RADIO INSTALLATION, PART III: Throttle Pushrod:
For the following steps you will need these parts:
•
The fuselage assembly
•
1 - 1/8” od x 15-3/4” Plastic Pushrod Tube
•
1 - 3/16” od x 13-3/4” Plastic Pushrod Sleeve
•
1 - Threaded Stud with Nylon R/C Link
•
1 - Threaded Stud with Metal R/C Link
•
2 - Laser-Cut Plywood Pushrod Supports
•
1 - Throttle Servo (not supplied)
The following instructions describe installation of the throttle
pushrod materials that are included in this kit.
This pushrod
system should work with most 4-stroke or 2-stroke single cylinder
glow engines, like the Saito .91 shown in the photos. There may
be some engine that require a different pushrod arrangement and
different materials (not supplied).
❑
1) Mount your throttle servo in the plywood servo tray inside the
fuselage, using the rubber grommets and mounting screws that
came with the servo. If your engine’s throttle arm is on the right
side of the airplane (like our Saito .91), then you should mount the
throttle servo to the right of the rudder servo. If your throttle arm is
on the left, mount the servo on the left.
❑
2) Drill a 3/16"-7/32” dia. hole through the firewall, aligned with
your engine's carburetor throttle arm. From the front, insert the
3/16" od x 13-3/4” long Plastic Pushrod Sleeve through the firewall
and into the fuselage, back to the throttle servo. Notice that there
is a slot cut in the first fuselage former behind the firewall for the
pushrod sleeve to go through. The slot keeps the pushrod sleeve
out of the area where the fuel tank will be mounted.
❑
3) Inside the fuselage, slip the two Laser-Cut Plywood Pushrod
Supports over the end of the pushrod sleeve.
The plywood
pushrod supports should be positioned wherever needed along the
pushrod sleeve to aim it directly at the throttle servo arm. Once
you’ve determined where to mount them, glue the plywood
pushrod supports to the fuselage.
Note: In the following photos of our Saito .91 installation, you will
see that we glued one plywood pushrod support to the 3rd
fuselage former, and the other pushrod support to the inside of the
fuselage about 2-1/2“ away from the servo.
❑
4) Determine how long the pushrod sleeve needs to be to fit
your installation (we purposely provided it too long so it would
cover most situations). In most cases you will need to shorten the
pushrod sleeve a little bit.
As a general rule, the ends of the
pushrod sleeve should be about 1-1/2” away from the servo arm
and the throttle arm. Use a sharp razor blade to cut the pushrod
sleeve to length. Remove the tube and sand its surface with 220
sandpaper to rough it a little. Reinstall the tube and glue it in place
to the firewall and the plywood pushrod supports.
15
❑
5) Screw the Threaded Stud with Nylon R/C Link into one end
of the 1/8” od x 15-3/4” Plastic Pushrod Tube. Use a needle nose
pliers to grip the threaded stud so you can screw it in at least 1/8”.
❑
6) At the firewall, insert the plain end of the plastic pushrod tube
inside the plastic pushrod sleeve. Push it in until the nylon R/C link
can be clipped to engine throttle arm.
Then reach inside the
fuselage and operate the throttle pushrod tube from the servo end.
Make sure the pushrod can fully open and close the carburetor
without binding.
❑
7) Finish the servo end of the throttle pushrod as follows:
a. Turn your radio on and make sure the throttle servo is
operating in the right direction for high and low throttle. Put the
throttle servo in high throttle position and turn off the radio.
b. Put the throttle pushrod in high throttle position.
c. Inside the fuselage, clip the Threaded Stud with Metal R/C
Link to the servo arm. Hold the threaded stud and the pushrod tube
together and mark the tube for cutting to length. Be sure to allow
for the 1/8” that the threaded stud will be screwed inside the end of
the pushrod tube. Cut off the excess pushrod tube with a sharp
razor knife.
d. Unclip the R/C link from the servo arm, and screw the threaded
stud at least 1/8” inside the end of the pushrod tube, as you did the
other end in step 5. Then reattach the R/C link to the servo.
❑
8) Turn your radio back on and check the operation of the
throttle. Adjust the overall length of the throttle pushrod by scewing
the R/C links in or out as needed to achieve full throttle control.
When finished, secure at least one of the R/C links to it’s threaded
stud with CA glue, so that the pushrod tube cannot rotate in flight
and change adjustment.
