In article , "Jeff Crowell"
wrote:

Mike Marron wrote:
I doubted that ... B) the pod fasteners were designed to take
shear loads in the threaded area.

I did not "doubt" what you said about them "four bolts running
straight up into the airframe."

FYI, Mike, shear loads are 90 degrees to the long axis of the bolt.
Loads aligned with the long axis of the bolt are tensile loads.

I read that whole convoluted thread with amusement earlier this
week when I returned from travel. So much figurative arm waving...

As a long time mechanical engineer, let me point out a few things
I saw when reading the whole distended session:
1] someone (MIke?) was absolutely correct when he said that bolts
should never be loaded in shear across the threads. There are
special bolts with unthreaded shanks for shear loading.
2]someone said bolts are roll threaded to increase strength, that
is incorrect. the reason roll threading is used is that it does not
create as bad a stress point as cut threads. Cutting threads cuts
across grain flow and roll threading pushes the grain around the
thread. No increases in strength, but less of a decrease.
3] It is perfectly reasonable that 4 bolts going straight up into the
airframe take the entire loads of a pod. Pod mounting points are
primarily loaded in bending with only a little shear. This is overcome
with tensile strength, not shear strength.
4] any good designer can transfer pod flight loads into the airframe
anyway, without putting the entire load through fasteners
5] cadmium is plated onto fasteners to prevent galvanic corrosion
with aluminum in the airframe
6] pre-loading the bolts puts the structure in compression.
Subsequent flight loads unload the compression before the
structure goes in tension. All this depends on the load paths.
7] I have some experience with "little hooks" and different alloys
and different heat treatments. Size doesn't necessarily matter.

ciao

--
Harry Andreas
Engineering raconteur