April 4th, 2008 captain
A tiny, low cost, easy to fly helicopter, suitable for the office or living room, the Silverlit PicooZ was one of the big gadget hits of 2007. It has sparked a number of imitations, but still remains the iconic image for micro sized helicopters.
As is typical throughout the Silverlit range, the box contains everything you need to get flying. There is the PicooZ helicopter, a combined two channel controller and charging station, a spare tail rotor, some sticky aluminium pads for flight trimming and the instruction manual. All you have to supply are six AA batteries and a small cross head screwdriver to fit them.
Configuration
The PicooZ is conventionally arranged with a twin blade 132mm diameter main rotor and 30mm tail rotor. The all-up weight is 11 grammes. The EPP foam fuselage houses the battery, electronics and the motor that drives the main rotor through a large gearwheel. The gearwheel is visible, but protected by clear mouldings. A plastic tail boom protrudes from the rear of the fuselage supporting the tail motor. From the side of the fuselage protrudes two stub wings that act as landing gear. On the starboard side the recessed on/off switch and charging socket.
Above the main rotor there is a small weighted propeller the fulfills the role of stabilizer (or fly) bar. It connects to the main rotor using small struts such that rocking of the stabilizer changes the main rotors pitch. By acting as a gyroscope the spinning weights keep the helicopter flying level.
Controller
The infra-red controller doubles as the charging station for the PicooZ. A hatch on the controller slides down to reveal an umbilical cable that plugs into a socket on the PicooZ’s fuselage. With the power switch on, the charge LED will illuminate until the battery is full.
The controller has two levers: the left stick operates as a throttle for the main rotor to control climb and descent; the right stick operates the tail rotor to control direction. Both are spring loaded to neutral. Below the tail rotor control are two trim buttons. These are used to keep the fuselage pointing in one direction with the tail rotor control set neutral. They are set my multiple presses and will have to be adjusted each time the main rotor speed changes.
The final switch on the controller is the channel selector. This should match the channel printed on the underside of the PicooZ’s fuselage. In this case channel C.
Airspace
The PicooZ’s manual recommends a room about 3m x 5m x 2.5m. Personally, I would say that, once past the beginner stage, any CLEAR space where you can stay more than 2m away is OK. So bedrooms, lounge, office or cubicles are all possibilities. I’m sure this has been part of the PicooZ’s appeal. The manual doesn’t quote a maximum range for the transmitter, although the Amazon product page quotes 10m. One thing to avoid is a room with strong air currents. My normal flying space as some high top opening windows for ventilation. It they are open the PicooZ can be sucked towards them from a couple of metres away. The only way to stop it being sucked outside is to cut the throttle and plummet earthwards. The strong sunlight through the windows can also cause the PicooZ to fall out of the air as the sun’s infra-red overpowers that from the controller.
Flying
All charged up and switched on the PicooZ was placed on the floor for the first flight. Having never flown a helicopter before and not wishing to risk damaging it, the main rotor was throttled up slowly. As lift overcame gravity the PicooZ started to skate around the floor until powered down to avoid the rotor hitting a desk.
For the next attempt more throttle was added to get it flying out of ground effect. It rose quickly pirouetting around its axis. To avoid the ceiling the throttle was reduced causing the PicooZ to plummet. After a couple more attempts and able to hold a reasonably constant altitude it was time to stop it spinning. The right trim button was pressed repeatedly until a constant heading was achieved.
Here the limitation of the two channel control becomes apparent. You can go up and down and turn left right, but how do you make it go forwards? Here you have two options.
- Single rotor helicopter dynamics are such that the PicooZ will move slowly forward during a gentle clockwise turn. Reversing the turn will cause it to stop. By repeating this technique the PicooZ can be made to fly in circles. However, its slow going and you soon get fed up.
- The second method uses the self-adhesive aluminium pads supplied in the box. Fixing them under the nose of the PicooZ shifts the centre of gravity forward. The resulting tilt of the main rotor means that some of it’s lift acts to push the helicopter forward. You need all three pads to see the benefit. The problem with this technique is that you loose the ability to hover whilst keeping a constant heading. To stay over one spot you have to keep it turning in small circles. I would still recommend this solution though.
Towards the end of a flight you will find yourself adding more and more throttle to maintain height. Before the power is totally exhausted bring it in for a safe landing. Before recharging the PicooZ give the battery 10-15 minutes to cool down first. This will extend it’s life significantly.
Unlike the Palm-Z, there are no surprises in the PicooZ’s flight envelope. It’s behaviour is predictable, although fine control takes practice. Without a gyroscope connected to the tail rotor every speed change of main rotor causes the PicooZ to yaw. With experience you learn to compensate for this with the tail rotor control.
After only a couple of flights I found myself attempting spot landings and flying between the cables holding up the suspended lighting. Sometimes I would clip a cable, causing the PicooZ to fall to earth and each time no damage was sustained. As yet I have not needed the spare tail rotor.
