I wasn't too sure how to organize these posts. As I mentioned, I want to see how various engine setups perform in the pattern. This Forum has a "flat view" of threads (unlike SSW which allows particular posts to start a sub-thread), and if I post all this stuff together, it will be difficult to keep track of the different types of engine runs.
So the topic of this post is Fred Krueger's Magnum 36 powered Tucker Special. Fred has made some modifications of this engine (blocking the boost port and adding some head shims) and has been pretty happy with its performance, first on an Arf Nobler, and now on the Tucker Special. It has no habit of running away. I think he is currently using an APC 10.5x4.5 prop.
I will put in some plots of the various maneuvers starting with the takeoff, and eventually to the clover. The analysis is just that I showed in my Fourier analysis post (
http://stunthanger.com/smf/index.php?topic=14196.0 )with one added feature---I put the actual sound recording device, like before, near the pilot to minimize doppler effects form the airplane velocity. The new feature is that we placed a video camera in the upwind location so that it has a good view of the maneuvering area. This lets me figure out what the plane was doing at the time I am looking at the engine details.
In the plots there are three traces--the engine rpm represented by a white trace, a loudness trace in red (how loud the sound was at the recorder), and in green a trace (labeled "even%") that represents whether the engine is in a 2 stroke (value =1) or in a 4 stroke (value =0.5). Usually the green trace is somewhere in between 0.5 and 1.0 which simply means the power strokes were not exactly equal for each firing. Each time point represents a tenth of a second.
I will mention that during the 1 hour period of the test runs, the wind was an average of ~4mph, with a maximum gust up to 8mph. Pretty much stunt heaven winds.