DENIS SMITH wrote:

Ken,  What is the design strength of the mount?  Have
you tested it (or do you plan to test it)  to see what
total weight it can carry (g's?)

Denis,
   Does the term 'eyeball engineering' mean anything to you?  I am a programmer
and never bothered to learn how to compute the bending / buckling loads of tubing
despite Paul's best efforts to teach us.  Actually, I did use a chart of bending loads
of 4130 that Paul provided and the lengths of 4130 that I was using seemed so 'over
built' that I didn't bother to calc the rest.  I also tried to minimize the axial loads of
the Barry mounts due to the orientation of the loads (I used four 22002-13 in the
'thin' mount with an axial load rating of 125 lb each.  I also bought two 22002-13 and
two 22002-15 for further tuning if needed).  I did my best to keep the tube lengths
short and used 3/4" .049 for all of the longer runs and 'spread' the mounts as far as
possible (this is a RV-4 - the lower mounts are 21.25" apart and the upper mounts
are 13.5" apart).  So there you have it, nothing too scientific but I did follow the
advice of the engineers who shared their thoughts.  It is interesting that Paul, Monty
Roberts, Bill Freeman and Mike Wills all had reservations about my original plan to
cantilever the lower mount 'only' off the 1983 12a front cover - they didn't trust the
aluminum front cover casting - so I changed the design.

    As you can see from the above, I didn't calculate the max loads of the mount and
I would not have a clue as to how to do this.  I plan to test for 10g's after I get the
engine finished and know what the REAL weight is.  I would guess that the 'long
block' without cooling system will weigh less than 300 lbs, so a load of 2800 - 3000
lbs (10g's) at the engine CG sounds close.  How in the world do you load an engine
mount with a 3000 lb load?????

Ken Powell

Use a car Ken. Don't use ten G's however. Six G's is more than enough. If you use
ten you will break something in the airplane for sure.

Paul Lamar
 
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