George Lendich wrote:

Paul,
Drew in some stiffeners, but not sure if their best placed.
George (down under)

Much better pictures. I am beginning to get the big picture. Since you are
using one large flat area on the front face you will need a lot
more and longer internal ribs. Tracy's psru is only about 6.5 inches (165 mm)

in

diameter so that puts high bending loads into the front plate of your bell
housing.
On the other hand if it is a full 13 mm thick all over it's face
that would be stiffer than what Tracy has now. The big elephant ears
are not useful for mounting as the rubber bushing would be oriented
in the wrong (vertical) plane. They should be accommodated in the
horizontal plane with bolt on brackets to the flat sides.
No real problem as they can be cut off. Ups shipping and
casting cost however. Don't forget to check the exact position of
all the bell housing mounting bolts and make sure you have
material in there to take the bolt compressive loads.

Paul Lamar

********************************************************************************

Okay!!!, NOW we're cooking with gas Guys.....Paul, 13mm thick casting material
is weaker than the same thickness 6061-T6 in Cyclic Flexing which is what this
surface will be exposed to (ie; Drum Skin phenomena)......The way I see a
reasonable solution is to cast on EXTERNAL radial ribs in the top domed portion
of the casting  beginning at the engine mounting Flange and culminating to a
6.250" dia circle in the Shaft's center of the Housing. Do the same on the
bottom horizontal box beam except perpendicular to the bottom, and only a few
Ribs centered starting at the engine flange and culminating same as the upper
radial ones, you'll only need a few, just enough to encompass the The 6.25" dia
of the Psru's arc.

Later when this surface is custom machined, (faced off) then the Ribs can be
bored to the desired ID in the same operation.....IMHO, this is about as STIFF
as one can get it, "Without FEMALE stimulation" :) Pluses: The inside of the
Housing will be clear of obstructions....Will look more professional
esthetically and most important, to coin Paul's phrase......."Too Cool" ;)

The other point I was going to make Paul beat me to; ...Get rid of the Elephant
Ear mounts...Best to provide the side pads for Custom MMs, this way the builder
has the flexibility of designing and orientating to their hearts desire. Just
make sure this area is well beefed up for the Landing loads which will be
imposed on the Pads. Also remove the Radiuses on all the EDGES of the MM mtn'g
Pads, leave the corners SHARP....This will increase the mounting surface area
(very important).

That's it for now.............Butch

According to Jerry's deflection test and Dan's FEA 13 MM >> POCKETED << 
plate is over kill. 356 T6 is what most foundry produce and that is pretty tough. It is a 
bit heavy as is with 9 mm walls (.35"). I think it will be OK without the ribs.
I am afraid if he goes with ribs they will wind up too thick due to
foundry limitations.

BTW for the new folks the deflection is greatly exaggerated in the FEA.
In the actual full scale test the plated deflected less than .5 degree as I recall.

Paul Lamar
 
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