c) Attach the clevis to the carburetor throttle arm at its
topmost hole location.
Move the throttle arm back toward the
firewall and use a pencil to mark the approximate location of the
threaded end of the pushrod onto the firewall. This is the location
for the required hole in the firewall for the outer nylon throttle
pushrod housing. Disconnect the clevis from the throttle arm. Drill
a 7/32” dia. hole completely through the firewall at the pencil mark.
d) The outer nylon throttle housing tube is now installed.
First, lightly sand the tube with #220 sandpaper to roughen its
surface a bit. Insert the tubing into the firewall, feeding it all the
way back toward the throttle servo. Using 5-minute epoxy, glue the
tube to the firewall, leaving 3/4" of its length protruding from the
face of the firewall. Allow the glue to cure.
e) From inside the fuselage, slip both of the laser-cut plywood
Throttle Tube Mounts onto the throttle tube housing. These mounts
are used to direct and secure the throttle tube back to the throttle
servo. They are glued in place to the cabin former and servo tray
to create a smooth transitional curve back to the throttle servo arm
location. Use 5-minute epoxy or thick CA glue to secure these tube
in the mounts.
down in the servo tray with its output arm facing inward towards the
center of the cabin, as shown. This servo is installed into the
opening that is on the same side as the carburetor throttle arm.
Prepare the throttle servo by first installing the rubber grommets
and eyelets into its mounting lugs. Place the servo into its opening
in the servo tray and mark its mounting hole locations onto the tray
with a sharp pencil. Remove the servo and drill four small pilot
holes for the mounting screws. Using the servo mounting screws
that came with your radio system mount the servo in place.
Now is the time to test the throttle servo for correct movement,
using the radio system. Plug the servo into the throttle channel in
your receiver.
Turn on the transmitter and then the airborne
system. You want to first check the servo to be sure that it's
moving correctly, providing low and high throttle movements that
correspond with the engine throttle barrel. Next, the servo output
arm should be repositioned as necessary to provide equal back
and forth movement. With these issues now addressed, turn off
the radio system.
❑
8) With the engine temporarily in place on the mounts the
mounts in place on the firewall, the throttle linkage connecting the
carburetor throttle arm and the throttle servo can be made.
Our Saito 1.00 is typical of most 4-stroke engines in that its
carburetor and throttle arm is located at the rear of the engine.
This usually places the throttle arm very close to the firewall,
making a "normal" clevis linkage set-up problematic.
Also,
because the fuel tank, when in place in the fuselage, sits directly
behind the engine, it may obstruct the installation of the throttle
tube. With these considerations, we used a reverse link arrange-
ment for our throttle linkage. This installation effectively moves the
throttle tube location away from the fuel tank and also provides a
better, less curved run back to the throttle servo. To do this, it is
necessary to make a pushrod - next to the engine - that reverses
the action of the servo at the carburetor throttle arm. This is done
by using the supplied M2 x 295 mm steel pushrod (threaded at one
end) to create a "U" shaped throttle arm pushrod. From the kit
contents, locate Bag #17 and remove the two laser-cut plywood
Throttle Tube Mounts. You will also need the remaining throttle
linkage parts from Bag #20.
a) Bend and cut the M2 x 295 mm steel pushrod as shown.
Note that the dimensions provided are based on our use of the
Saito 1.00 engine.
Other engine makes may require slightly
different dimensions but the concept is the same.
(insert Photo #70)
b) Using the M2 solder link clevis, solder the clevis in place to
the short, unthreaded end of the pushrod. Note that the clevis is
soldered to the wire with its two arms up on edge.
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