Subject: Adapter/beam/plate
From: Rotary Engine
Date: 9/17/2009, 8:43 AM
To: AAA Put this in the To box



Paul


got the files  and have the material here...I have enough to make at
least 8 plates.I will  make 1 for inspection, then if you want
more......

the pressure caps  can be done as well.. get the geom and advise  on
material....

jeff

OK do we have any other buyers? Speak up  now.

Paul Lamar


Paul
 can you publish the list of those that spoke up so we can verify you
have us down... Count me in.

Mike C.

I don't have a list.
People should contact Jeff directly.

jeff doddridge <4starr@cox.net

Paul Lamar


Paul, I was reflecting on the beam plate design, in it's present
configuration. I notice that the Barry cups are in essence butt
welded to the ends of the beam. Given that the welding process
destroys the heat-treat properties of the aluminum in the heat
afected zone, is this method of attachment strong enough to hold
the engine and absorb all of the forces incurred? I'm not an
engineer, but I do understand the welding process, so please
don't take offense. I'm just posing a question.
C. Smith

Absolutely.

If you take a 6.5 G hard landing drop in and assume the engine
weighs 300
pounds the shear force on the welds is 2000 pounds.
Lets assume for the moment all force is applied to only
one cup. The one closest to the engine.

If the total weld area taking both sides of the cup is .25 inch by
3 inch long
that is an area of .75 inch. .125" per side.  Therefor the stress
is 2000 / .75
or 2,666 psi. The  tig weld tensile strength is given in this
referencea about 25,000 psi so we have a factor of safety of 10.

http://www.aps.anl.gov/Science/Publications/lsnotes/ls254/ls254.html

Paul Lamar

 Which is a HUGE under estimate. We are allowed to use 75Ksi in all
 our welds here at my day job. [in 44w plate] W/ 7018 [or equal] welding
materials.
 [We're talking MIG or Stick however.. I'm not sure about tig]

 Fwiw

 Jarrett

 Would/could you please do an FEA with 700 ft pounds of torque combined
 with 1800 pounds of down force :)

 Like Bob White crash. Full power full stall drop in crash landing.

 Paul Lamar

I need to correct this.  The stall was pretty much power off.  I
dropped in from 30-50 ft.  (This is a total guess, but it seemed to
take forever from when it started dropping to when it hit.  I induced
the stall when I reduced power to get down a little quicker as I was
still pretty high and half way down the runway.)  I don't believe the
stall and subsequent contact with the runway caused any damage
whatsoever to the motor mount.  Later I found the tail wheel support
structure was bent. The plane hit tail first.

All the damage was done when I made a dumb decision to try to recover
with a go around.  Now plowing through the weeds at full power, either
the prop tip dug in or the left main caught on something causing the
entire aircraft to rotate about 120 degrees and come to a full stop in
50 to 75 feet.  The composite prop was completely destroyed, the shear
pin on the redrive was sheared, the main gears were ripped off, the
fuselage was bent behind the cabin doors, and the firewall was
damaged.  Damage to the motor mount was the bent support tube as shown
in the picture Paul posted earlier and a slight bend in the MM plate
between the redrive and the Barry mount.

No full stall full power landing though. :)

Bob W.

-- 
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/

If I'm not mistaken, didn't Bob's aircraft have a bolted in barry cup?
C. Smith

Yes it did. Not only was it bolted in but it was slotted in.
Heavier and more expensive. I merely copied the way Questair
did it and used 1/2 inch plate with two 1/4 inch bolts.

Another problem it was a thin mounting so the 2002 rubber bushing
rating was lower than the new cups with the thicker .6" mounting
area. This was discovered by Barry after the Questair
mount was designed.

A third more minor problem was the 1/2 inch plate was in bending
right about where the slot intersected the cup. I was never entirely
happy with that design but it was in common with the Questair design.
Probably the weakest point of the whole design in normal use.

If we still made them that way they would cost even more
as we would have had to start with 3/4" thick plate and mill it
down.

The new design removes the vast majority of bending stress
on the cups and replaces it with a longer welded shear joint
with a lower stress level. As I said it has a safety factor of
ten. I did not mention the welding on top and bottom
areas of the cup which will add to the strength raising
the safety factor even higher.

It never pays to closely design brackets and such
as they are a small part of the total weight.

Paul Lamar


-- 
The Rotary Engine NewsLetter. Powered by Linux.
ACRE NL web site. http://www.rotaryeng.net
Youtube key word UTUBPLEASE
Copyright 1998-2009 All world wide rights reserved.