George;
Let me first set a misunderstanding that keeps bouncing back and forth
between you and Mike Collier:
Mike COSMAN of Rhyolite Aviation (Father & Son team) are the designers
and
builders of the 20B powered Big Husky Boys aircraft.
www.microcosman.com/aircraft
Musings/Clarifications/Suggestions/Questions:
Ah Ha! I was starting to get somewhat suspicious about my possible
confusion, in regard to this.
My apologies to Mike C.
-The sharp corner at the shoulder of the of the Engine Bkt's surface's
"Shear
Stop" should DEFINITELY be avoided.. ..A cutter with a 3/16 radius
(minimum),
must be used so it can be machined in SIMULTANEOUSLY. What this implies
is
the cutter itself must have the 3/16 radius ground on, and cut in the
same
operation while cleaning up the complete mounting surface.....Which
leads me
to:
Again my suspicions confirmed - thanks!
-Are the Mounting Bkt. surfaces going to be machined perpendicular to
the
Psru's mounting surface??......Or are you planning to just "Machine
Clean"
the existing angular "Draft" surface??.......Or am I missing something??
Well I wasn't going to, but now you mention it, I can see your point, I will
check to see what extra I have there, perhaps 1 mm and make a clean sweep on
both sides.
-Since Tracy's Psru mounting bolts are through mounted with locknuts &
flat
washers, the .250 dia holes MUST be "Face Spotted" with a c'bored on the
inside of the Bellhousing PERPENDICULAR to the Psru's front mounting
surface.
This step can be easily performed on a decent drill press with a Pilot
C'bore.
THIS PROCEDURE IS VITAL IN PREVENTING A BENDING LOAD AT THE WEAKEST
POINT OF
ANY BOLT (Root thread) AND AT THE WORST PLACE OF THE JOINT (Between the
nut/washer bottom surface and the irregular top surface of the casting)
at
initial torquing of the bolts.....This, in my book of experience is NON
NEGOTIABLE....So George if your Bellhousing is not compliant to this, as
far
as I'm concerned it won't even make a good "Boat Anchor" as it will be
much
too LIGHT ;-)
Understood !
....Tracy's plate has parallel sides so he didn't have to worry about
this.
-George I must clarify the following item for the record and future
production units....In early transmissions I voted for having the Psru
Mounting Hub net excess (Hub minus Housing thickness) on the FRONT
SURFACE of
the Bellhousing.....The counter argument ranged around the fact that it
would
extend the Psru forward....My point was/is that when the front surface
is
partially machined (Sans the Hub) stress concentrations can be created
at the
juncture of the machined surface and virgin surface, especially if it's
an
under-cut like in our case. This is certainly NOT a good place for this
phenomena to be allowed to reside in. However this can be easily avoided
by
providing some kind of protrusion in the front surface of at least
3/16th of
an inch prior to machining, and simply do away with the phenomena
alltogether.
Butch, I agree entirely! However we have the problem where I'm trying to
accommodate Tracy'sdrive shaft length and the starter motor on the same
plane ( level surface). I agree I hate stress risers, my personal preference
is for the pad on the face for my Aussie option.
The way I see it, is....If anybodys aircraft/installation is
that critical to dimensional tolerance & CG variation of 1/8 of an Inch,
that
plane should not be flying and instead be anchored to the ground for
birdies
to do their daily doody deposit on :-)
Looking at the bright side,...Gentleman/Ladies, we are already talking
future
production here :)
So bring on the next dificulty, (Hate the word "PROBLEM") ;)
Butch
The stresses in this area are low Butch. Not to worry.
George, here is a quick and dirty way to test the strength (not the
deflection).
Feel free to jump up and down on it.
Paul Lamar
Paul,
Thanks mate !
George (down under)
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