Plane Talk: Hirobo XRB Sky Robo - 2006/01

52 MODEL AVIATION
Plane Talk: Hirobo XRB Sky Robo
STEVE KALUF
WHEN I FIRST got my hands on
the corded version of the Hirobo
XRB Lama slightly more than a
year ago, I was really excited about
how well it flew. I thought it was probably
the best tool for learning to fly a helicopter
I’d ever seen. The one thing I wish it had
was a cord.
Later in the year, at the
International Radio
Controlled Helicopter
Association Jamboree, I
suggested to Jeff Green of Model
Rectifier Corporation (MRC)—the US
importer of Hirobo products—that Hirobo
should manufacture an RC version. Then
he proceeded to pull a prototype of what I
requested out of his motor home! I knew I
had to have the RC version as soon as it
became available.
The Hirobo XRB SR (Sky Robo) Lama
is the radio-control version of the popular
corded one. This little machine is well put
together. It comes complete with an
adequate four-channel transmitter and is
ready to fly out of the box. You put AA
batteries in the transmitter, charge the
onboard Li-Poly battery pack with the
supplied charger, and you are ready to go.
The Sky Robo has an MSRP of $350
and a street price of roughly $299.
When you open the box you find a nicely
detailed model depicting a full-scale Lama,
training gear, a four-channel transmitter,
an automatic Li-Poly charger, a 7.4-
volt/720 mAh Li-Poly battery pack, braces
for the skids (a necessary upgrade from the
corded version), tools, a blade balancer,
three complete sets of replacement blades,
lightweight stabilizer weights (flybar
paddles), and an instruction manual.
For those of you who are unfamiliar
with the Lama’s configuration, the Sky
Robo uses a counter-rotating twin-rotor
system with a coaxial mainshaft. All
electronics are built into the fuselage.
Since the machine has counter-rotating
rotors, there is no need for a tail rotor.
However, a “for show only” tail rotor is
included to enhance the scale appearance.
Hirobo is the original designer/
developer of the counter-rotating main
rotor and drive system for an RC micro
helicopter. All flying aspects have been
considered, and proper rotor head
adjustments have been provided for longterm
reliability, enjoyment, and safety.
The space between the two main rotors
has been increased. I’m guessing this is so
the more aggressive maneuvers the Sky
Robo is capable of doing do not cause the
blades to hit one another.
Yaw is controlled by the “rudder”
stick, as with any helicopter. However, in
this case, instead of increasing or
decreasing the pitch of the tail rotor to
control yaw, the rpm of the two rotors is
varied to create an rpm differential
between the rotors and yaw the helicopter.
The built-in gyro also works extremely
well. Little actual yaw input is needed
The author and the Sky Robo doing what it does best. This helicopter is solid in a
hover. Tracking of the blades is fully adjustable.
The Sky Robo is a greatlooking
little machine that
even has cockpit detail. It’s
designed to look like a full-scale
Aérospatiale SA 315B Lama.
Photos courtesy the author
• Ready to fly out of the box.
• Superb stability.
• Spare parts, tools, radio, and charger
included.
• Excellent value and training tool.
Pluses and Minuses
+
-• Can’t fly outdoors.
• Tendency to turn left in forward flight.
January 2006 53
Business end of the Sky Robo shows robust gear train. On/off switch, arming button,
and status lights to right of the switches let you know the motor is armed and the
status of the gyro. Servos and electronics are built-in and concealed.
An automatic Li-Poly charger and battery
pack are supplied with the Sky Robo. The
battery would seem to be the perfect
match for this machine.
The four-channel radio and great-working onboard electronics package, providing gyro
and mixing, make the Sky Robo easy and a great deal of fun to fly.
when flying the machine. The main rotor
diameter is roughly 13.75 inches.
The machine uses 180-size coreless
motors to drive the rotors. Yet these
motors are not your ordinary 180-size
variety. Hirobo chose them for long-term
reliability and to provide optimum power
for the longest flight time available—
usually roughly 15 minutes.
For beginners the XRB comes with a
nice training gear and an excellent
instruction manual. As I wrote in my
review of the corded version, read the
manual.
