It is always best to weld motor mount tubes into a cluster of
tubes and not into
the middle of a tube when doing motor mounts for space frame based
fuselage's. Paul.

This is true, but not always possible. The question before me was
could I mount the engine powerfully, starting with what I had
inherited namely the aluminum plate above the oil pan. I wanted to
avoid weaving the exhaust pipes through the engine mount tubes.  The
next moment of reality was when I  positioned the engine and looked
at the options for hooking up.  My engine sets  approximately 3"
lower because of  the off set of the HiVo chain drive (5" offset,
prop is 2" above thrust line, engine top lowered 3.)

   I'm not alone scratching my head.  Looking at the various solutions
or proposals already pictured on the web and the proposals for tying
to the redrive housing, hanging the 13-B is real fun.  I took a shot
at building a truss structure completely under the engine.  The
reason this ultimately proved inadequate was the relatively low angle
of the lower brace. It  just did not have enough leverage. I think
the concept could be made to work very well with a planetary gear
drive as this would move the engine up about 3". In my case it  was
easier to just put in the single diagonal brace which   locked  the
entire structure as you would imagine.  I put it between the exhaust
ports and made sure there was plenty of clearance.  The lower
transverse tube across the bottom of the fire wall rather than
carrying the load at  its  center actually  has the load distributed
along its length and each load point is braced to another transverse
tube which is in turn  braced to a third.  

This is what  you go
through when a cluster is not convenient. The upper  diagonal tube
which was added later  takes the load off of these completely and
makes the whole effort somewhat redundant.    The upper lengthwise
tube that the engine sets on  anchors on the gear receiver  (at this
point to  just a single tab but will be a boxed, rigid structure when
finished) For anything to move at all, the entire landing gear
support structure would have to be ripped out by the roots.
Enclosed are additional photos with the engine removed.  You had a
discussion when I first tuned to this list, something about engineers
vs. back yard fabricators.  The consensus was that a combination of
these skills was the best.  I fall into the back yard variety .  I
sure wish I was a better engineer.  I appreciate your comments.
Jerry

Its not all that bad Jerry. I would not give up on it. As you say you
will have to weave everything around those diagonal braces.

Here is my suggestion for beefing up that lower lateral tube. The braces shown
can be 1/2 inch .049 if you wish. The top of the sockets for the landing
gear are real strong so just a few gussets up there will make a world
of difference in the strength of this motor mount.

Paul Lamar
 
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