The Silverlit Gyrotor
June 5th, 2008 captainThe Silverlit Gyrotor is the PicooZ’s big brother. The clue to it’s unique selling point is in the name – Gyro. This is the first model in the sub £40 price range to offer a gyroscope for directional stability. It also uses 27Mhz radio rather than infra-red for control which, combined with the size, makes it suitable for flying outdoors.
The size difference between the Gyrotor and PicooZ is evident in the pictures below.
The box contains everything needed to get flying except for a 9V PP3 battery and small crosshead screwdriver necessary to fit it. There is the Gyrotor helicopter, the 27Mhz two channel controller, Mains power supply, charge controller, and the instruction manual.
Configuration
The Gyrotor is conventionally arranged with a twin blade 225mm diameter main rotor and 75mm 3 blade tail rotor. The all-up weight is 40 grammes. The EPP fuselage sits over a plastic frame housing the electronics, battery pack, main rotor motor and gearbox.
The tail boom has a decorative paper cover extending out to the rotor support. The tail motor connects to the rotor through a neat internal gear drive and is mounted above the boom on articulated supports. A lever extends from the tail rotor mount to below the tail boom with a small magnet on the end. This hovers close to a Hall Effect sensor to provide input for the direction stabilization gyroscope system. To protect the tail rotor and stiff plastic skid extends below the tail boom.
Turning the helicopter over reveals the on/off switch and charging socket recessed inside the moulded plastic undercarriage.
Above the main rotor is the huge stabilizer rotor. It’s actually bigger than the PicooZ’s main rotor. Short struts control the main rotor pitch to keep the Gyrotor flying level.
Controller
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. Above the tail rotor control is the trim knob used to keep the fuselage pointing in one direction when the tail rotor control set neutral. Trim is set rotating the knob and will have to be adjusted each time the main rotor speed changes.
The power switch has two positions: N(ormal) and R(esponsive). The manual recommends Normal for beginners and Responsive for experienced. In my experience the Normal setting didn’t provide enough control and actually made flying more frustrating. Looking at the net there seems to be a big variation in how well each Gyrotor flies “out-of-the-box”, so others may not have this problem.
The final switch on the controller is the channel selector. This should match the tab fixed to the undercarriage. In this case channel B.
Helicopter Charger
Another difference from the PicooZ is that Gyrotor is not charged from the controller. Instead you get a mains transformer and a separate charge controller. With the transformer plugged into the wall and connected to the charge controller a red LED will illuminate. Connecting the controller to the Gyrotor will illuminate a Green LED which will turn off when charging is complete.
Airspace
The manual recommends a room of about 3m x 5m x 3m. The maximum range of the transmitter is quoted as 15m. If you can - I can’t - avoid rooms with strong air currents. The Gyrotor can also be flown outdoors if there is little or no wind.
Flying
Considering myself a competent flier of the PicooZ, I was not expecting too much trouble flying the Gyrotor. That was a mistake. It took off smoothly for it’s first flight and climbed quickly towards the ceiling. I reduced the power to halt the climb and it started to drop. Increasing the power had no effect and in no time it had hit the floor. Further flights were similar and even pushing the power to maximum only slowed the descent gradually.
The problem is the huge main rotor. It has a lot of inertia and the large pitch produces a lot of drag. Further, when descending the airflow is trying to make it spin in reverse. To overcome this the motor needs to be powerful, but power comes at the expense of weight, so the motor fitted to the Gyrotor represents a compromise. It is powerful enough to fly the Gyrotor, but it can take two or three seconds before it starts accelerating. The result is that you need to anticipate more: reducing power slowly and adding it back early. By the fourth charge I had it under control, although hovering at a constant height was still difficult. Some people on the net have recommended removing the spring from the main rotor control to stop finger creep. I may try this in the future.
Directional control was more tricky. The gyro does indeed help to tame the tail and maintain a constant heading. The negative is that direction control can be sluggish, especially with the sensitivity set at normal. There are suggestions that the paper tail boom decoration blankets the tail rotor, reducing its effectiveness.
