I finally got my Don Swords built C-85 stroker put back on my J-3 and ran it up. The crank/cam alignment is now perfect as it static'ed at about 2425 rpm or so. It started easy and ran up smooth until about 2300 rpm. At that point there was a noticeable oscillation in the sound of the prop and a subtle perception of a vibration at the same frequency as the sound, at about 3 beats per second from 2300 on up to 2425. My mechanic was standing at the side of the airplane and told me he could see the prop in it's plane of rotation, flexing back and forth at that frequency. I wasn't sure what that was all about. We called Don but no answer today. Do you suppose it is the prop that just can't take that much static power ? This particular wooden prop is supposed to be built for C-85 and C-90's and is, according to Don, THE PROP for a C-85 stroker on a J-3. I'm not sure how the max static RPM of 2350 for a wood prop on the TC is resolved. Maybe when flying as opposed to static run at full power, this problem would not exist. I'm not sure because I didn't fly it due to 55 knot wind shear in the forecast and winds aloft at 3000 of 51 kts.
I wonder if this is just a result of a static run with a high power engine with a wooden prop or something deep inside the engine ?
Anyone have any ideas..... ? JimC ?
Thanks.
WV-GWS
I wonder if this is just a result of a static run with a high power engine with a wooden prop or something deep inside the engine ?
Anyone have any ideas..... ? JimC ?
Thanks.
WV-GWS
