center or they will cut into the rubber on the tire. An 11 mm
hole is a good starting point, but if you use a different
wheel type or size you may want to make adjustments.
Using a 1/8” drill bit, place a starter hole at each mark
as shown in Figure 5. These holes should only be about
1/4” deep. Drill them at a 90 degree angle to the wheel.
In other words, make them perpendicular to the wheel.
Now take a 5/32” drill bit and drill the holes all the way
through. Take it very slow and move the drill in and out as
you proceed in order to clear the debris. It’s very important
that you keep the drill as perpendicular as possible. If you
have a drill press, this would be a good time to use it.
The bit may drift a little as you drill the holes. It’s okay if they
don’t appear on the opposite side in the exact same location.
These holes will be used later to attach the disk with 2 inch long
#6 machine screws. Figure 6 shows the finished holes.
be 5/16” in order to fit the smaller horn.
Place the horn in the hole as shown in Figure 9. The
holes are in sets of three. You will be using the rightmost
holes. Mark each of the holes with a pencil.
Remove the horn and drill a hole at each mark with a
7/64” drill bit. Use a 5/64” bit if you are using an RX- 28 horn.
Important: If you are using an RX- 28 horn, the small
screws that come with the horn will not be able to reach the
horn because they are not long enough. On the opposite
side you will need to countersink the holes (see Step 8).
Using four of the smaller machine screws that came
with the servo, attach the horn to the disk as shown in
Figure 10. It’s important that you add some sort of thread
lock to the wheels or they may become loose and fall out
over time. For the RX- 64, tighten the screws until they are
Take one of the disks and insert it into the
center of the wheel as shown in Figure 7. Make
sure you are using the same side of the wheel
that you marked previously. Place an index mark
on both the disk and wheel as shown. This will
help you line things up later. Attach the disk to
the wheel using four pieces of tape.
Take the long #6 machine screws and insert
them into each of the holes on the opposite side
of the wheel, including the center hole. Press
firmly and twist. You want to make marks on
the disk as shown in Figure 8. Using the 5/32”
drill, place a hole at each of the outer marks.
Drill out the center with a 3/8” drill bit also
shown in Figure 8. At 3/8”, the horn will be a
little tight, so you will have to enlarge the hole
slightly. You can use a knife or slide the drill bit
up and down the hole while slightly skewing the
disk. If you are using an RX- 28, the hole should
SERVO 09.2008 37