I finally got around to building a thrust test bench, like I said I would a few months go. Some ball bearing drawer slides, scrapwood, fish scale, etc...
So...the Kamdax, after having tested four different units, gives out fourteen ounces of thrust.
I tested the tuned pipe extensively...no increase in thrust. And no "sweet spot" where I can hear it coming up on the pipe. Very interesting. I need to work further on that.
The Kress rotor gives only 11 ounces of thrust. Wonder if it gives a higher exhaust velocity, though?
It did not occour to me at the time that I have a Kestrel wind meter in my field box that could have given data on that. But my ears were ringing anyway, that was enough for the day.
Testing engines is noisy and annoying.
Same test bench can be used for all my stuff, turbines, whatever, and it only cost $30 or to to put together.