Paul,

 I drove out to the airport this morning and inspected the flex plate on my
 p-port 20B the best I could with everything assembled.The bad news is
 that it does appear to be cracked in at least one place down near the
 counter-weight area.  The good news is that I found it on the ground.  I
 will be removing the psru today and will report on my findings at that
 time.

 Mark S. in TX
 3 rotor P-port.


 That confirms my suspicion where the cracks are starting. We all owe Dave
 for finding this out.

 Dave do you have any more info on that $200 chrome molley flywheel?

 Paul Lamar


 Paul,

   What do you think of the idea of making some plugs to fit inside the
   lightening holes and TIG welding the plugs into the holes, using a new flex
   plate of course.  If you're careful, it won't turn it into a pretzel.

   Mark S. in TX

   I think it would help but making your own gives one the flexibility
   to change the thickness at will.

   I think just one piece of .090" 4130 would be lighter. We don't need
   the clutch wear surface. 12 inch diameter disk of steel
   would be:

   A = pi x r squared.
   r = 6 inches.
   r squared = 36
   Times pi = 113
   Times .090 thick = 10 cubic inch
   steel weighs .3 pounds per cubic inch
   so it is 3 pounds. Less ring gear.
   You could go up to .125 thick and still not weigh the same.
   14 cubic inch times .3 is 4.2 pounds.

   Not counting the large hole in the center or the 7/8th inch high aluminum
   ring.

   I say make it.
   It is the holes that are starting the cracks.

   Paul Lamar


 Paul
 I just wanted to confirm that the installed flex plate also included the
 additional 4.5" dia plate which is a required  part for the automatic flex
 plate. (Not shown for a manual trans.)
 If the high strength bolts are only installed on the flex plate and not 1st on
 the small dia plate then there will be cracking.

 John P           

          Paul
Could you ask Dave Leonard whether he installed the item 24 back plate shown in the above attachment. Non installation of this would affect the stress fractures of the automatic drive plate aka flex plate.
It would affect my decision on my presently planned Oshkosh flight.

John P
               
I am sure he did. We all do that I think.
You are right. It will crack sooner rather than
later if that is left off.


Paul Lamar