OK! I cannot stand this any longer - since we are building airplanes,
I doubt that we are using solid bars for this mount - for a rectangular
tube, or a hat section, the major working areas are the top and bottom
"flanges" so for a given wall thickness strength only goes up slightly
faster than linear with increased depth. dig out your old copies of
Rourke, and compute some I over C's for the real sections you are
proposing.
Vance

I did Vance. A hat section with wide flanges is equivalent in "I" to a
rectangular
tube with the lower wall split in half and the parts bent outwards.

For a  one inch high hat section with .0625 wall:

I = (bd^3-b1d1^3)/12

I1 = (2 X 1)^3 = 8    I2 = (2 X 0.875) ^3 = 5.359

I  = 8 - 5.358 = 2.641

Height of beam doubled to two inches high wall .0625:

I1 = (2 X 2)^3 = 64  I2 = (2 X 1.875)^3 = 52.73

Therefor I now equals 64 - 52.73 or 11.27 which is a whole bunch higher
than 2.641!!!!!!

Max Stress = MaxMoment/(I/c) where c is half the height of the flange.


BTW you computer clock is off :)

Paul Lamar

Paul, one difference between a rectangular tube and a hat section is that
with the hat section, the edges are free, rather than constrained by being
joined at the bottom of the rectangular tube, so aren't they more free to
buckle outwards under load than when constrained by being in a tube format?

That said, Jerry's testing is the proof of the pudding in my estimation.

You mentioned stopping by on the way to Oshkosh, we will be leaving to go
north to OSH on the Saturday before Oshkosh, so would you be able to stop by
before that? Would like to have you visit.

Bill Schertz
KIS Cruiser # 4045

Yes you are correct. I few scrap straps as you suggested should  stabilize the
flanges
and solve that problem.

Sure. My itinerary is flexible. I hope to have my Linux laptop up and running
so I can continue the newsletter while I am out of town.

Paul Lamar

-Douglas Fir wrote:

Paul,

The Schertz Beam structure looks interesting.  I have some reservation about
the using the oil pan mounting bolts to hold it on the structure.  Isn't is
a possibilty that their might be some sort of twisting moment applied to
these bolts?

Doug F.- 

Twisting about which axis? The prop torque load is minimal compared to the 6G
down load. You have the one G weight of the engine sitting on the beam
so about two bolts are experiencing about 100 pounds in tension on one side.
The rest are seeing no load as the static weight and torque reaction bear 
directly on the beam.

In gyro pitch there are two clips. One on each side of the beam that pick up
two or three pan bolts on each side. These take the 600 foot pound (CS metal prop)
gyro reaction torque about a vertical axis due to pitch.

This is a very similar design to the QuestAir Venture motor mount. That TIO-550 engine
weighs about 500 pounds and generates up to 600 HP in Reno racing trim.

Paul Lamar

 
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