Brodhead Pietenpol Association

Original Posted By: Andimaxd(at)aol.com
Max,Now I remember... I think there should be a witness hole up along the threadedpart of the strut bottom about 3/4" or an inch. When you have the clevis in thestrut, a piece of wire stuck in the hole should hit the clevis indicating thatit is in that far or more. Does this make sense? It may be clogged withpaint, etc..Spherical joints also use this witness hole method of ensuring adequate threadengagement.chris ----- Original Message -----

Original Posted By: Christian Bobka
the Piper fork has a 7/16-20 thread. The way I did it was I threaded the forkinto the strut 20 turns... which gave me 1" of contact I can go up to 4 turnsout and still be OK.DJ----- Original Message -----

Original Posted By: DJ Vegh
DJThat is good info. You obviously use 1" less 4/20 of an inch or about 3/4" engagementas a minimum. What is the basis of this?chris ----- Original Message -----

Original Posted By: Christian Bobka
well... first I wanted to find the thread stress area if the fork was threaded1/2" (10 turns) which on a 7/16-20 is .119" =B2/revolution. I foundthe formula for that here:http://www.engineersedge.com/calculator ... o......119 x 10 turns 1.19" =B2I figured 5G's of the gross weight hanging on just one strut fork with the strutat 60=B0 would be 12,000 lbso 12,000/1.19 approx 10kpsi. I'm guessing the lift strut fork has an ultimate shear failure of at least 90kpsi.that leaves me with a factor of safety of 9! and thats if the entire plane ishanging from just one fork which does not happen happens.So then I just figured 3/4" looks about right. :-)DJ----- Original Message -----