Another challenge is to fly really close to the ground: less than 100mm (4 inches). On carpet especially the ground effect causes a strong yaw, the severity of which varies sharply with small changes of height. Flying in straight line requires a lot of concentration. Ground effect also adds to the fun flying over a table. Flying onto the table causes a sharp yaw and slight climb and then as ground effect is lost flying off the other side it can drop out of sight. These challenges and more serve to extend the interest span of the PicooZ.
Conclusion
The PicooZ has become one of the most desired ”big boys toys” and for good reason. It provides a lot of fun in a small package without needing a large operating space. There is extra satisfaction in that the fun happens in the real world instead of on the virtual 2d world of a computer monitor.
I have now flown a couple of other 2 channel electric helicopters, but for now the PicooZ remains the favourite with it’s predictable and reliable operation. Each of the others have had some failing that spoils the experience. More of that in future reviews.
Following the PicooZ’s success the range has been extended with versions featuring Huey and Apache gunship style fuselages, insectoid fuselages and for the competitive the Sky Challenger twin pack. With this set you get two helicopters and controllers on different channels that can be flown together. Each helicopter has an infra-red emitter that if aimed correctly, will cause the opponents helicopter to cut out and fall to earth. The spare tail rotors may come in handy.
Facts and Figures
Whats in the box
- PicooZ helicopter
- Combined infra-red transmitter and charging station
- Multi-language manual
- Trimming pads
- Spare tail rotor
You have to supply
- 4 x AA batteries
- Cross-head screwdriver in order to fit them.
Dimensions
- Main rotor diameter: 132 mm
- Fuselage length: 170 mm
- Height: 70 mm
- Weight: 11 grammes
Manufacturers Website
Available in the UK From
Posted in 2 ch, Helicopter, Indoor, Review | No Comments »
March 19th, 2008 captain
The Palm-Z is a tiny single engine biplane designed for indoor flying. Everything you need to get flying is included in the box with the exception of four AA batteries. The multilingual manual features the unfortunately now common poor English, but with the pictures everything is clear enough. As will become clear latter, it is also worth investing in a roll of “Magic tape”.
With a 210 mm wingspan and 6 gramme all-up weight, the airframe feels fragile in the hand, but being it’s so light, will tend to bounce rather than crunch as long as it’s not diving under full power at the time. Any small cracks that do appear in the EPP wings can be repaired using the included self adhesive strips.
Aircraft Configuration
The Palm-Z has a stubby fuselage the houses the battery, receiver, motor and propeller. This also includes the power switch and charging point. The wings are attached top and bottom and then further braced by the twin booms running back to the tailplane. A pair of thin wires are routed along one boom to control the single central rudder. The rudder has a small magnet mounted forward of its hinge, sitting inside a copper coil. Varying the current in the coil changes its magnetic field and so pushes the rudder left or right. The fin is angled on the tailplane to prevent a turning force due to the spiral airflow in the prop-wash.
The motor drives the rear facing propeller through a large gear wheel. This increases propulsion efficiency as, for the same motor, a larger slow turning propeller produces more thrust than a faster small one. The downside is that gearing produces more noise. In the event of a crash, damage to, or from, the propeller is minimised, being enclosed by the wings, tail booms and tail surfaces.
Controller
The infra-red controller has a cradle where the palm-Z sits for charging. Once placed, move the power switch to the charge position and when the green LED goes out you are ready to fly.
The flying controls consist of throttle and rudder; both are spring loaded. The throttle is used to control climb or descent, the rudder direction. There are also a pair of trim buttons for the rudder. These allow you to get the aircraft flying straight with the Rudder set at neutral.
Before flying it is worth checking that the channel selector on the controller matches that printed on the underside of the lower wing. In the example below – Channel B.
Airspace
The manufacturers website quotes a minimum room size of 2.8m square although this would restrict you to flying in small circles. The manual recommends a room 6m x 7m x 3m which is more realistic. The transmitter has a quoted range of 5m so a 10m square room represents the upper limit. Any bigger and you are likely to lose control if the plane goes out of range. As the control system uses Infra-red to transmit signals to the aeroplane try to avoid rooms with strong lights or large areas of sun facing glass on clear sky days.
Flying Time
With the power on, a red light started flashing on the Palm-Z and pushing the throttle forward got the propeller spinning. The motor speed is stepped rather than fully proportional and oddly the rudder control does not start to work until the throttle is at step 2. This makes a controlled landing almost impossible.
With three quarters throttle set and a gentle (level) throw the Palm-Z was away. Initial flight consisted of a bobbing (climb/stall) motion suggesting that more nose-weight was needed. However, smooth flight was obtained by following the manual and reducing the throttle a little. Once the flight had settled down, increasing the throttle had the Palm-Z climbing to an unobstructed altitude. It flies at a gentle speed suited to the enclosed environment although with a pronounced node up attitude. As I had a large enough room the Palm-Z kept flying in large circles with just some throttle adjustments to keep it in the unobstructed vertical space.
