Well, guys. The failure was
not in the yaw mechanism. It was an error in a much more complex assembly,
the installer.
I neglected to secure the back rope for easing the 4 leg tower onto its bolts after I got it pulled up. The angle allowed the prop to hit that rope which was still in place. The rest is history, as they say.
Picture of the nicked rope and where the undamaged prop would hit it is here:
http://www.anotherpower.com/gallery/album123?page=2
Only ever found one tiny piece of the blades its shown in this gallery:
http://www.anotherpower.com/gallery/album123?page=1
Normally this rope is secured close to the tower and tight so its not in the way. Big gouge in the back rope tells that tale quite well. Pretty silly amateur mistake. I checked all bolts for tightness after the vibratory event and all were tight before I put on the 4415 8 foot prop and pulled it up.
So now its got an 8 foot prop on and should be OK til I get a 10 footer sorted out for the new tower.
That prop is documented over here:
http://www.anotherpower.com/gallery/4415-8-foot-prop-project
Maybe I shouldn't be fooling with this stuff but at least its 300 feet from the house.hanks for all the comments.
Tom