point. The inside dimensions of the pipe are approximately 17/64 x 1-3/16 [6.75mm x 30mm]! Pretty snug.
The affect of this is that the engine now responds exactly as expected to changes in tailpipe length, unlike the prototype Elektra I, which stubbornly maintained frequency no matter what length tailpipe I tried to use [though it would only sustain after I hit 39 inches]. So, the E II is behaving more like a pulsejet should, perhaps. Getting just the right airflow in was pretty tricky, and I still had to let it warm up quite a while before I could tell it was ready to run on its own. The 10-inch extension has a pronounced flare at the end, just like the prototype tailpipe itself.
Once it was running, I was able to open up the gas a little for better power, and it really seemed to be running full grease, with the chamber and the first 4 or 5 inches of tailpipe getting good and red. I didn't play around with 'throttleability' much, since I wanted to make sure it was really going to sustain indefinitely, which I believe it would have. After a couple of minutes of good running, I tried easing off the extension, which killed the run instantly.
Another important detail is that I was using a severely shortened fuel pipe, which spouts at about 1 inch [25mm] inside the intake rim. This is as close as I've gotten to the nice setup Steve used on his later Short Lady runs.
L Cottrill