Repeatedly pressing the left-trim button got the palm-Z flying straight and heading towards a wall. So, time to attempt a left turn. The slow flying speed had me expecting a leisurely turn. Instead, it banked over sharply, dropped the nose and turned quickly enough that it was past 180 degrees before I could straighten it up. The turn radius was under a metre.
Rudder operation is a case of all or nothing. The manual recommends you “strike but not hold” the rudder control during the turn. It is also suggests adding a little throttle to increase the rudder authority. The extra throttle will also help maintain height lost from the dropped nose.
So the first left turn was scary, but we were still flying. After a couple more left turns my confidence was improving, so I thought I would try a figure eight. The left turn went ok so I pushed the rudder control over to the right. The Palm-Z banked, dived, turned even sharper than when going left and before I could recover, was locked into a spiral dive that only stopped on hitting the ground. No damage was visible, although the rudder had over-ridden and stuck on the tailplane. I assumed that this had occurred during the crash.
Further flights followed in a similar pattern. A period of controlled flight that would suddenly end in a right spiral dive I could not recover from, even with full opposite rudder. Cutting the power at least led to a softer landing. Invariably, post crash inspection would reveal the rudder stuck on the tailplane and once that the tailplane has cracked next to the fin. This was repaired using the supplied self-adhesive strips.
A quick search of the Internet showed that I was not the only one suffering the right hand spiral dive problem.
To prevent the rudder over-riding the tailplane I extended it down using “Magic Tape” as shown in the photos. On further flights, the Palm-Z would still get locked into a right turn, but now it would maintain height instead of entering a spiral dive. Holding full opposite rudder would eventually break it out of the turn, heading in some random direction. A better solution, that allowed some control over heading, was to cut the throttle; wait for the Palm-Z to return to straight and level; then throttle up and continue flying.
Because the Palm-Z was turning so tightly when stuck in a right turn, I had the thought that perhaps the rudder was too powerful. The tailplane is cut to limit rudder travel but, with the tail fin skewed to reduce the prop-wash effects, the effective right turn travel is greater than the left.
To test the theory I added some layers of Magic tape to the tailplane to restrict the right rudder deflection. I used enough tape to reduce the right travel to almost zero. As expected when flown the Palm-Z could no longer turn right. Using scissors, a small slice of tape was removed. When flown this produced a large slow turn with immediate return to straight and level on releasing the rudder control. The trim/fly sequence was repeated until, with the right turn radius only slightly bigger than the left, recovery from the turn had developed a slight delay.
I was now possible to fly smooth figure 8′s back to back with the rudder control held over throughout the turn. Stress free flying at last.
Transmitter Hack
Whilst searching the web, I found a good video on YouTube that shows how to remove the spring from the throttle control. This makes for much smoother flights and stops your thumb being imprinted with the pattern from the throttle slider. There are a number of other mods that I will explore in a future post.
Conclusion
Although small and cheap, the Palm-Z cannot really be considered a toy. Even when modified to prevent a spiral dive, it is too fragile and requires a degree of concentration to keep it flying within all but the largest of rooms, that puts it beyond the wit of most children. The box suggests an age range of 8+ which seems about right.
With it’s biggest flying challenge being a smooth figure eight, it’s long term appeal is ultimately limited. There are two possible exceptions:
- It is possible to fly three Palm-Zs at once, so with to a large enough space there is scope for some friendly competition, including trying to knock your opponent out of the air.
- Being so in-expensive, there is little to be lost from modifying the basic airframe or even transferring the electronics to a new airframe. A search of the Internet shows a number of mods including adding wheels for rise-of-ground take-offs and creating a profile scale model of Polikarpov monoplane. (http://www.rcgroups.com/forums/showthread.php?t=727630)
Would I recommend the Palm-Z. Definitely! Even in the short term, you would be hard pressed to find this amount of fun for less than the £15 (including p&p) sale price. If you have always wanted to fly a remote controlled aeroplane here is the perfect entry point.
Postscript
Since this review was written I have completed the Hat-Cam that has allowed me to get some video of the Palm-Z in flight.
Just for fun – here is a collection of some of my not-so-successful moments, which at least demonstrate the palm-Z’s resilience and it’s need for a larger flying space.
Facts and Figures
Whats in the box
- Palm-Z aeroplane
- Combined infra-red transmitter and charging station
- Multi-language manual
- Wall hanging bracket
- Spare rudder
- Self adhesive repair strips.
You have to supply
- 4 x AA batteries
- Cross-head screwdriver in order to fit them.
Dimensions
- Span: 210 mm
- Length: 185 mm
- Height: 65 mm
- Weight: 6 grammes
Manufacturers Website
Available in the UK From
Posted in 2 ch, Aeroplane, Indoor, Modding, Review | No Comments »