On early flights the Gyrotor adopted the classic “large right hand circle” flight pattern and the small trim knob makes accurate trimming difficult. It is not mentioned in the manual, but as for the PicooZ, inducing some anti-clockwise twist in the tail boom (viewed from the rear) helped to make straight flight and a more stable hover possible. I needed to have the tail rotor twisted 2 or 3 degrees beyond the main rotor axis. This needs to be checked before each flight as time and crashes will remove it.
My normal flying space suffers from strong air currents, so forward speed is essential to avoid being blown into walls or windows. The area is a first floor balcony in a glazed atrium with an gap around it to the ground floor. Crashes tend to be doubly bad as the collision is generally followed by fall to the floor below. During one of these crashes the tail skid broke off and the landing gear snapped. These were quickly repaired using two part Loctite All Plastics Super Glue. The undercarriage was further strengthened by binding the join with insulation tape.
Being only two channel, the Gyrotor has no control of forward flight beyond the movement you get when turning, so keeping it away from the walls was almost impossible. The net has numerous examples of Gyrotors with wood screws sticking out the front to induce some forward motion. I taped some screws to the nose which did improve things, but the extra weight reduced the flight time meaning it was not a long term solution.
I had hoped to fly the Gyrotor outside, but considering the lack of forward speed, the wind was always to strong and I didn’t want to go chasing it all over the field.
Modding the Gyrotor
There’s a good forum thread at RCgroups.com dealing with the Gyrotor. From here I was able to get some clues on improving my Gyrotor’s handling. (Try them at your own risk).
The first mods didn’t require any major surgery.
- The forum thread reminded me that twisting the tailboom would stop the right hand circling. To stop the boom un-twisting with time and crashes, I warmed it with a hot air gun and then held the twist in place while it cooled.
- I didn’t want to risk setting the paper tail boom decoration on fire with the hot air gun, so I removed it. I hoped this would also remove any blanketing of the tail rotor and improve it’s effectiveness.
- The tail skid broke off again, so I cut a fin from a fruit corner yogurt pot and bonded it to the boom forward of tail rotor.
The other mods were more drastic.
Rotor Head
Some owners have reported excess play in the main rotor mount causing erratic flight behaviour. To test this, hold the main rotor stem stationary with one hand and then with the other, try to move a tip of the main rotor blade up and down. If there is any slack in the system, then this mod may help.
The main rotor is clamped on it’s hinge by a small plastic moulding. Four screws come up through the rotor into posts on the clamp. If these posts are too long, they bottom out against the rotor leaving slack space around the hinge. This leads to the erratic flight.
The solution is to remove a small amount of material from the four posts. You have to dismantle the rotor head which is achieved by popping the control struts off the main rotor and pulling out the stabilizer hinge pin.
Turn the Gyrotor over and using a small cross head screwdriver (or a 2mm flat blade) remove the four screws. Pulling the main rotor towards the fuselage will pop out the clamp moulding.
Remove a small amount of material from the posts with a fine file. Half a millimeter should be plenty.
Reassemble the main rotor and clamp on it’s hinge. Tighten the four screws until they pinch. Keep them even by tightening across one diagonal and then the other. Check that the main rotor is free to rotate on its hinge. If it is tight or sticking turn all four screws back an eighth of a turn and try again. If, with the screws tight, there is still slack in the system you will need to remove some more material from the posts.
Replace the stabilizer rotor. Don’t push the hinge pin right in or the stabilizer will not move freely.
Finally, reconnect the struts to the main rotor.
Fuselage
The second major mod involves hollowing out the front of the fuselage so that the battery can be moved forward. This works the same as adding the sticky aluminium pads to the front of the PicooZ. The shift in the centre of gravity leads to a slow continuous forward flight but, because no extra weight has been added, there is no reduction in flying time.
The first task is to separate the fuselage halves from the underlying structure. Remove the nose protector (if attached) and then, using a sharp knife, cut around the vertical joint between the two halves. Don’t try to cut through all in one go, but make a number of shallower cuts instead. This will help prevent damage to the internal working. At no point is the fuselage thicker than 4mm so don’t cut any deeper than that.
Once you have cut right around gently pull apart the fuselage halves at their top. Some of the wiring is stuck to one half of the fuselage (the starboard side for me), so try to pull the other side away and leave that one in place.
