> Does anybody know the provenance of this bolt? It looks
       aerospacey.
             > The letters on the head are B30US8 and the other edge has a
       cursive
             > type 'A'
             > I was wondering about using them for mounting the motor.
             >
             > Chris Cosman
             >
             > Chris,
             > By the large radius under the head, it is most likely a
       structural
             > bolt.
             > If you have a spare, you could hardness test it.
   Probably way
             > stronger than
             > you need.
             > Larry

             > Its a nickel alloy 718 bolt, 1/2-20 UNJF-3A thread, with 220
       ksi min
             > tensile and 125 kis min shear strength (very strong,
   well above
       grade
             > 8). If its used in high fatigue applications, it should be
       limited
       to
             > about 114 ksi.
             >
             > John Bell



            Thanks John.  Where did you get your info?

            Chris


       I agree that that's a high temperature Inconel 718 bolt.  I have the
       spec in
       my office but I'm snowed in so far this morning.

       The issue is that it does you no good without the nut.  I'll get the
       spec on
       those, too.

       -Ben


   I recently replaced the bushings that isolate the steel tube motor mount
   from the aluminum fuselage on my 182.  I was sort of disturbed by the by
   the seemingly small size of the bolts used for the task.  There are a
   total of four (I think) AN-4 size bolts holding 450+lbs of shaking and
   shivering Continental to the front of the airplane.  Granted, the mount
   design takes advantage of good structural efficiency - a big firewall
   allows good triangulation angles.

   I don't know the purpose of using this kind of bolt for a motor mount..
   Unless you're on an aggressive, airframe-wide campaign to reduce weight,
   going to something exotic doesn't seem like it's going to be worth much,
   and likely just makes future service more annoying - should the bolt
   ever get lost or damaged.  Even if the bolts are free, similar AN bolts
   of known provenance can be had for a reasonable price.

   I guess if you're having to make up for another design compromise - bad
   mount geometry or having to run an exhaust stack too close to the bolt -
   exposing it to prolonged high-temperatures maybe it's a deal.


   Regards,

   Matt-

   If it is bad mount design geometry the surrounding structure will
   probably fail
   before the bolt. Here are some bad MM ideas :)
   --
   Paul Lamar ...No rotor no motor.


Cool shots.  Really shows the benefit of the Shertz Beam concept -
cantilevering the bell housing end mounts away from the engine by a
fairly small amount allows for much better tubing geometry.  I like this
one too:

http://rotaryeng.net/Left-side1.jpg

Though all the machine work on the aluminum plate isn't as cheap as the
bent channel of the Shertz Beam..

It would be cool to have a big compilation of pictures of good and bad
motor mounts with critiques on each.  It would be nice if the bad ones
had doodles on them showing where they would likely fail in service, and
ideas for how to correct them.


Matt-

Good idea Matt. All those pictures I just uploaded were compiled
over ten years. I made a folder of bad designs and put things
in that as they developed.