Part of the day

[Mark]

If anyone lives near a large marine center or boat junk yard, you might be able to use reeds like these for some sort of pulsejet. I have a graduate thesis where the student used similar reeds on a trombone adjustable length tailpipe. He's the one who had the charts and graphs on various shaped pulsejets from around the world. The cones, the two part and three part pulsejets. He made some valves himself and also used "store-bought" ones. Not a lot else in his report that would be new for us or I would have mentioned it.
For the most part, pulsejets are pulsejets. Yet what looks simple on paper is often tricky getting there. Yesterday I toyed with a single petal valve for a tiny store-bought pulsejet that had junk for a reed and broke the day I tried it. Threads were striped, the petal rattle inside the jet, etc. No wonder he sold it to me as new, never been run! So I have to make a reed and head for it myself. And then I experimented with another pulsejet and new kind of reed for a pulsejet I had made that ran on a different reed long ago. I spent the day trying to get a simple single petal to do its stuff, yet encounted endless problems with both engines.
Was it getting too much fuel, was the retainer too high, was the reed too stiff, was the length of the intake too long, was the humidity too high, was the reed the right shape for the hole, was it the right size for the jet, was the jet air tight enough, was the fuel port too far or too close to the reed intake, etc.
Twice on different occasions, I got some stunning one seconds revs but the valves came loose or developed chips in the edges, I used both .004ths and .006ths in this case. Later in the day I used a .010ths reed. Then I had to drill and tap some holes, finding the right screws, drill sizes, etc. I broke a tiny tap using a giant tapper that wasn't sensitive enough to feel the torsion and I sheared the little tap in the hole I had just drilled.
Ah, just a simple single petal valve. The price of a single cup of coffee comes to mind, (Mike's quote on opinions). If you haven't been there in uncharted waters, you probably don't know for certain. You've got to love these little pulsejets.
Mark
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