perpendicular to the material as
possible. Keep a steady downward
pressure on the tap as you turn it
clockwise. If the tap binds, back it out
and start again. Once the tap is all the
way through the hole, clear the cuttings
from the threads of the tap and back
it out of the hole. If you have never
tapped a hole before, I recommend
you drill a hole in some other material
and practice. Once you get the hang of
it, it’s a real simple process.
STEP 3
Next, you need to attach four 6-32
machine screws to the frame as shown
in Figure 15. The screws are inserted
from the underside of the frame and
tightened. Place a small drop of
thread lock on the base of the screw
near the head. The actual length of the
screw is determined by the thickness of
the material to which we will be
attaching it. In my case, I used a 3/4”
machine screw on the RX- 64 based
Megabot and a 3/8” machine screw
on the RX- 28 based Firebot.
STEP 4
Take four of the included nuts
and insert them into the slots on the
RX- 64 or RX- 28 actuator as shown in
Figure 16. You may want to hold the
nuts in place with a small piece of
tape. While I was assembling my
wheels, the nuts kept falling out.
STEP 5
Place the frame on the actuator as
shown in Figure 17. Using four of the
PARTS LIST
All the hardware can be purchased from
just about any home center or hardware
store. The RX- 28, RX64, and supporting
frame sets can be purchased from
CrustCrawler. The wheels can be
purchased from your local hobby store.
If they don’t stock them, they can
probably order them for you.
On the Megabot, you will need the
following for each RX- 64 based wheel
assembly (six wheel assemblies):
• Eight #6 lock nuts
• Eight #6 washers
• Four #6 by 2” machine screws
• 1/8” thick plastic or wood for
mounting disk (see text)
40 SERVO 09.2008
machine screws, attach the frame. Make
sure you place some thread lock on
the four machine screws. Make sure
the frames are oriented as shown.
STEP 6
For the Firebot wheel, you need to
place the small bushing on top of the
horn as shown in Figure 18. Take the
appropriate actuator and insert it into
the horn as shown in Figure 19. In place,
it will be a very tight fit. I found that if
you work the actuator in and out it, will
be much easier in the future to remove
the wheel. Once seated, take the
included servo horn screw and drop it
through the center hole on the opposite side of the wheel and tighten with
the appropriately sized Allen wrench.
That’s it for the wheel assembly.
For the six-wheeled Megabot, you will
need six wheel assemblies based on the
RX- 64. The two-wheeled Firebot will
require two wheel assemblies based on
the RX- 28 actuator. I recommend you
build the first few wheel assemblies one
at a time until you get the hang of it.
Feel free to use the RX- 28 in lieu
of the RX- 64. Both the actuator and
supporting components are cheaper. On
the same note, you can use the RX- 64
on the Firebot, as well. In both cases, you
can build the Firebot, then later build
the Megabot. If you have never built a
robot of this caliber before, then I recommend starting with the Firebot.
What’s Next
Next month, we will cut the
base assemblies and attach
the wheels. SV
• RX- 64 actuator
• OF-64S frame
• Four #6 3/4” Machine Screws
• DU-BRO 550T Wheel
On the Firebot, you will need the following
for each RX- 28 based wheel assembly:
• Eight #6 lock nuts
• Eight #6 washers
• Four #6 by 2 machine screws
• 1/8” thick plastic or wood for
mounting disk (see text)
• RX- 28 actuator
• OF-RX28S frame
• Horn 28T
• Four #6 by 3/8” machine screws
• DU-BRO 550T wheel
ROBOT CONTROL
MADE EASY
up to
2x120A
- RS232, RC, or Analog input
- Speed or Position Mode
- Dual channel output up to 120A
- Optional single channel to 240A
- Optical Encoder Inputs
- Intelligent Current Limiting
- Thermally Protected
- Field Upgradable Firmware
- Enclosed and Board-Level versions
- and many more advanced features ...
www.roboteq.com