As you can see above the battery pack is supported below the motor on two plastic arms; fixed using paper tape. The three wires running from the circuit board connect to the LED under the nose. Unstick the wires and pull away the LED. The second fuselage half can now be removed.
The picture above shows the bare frame. A second snap of undercarriage is visible.
The battery compartment is extended forward by cutting away about 4mm of material. Don’t try to go too far or you will cut through the outer skin. The image below shows the before and after.
Pull the battery pack off it’s supports and then tape the ends of the prongs together with insulation tape. These will act as spring pushing the battery pack into the nose. As the LED can no longer fit in the nose, trial fit the battery pack and cut small notches in the fuselage halves just to it’s rear.
Reassemble one side of the fuselage to the frame. Place the battery pack in it’s bay and press the LED into it’s notch. Ensure that the wires are not fowling on the gears or in danger of shorting the PCB.
Refit the second fuselage half and tape the two sides together. You could glue the two sides together latter if desired. Finally, replace the nose protector and you are ready to fly.
Flying – take 2
With the modifications in place, the flight behaviour was definitely improved. Maybe not a startling improvement, but at least worthwhile. Flight seemed a little smoother and it was now possible to steer away from the walls. Unfortunately towards the end of the flight, an air current up the stairwell pushed the Gyrotor into a large plant. The tail rotor got tangled in some leaves, followed by a fall over the balcony edge to the floor below.
In the crash, the tail rotor mount was mangled and the hall effect magnet was lost, bringing further testing to an end before I got a chance to try it outside.
Conclusion
The Gyrotor is a mixed bag. There seems to be a huge variation in how well they fly out-of-the-box. If you get a good one then your initial experience will also be good. conversely, if you get a bad one, you’re going to be disappointed. However, all is not lost. Provided you don’t mind some knife work, you can mod it back to health.
For those with experience of the PicooZ, the main rotor’s time delay will take a little getting used to, but if you are planning to move onto even larger machines, it will be good practice.
Before making the modifications, I probably wouldn’t have recommended the Gyrotor, as costing two or three times more than the PicooZ, the fun per buck wasn’t worth it. Since then, I’m more inclined to stick with it and have ordered a replacement airframe (without the controller) from Silverlit’s online store. This only costs about 60% of the full package, although delivery is quoted as 4 to 6 weeks. With summer approaching, I may even get a chance to try it outside.
Finally, if you like the idea of the Gyrotor then give it a go. If you already have a two channel helicopter like the PicooZ, you might be better off jumping to the next level with a three channel machine.
Postscript
After 6 weeks of waiting nothing had arrived and I had received no correspondence, so I sent an email to check progress. No response. After 8 weeks I send another email with the tag line that I would be contacting VISA if I didn’t get a response. Still nothing. I contacted VISA, they sent me a form, I filled it in and sent it back. Within two weeks the money had been credited back to my account. Two days later a new Gyrotor arrives via express air mail from Hong Kong. It looks like a poke from VISA did the trick.
The replacement Gyrotor flys much better right out of the box. It is easier to trim and hover, so I have no plans to mod it. After a period flying the PicooZ and Altas, I really appreciate the directional stability afforded by the tail gyro. It still has some issues. In the middle of a flight, just when I’m wondering if I can keep it airborne for an entire charge, the motor will cough as if it has momentarily cut out and then it gets stuck in a right hand turn. I assume the thermal cutout has kicked in and reset the gyro. The only option is to land and turn it off and on again
I have tried flying the Gyrotor outside, but found that it was carried downwind in even the lightest breeze and it tended to weathercock with every bit of turbulence.
In summary, my experience with the Gyrotor has improved and I would recommend it to someone who has plenty of indoor space to fly in. For now it is the machine I’m flying the most, but there is a three channel helicopter under my desk waiting to be flown as soon as I finish the next review.
Facts and Figures
Whats in the box
- Gyrotor helicopter
- 27Mhz radio transmitter
- Charge Controller
- Nose protector / weight
- Manual
You have to supply
- 1 x 9V PP3 batteries
- Cross-head screwdriver.
Dimensions
- Main rotor diameter: 225 mm
- Fuselage length: 240 mm (Excluding tail rotor)
- Height: 110 mm
- Weight: 40 grammes