This little machine is just different
enough that any previous helicopter setup
experience you might have won’t be of
much help to you with this machine. Not to
worry, though; the manual covers almost
everything you might encounter.
Enough about the machine; how does it
fly? Great!
You power up the transmitter, then the
helicopter. You must push an additional
button on the helicopter to actually arm the
motors and allow the blades to rotate. This
is a nice safety feature.
Liftoff is a nonstress event. The Sky
Robo takes to the air in a stable manner.
The first foot off the ground is a bit
turbulent because of ground effect. Once
the model is higher, everything is
extremely smooth.
The flybar, in stock configuration, has
heavy weights on it, as does the corded
version. It takes a fair amount of control
input to overcome the stability these
weights offer. Even though this machine is
fixed pitch, it will sit in a hover totally
hands off unless an air vent or some other
outside source upsets it. Even then it is
quick to return to a stable hover.
This is not an outdoor machine. Even
the calmest days are almost too much for
this small, lightweight helicopter. You’ll
probably try it, so just remember that I
warned you!
Forward flight with the heavy flybar
weights is extremely slow, and it takes a
good amount of control input to coax the
model into the turn. I felt that the Sky
Robo was too stable for my forwardflight
tastes with the heavy weights
installed, so I pulled them off and put on
the lightweight paddles that were
supplied. This made the machine much
more responsive to control inputs.
Don’t read this thinking the Sky
Robo turns into a hot rod with the
weights removed; that is not the case. It
is still an extraordinarily stable machine
that will hover hands off.
Forward flight turns are much easier
with the lighter paddles. If you are a
total beginner, leave the heavy weights
on until you are comfortable moving the
Rotor span: 13.437 inches
Weight: 6.8 ounces
Length: 16.875 inches
Height: 7.3125 inches
Radio: Four channels (included)
Motor: Two 180-size coreless
Power: 7.4-volt Lithium battery
Street price: $299.99
Specifications
amount of confidence.
The Sky Robo does have an interesting
characteristic that emerges in forward flight.
When you push it for some speed (which is
still slow, but this model is intended for use
in your living room. Go too fast and you may
find your Sky Robo flying into a wall.), you
have to hold the stick (aileron) to the right to
keep it going straight.
This is directly proportional to the
amount of “forward” stick you have in. Let
go of the right and the machine will do a left
turn! I’m not 100% sure why this happens,
but it may have something to do with the
counter-rotating blades.
Some people have stiffened the blades by
applying monofilament-type tape to them. I
haven’t tried this and feel that it probably
doesn’t provide that great of a benefit.
Yaw control is excellent, not overly fast,
and you don’t want it to be overly fast.
Remember that this is a beginner’s
helicopter.
The beauty of this machine is that you
can pirouette until your heart’s content in
both directions. The built-in gyro does an
excellent job; it holds the tail in the proper
direction regardless of the flight regime.
The Sky Robo blades are made from
molded Styrofoam or a similar substance.
They can break easily; however, that should
be considered a good thing. If you run into a
piece of furniture, you will not hurt it.
Replacement blades are inexpensive, and an
extra three complete sets are included with
the model.
Flying time with the 720 mAh Li-Poly
battery pack is every bit of 15 minutes. I
often make two flights on a single charge.
This pack provides virtually full power up to
the end of the cycle.
The Sky Robo does have a battery failsafe
mode. When the pack reaches the end of
its charge, the motors slowly wind down and
provide for a fairly gentle landing while
allowing you to maintain full control of the
cyclic functions.
The Sky Robo is great fun for the rank
beginner and experienced helicopter pilot.
This is perhaps the best training tool for
learning to fly a helicopter in basic flight. It
will teach you to fly tail in, nose in, and in
every other basic flight orientation. For the
experienced pilot it is a ball to fly around
your house or office at will.
This is not a 3-D machine, but it is great
fun to fly. It has great scale looks, works
perfectly, and is a super value for the money.
If you don’t already own a Sky Robo, it is
worth a serious look. MA
Steve Kaluf
[email protected]