16
❑
1) From the kit contents, locate Bag #18 containing the motor
mount assembly parts.
In addition, you will need the engine
mounting bolts, lock nuts, and flat washers (not included) for your
particular engine. In the case of the Saito 1.00, shown in the
following steps, we used 8-32 x 1-1/4” Allen Head bolts, #8 flat
washers, and 8-32 lock nuts for this purpose.
The first step is to properly mount the engine itself to the motor
mount arms.
An easy and accurate way to do this is to
temporarily mount the two motor mount arms onto a scrap piece of
1/8” lite-ply, cut to a 3-1/2” square. Doing this ensures that the back
faces of both mounts are truly flat in relationship to each other and
the engine when it is eventually mounted in place to the firewall.
Prepare the scrap piece of plywood with accurate horizontal and
vertical centerlines, using a pencil and a triangle. Next, measure
the width of the engine case. For reference, our Saito 1.00 has a
stated case width of 43 mm (1-11/16”), according to the engine
manual. Once you know the case width of your engine, divide that
number in half - again, in the case of our Saito, that number is
.8465”. Mark this dimension on each side of the vertical centerline
on the scrap plywood piece and use a triangle to draw these two
lines. These two lines become the vertical mounting reference
lines for the inside faces of the two motor mounts.
❑
2) Next, the horizontal positioning of the motor mounts is
established. The overall height of the motor mount base is 2.937”,
so round this off to 3”.
As we did in establishing the vertical
mounting location in Step 1, divide this number in half - 1-1/2" - and
make a mark at this measurement on each side of the horizontal
centerline. Use a triangle and pencil to now draw lines onto the
scrap plywood at these marks. With the exception of the four
mounting bolt holes, all of the information needed to accurately
position and mount the two motor mount arms onto the scrap piece
of plywood is now in place.
Note that the two motor mount arms have oblong mounting holes.
These allow the mount arms to be adjusted as needed on the
firewall. When drilling the four mounting holes, use the center of
the oblong holes to allow a little movement in either direction. Drill
the four motor mount holes through the plywood, using a 3/16" dia.
bit.
Temporarily install the motor mount arms to the piece of plywood,
using the bolts, washers and blind nuts provided (thread the blind
nuts onto the bolts backwards, with the flat base against the ply-
wood). Just hand-tighten the hardware for now. Note that because
the engine will be mounted in the inverted position, the motor
mount arms are oriented with the larger of their two webs towards
the top.
Slide the motor mount arms left or right to align them accurately to
each side of the vertical centerline. Once in position, use an Allen
wrench to tighten the bolts just enough to lock the arms in place.
Put the engine onto the motor mount arms. Using a ruler, adjust
the engine on the mounts to locate the face of its prop hub at
5-7/16" from the face of the scrap piece of plywood. Hold the
engine in this position and use a drill bit in each of the engine's
mounting lug holes, marking their centered positions onto the
motor mount arms. Remove the engine and then the motor mount
arms from the piece of plywood.
NOT mount your engine on these motor mounts by drilling and
tapping them for bolts or screws! These mounts should be
drilled for clearance of the engine mounting bolts and the
engine itself should be secured to the mount arms with bolts,
washers and lock nuts. Tapping threads into these motor mount
arms may weaken them, potentially causing them to fail.
Modeler’s Note:
Some engines may require slight
modifications to the motor mounts in order to make them fit
properly. For example, our Saito 1.00 required us to use a
Dremel
®
Tool with a drum sander bit to chamfer the left mount
arm to achieve
clearance for the
throttle arm and the
carburetor body.
The Dremel
®
Tool
makes this quick
and easy to do and
ensures a good fit
to the motor mount
arms. Only remove
enough material
to achieve the
required clearance
and fit.