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 U.S. 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 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 long-term reliability, enjoyment, and safety.
The space between the two main rotors has been increased, likely 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, instead of increasing or decreasing the pitch of a 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 when flying the machine.
The main rotor diameter is roughly 13.75 inches. The machine uses 180-size coreless motors to drive the rotors. These motors are chosen for long-term reliability and to provide optimum power for the longest flight time available—usually roughly 15 minutes.
Pluses and Minuses
- Ready to fly out of the box.
- Superb stability.
- Spare parts, tools, radio, and charger included.
- Excellent value and training tool.
- Can’t fly outdoors.
- Tendency to turn left in forward flight.
For beginners the XRB comes with 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 with this machine. Not to worry, though; the manual covers almost everything you might encounter.
Flight Impressions
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 remember that warning.
Forward flight with the heavy flybar weights is extremely slow, and it takes a good amount of control input to coax the model into a turn. I felt that the Sky Robo was too stable for my forward-flight tastes with the heavy weights installed, so I pulled them 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 machine around. They give you a huge 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—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 a great 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 has 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 the 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 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]
Specifications
- 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
Manufacturer
Model Rectifier Corporation 80 Newfield Ave. Edison, NJ 08837 (732) 225-2100 www.modelrectifier.com
Transcribed from original scans by AI. Minor OCR errors may remain.
