On the Glass Goose mounts we've developed, there are two horizontal
beams made of 1x2x.065" 4130.  The rear mount has 4, 6mm bolts and 4,
8mm bolts into the rear cast iron housing.  The beam is about 18"
long.  I welded a pair of short sections of 1x1.5" 4130 perpendicular
to the rear beam to allow it to pick up the extra pair of 8mm bolts in
the rear housing, as well as one more 6 mm bolt in the rear rotor
housing.  None of these bolts has more than a 1/2" grip into the
housings, but I'm satisfied this mount is plenty strong.

On the front mount, the beam itself can only pick up 6, 6mm bolts that
grip 1/2" of the aluminum front housing.  This beam is about  24" long,
and will accept most of the torque loads.  I know the bolts are strong
enough for most of the loads, but was concerned that some maximal
forces might be too much for the aluminum bolt holes.  I noted there
are two left, and one right, 10mm bolt holes in the front cast iron
housing on the Renesis that are very close to the front beam.  To
experiment with how these bolt holes might be utilized, I welded two,
90-degree plates of 0.10 4130 to the beam, as per the pic.

My poor welding technique ended up with a couple of mm of distortion of
this beam, which pulled the mounting holes out of alignment.   This is
no big deal or expense to rebuild.  However, I would appreciate some
input on whether the extra strength of the side plates might be
worthwhile or just overkill.


Scott Gettings

90% of the up and download load is on the rear cast iron end housing.
The front up and down load is near zero. The front mount
reacts prop torque mostly. Hard to say exactly because it
depends on the exact hardness of the rubber bushings.

Three rubber bushings are much easier to analyze.
One assumes the single front rubber bushing mount
takes no prop torque. The vast majority of the prop
torque is taken by the two widely spaced rear mounts
along with 90% of the up and downloads due to high G
turns and heavy landings.

--------------
I think you need internal to the beam bracing to keep the bolts from
'collapsing' the 1x2 square tubing.

Bill Schertz


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