It is, of course, the Keyence Engager GS III which is sold primarily as a toy in its native Japan, but which is now being imported in to Europe by the German company Intertronics.
This unique flying machine is part of an amazing range of high technology devices manufactured by Keyence. These include a miniature single rotor 'conventional' helicopter ( which will be reviewed here later this year ), a tiny tandem rotor machine that looks like a Chinook and the predecessor to the Engager that has mechanical rather than piezo gyros.
One other fascinating product that I saw demonstrated in a Tokyo toy shop a few years ago is an electrically driven wheel which is steered by a couple of propellers mounted either side of the hub.
The propellers blow it over in to a bank and hence cause it to turn..
Although the electronics in the Keyence flying machines are very advanced, they all use simple 'cooking' ferrite magnet motors and rely on clever, low weight structural and control system design to give acceptable performance.
The Engager uses four '280' size motors with single stage reduction gearboxes driving 330 mm diameter rotors which are rigidly mounted on to the output shaft. The rotors are attached to the four corners of the expanded polystyrene body. One rotor is in the front, another at the rear and the remaining two are either side. The fore and aft rotors rotate in the opposite direction to those at the sides and this is achieved by inverting two of the gearboxes.
The rotor blades, which are thin, undercambered foam mouldings with an aluminised plastic top covering, are handed to accommodate the different rotation directions.
In the centre of the body is a moulding to hold the on board battery ( 6 Sanyo 500 ARs ) and the electronics module.
On board electronics includes a receiver, three piezo gyros, a microcontroller with the control logic and four speed controllers, all in a sandwich of two 60mm square printed circuit boards weighing only 50g.
Control of the Engager is by differential speed of the rotors. Forwards and backwards is achieved by varying the relative speed of the fore and aft rotors. Sideways movement similarly varies the left and right rotors. Height is controlled by speeding up or slowing down all the rotors together. Yaw is possible because of the opposite rotation of the two sets of rotors. Speeding up the clockwise rotors and slowing the other pair gives anticlockwise yaw and vice versa.
The piezo gyros in the control system keep the Engager stable in all three axes and provide damping which allow it to be flown in confined spaces.
Assembly is minimal which was fortunate because the manual was in Japanese. It required only the attachment of the blades to the individual rotor heads, using double sided foam pads and a neat plastic clamp, and then fitting the rotors on to the gearbox shafts. The battery connectors were unusual and I did not have anything to fit them so they were replaced by Powerpoles ( Sermos connectors ). The electronics module requires the attachment of a vacuum formed clear plastic cover with four tiny screws and it then clips in to a plastic frame in the centre of the body. Care is needed to make sure that the clip is firmly attached. If the module moves in flight it will upset the gyros and the stability is lost. I also had to repair the expanded polystyrene body which had been cracked by handling before I received the model. Odourless, foam friendly cyano made short work of this.
At this point the Engager was ready to go, but I was not ! My problem was that the transmitter ( which looks just like a Futaba low cost 4 channel Tx ) is set up for mode 1 ( throttle on the right ) which is the standard heli mode in Japan. I have always flown mode 1 with fixed wing models but when I learned to fly helicopters I could only find instructors on mode 2 so that was the mode I adopted. I went back to my PC simulator for a week with it set to Mode 1 and got to the point where I could hover reasonably well and then decided it was time to try the Engager.
There is no on-off switch on the Engager so the start up procedure is to connect the on board battery and fit it in to the centre of the body. The electronics module is then clipped in place over the battery. You next stand clear and switch on the transmitter. An LED lights to show that the signal is being received and about ten seconds later the rotors give a quick burst of power showing that it is ready to go. Slowly opening the throttle starts the rotors and the Engager will lift off at about half stick. With a fully charged battery the model is quite lively and tends to hop in to the air and then bounce down again. This is quite easily controlled if you are on the right mode but I found it extremely difficult on the wrong one ! I will spare you the gory details, suffice to say that I am not going to be successful at Mode 1 helicopter or Engager flying. Fortunately, Keyence recognise that the blades are expendable and provide lots of spares. I also eventually remembered that when the model is upside down and thrashing itself to death, the way to stop it is to turn off the transmitter. The model survived all this undeserved mayhem remarkably well. Apart from the blades and a few more cracks in the body, no real damage was done. It was obvious, though, that something was going to have to be done about the transmitter mode.
The electronics module has a switch to change modes, however this only moves rudder ( yaw ) from the left hand stick to the right, giving reverse Mode 2. This does not help ! It was, therefore, necessary to be more radical. The Engager transmitter is a simple modern digital ppm device with all the sticks giving voltage inputs to the encoder chip. I therefore unsoldered and exchanged the leads from the throttle and elevator stick potentiometers on the main circuit board. The throttle ratchet and the centring spring were also exchanged and 'bingo' I had a Mode 2 transmitter. If the Engager proves popular outside Japan, I am sure that the importer or the manufacturer would carry out he modification.
With the transmitter on a familiar mode the Engager proved a delight to fly. It lifts off in to a very stable hover and there is sufficient power to climb well out of ground effect. It is possible to fly in very confined spaces, most of my test flying was in my living room. I also flew it in front of the audience at the BEFA technical workshop on a very small stage, in between a table and an overhead projector. The only thing that requires particular care is a tendency to pilot induced oscillation which needs careful anticipation to damp it down. Once you are familiar with the machine this is not a problem. I have also flown the model outdoors on a calm day and I was able to do very neat pirouettes with no tendency to drift or change altitude in spite of the changes in rotor speed which are necessary to produce the yaw. Forward flight is a bit strange, the model initially accelerates but quickly reaches a maximum speed and is reluctant to go faster. It is not clear if this is a control system or an aerodynamic effect. It does mean, however, that the model is unlikely to get away from you as often tends to happen with a conventional helicopter when you are learning to fly. Flight time with the on board battery is around three minutes. I made up an umbilical lead to fly it from a ground based battery and this gives about ten minutes with a 1700 SCRC pack. I initially tried a 7 cell pack but the model was almost uncontrollable with the reduced weight and the extra power. With a 6 cell pack it is fine.
The Engager is certainly easier to fly than a conventional helicopter. It is not so easy, however, that junior could expect to be proficient by Christmas lunchtime and it is likely that there would be some tears along the way unless he or she had careful coaching. For a grown up it is tremendous fun but you really need access to a large indoor hall to get the most out of it. Outside it is badly affected by the wind and there will not be many days you could fly it in the open. The box says that the body and rotors are expendable and I have to agree ! Spares are available, however, and the motor / gearbox units have proven to be very rugged.
Overall, this has been a great experience and an opportunity to fly something very different. Now, if I get four geared Astro 05s and three CSM gyros ........
The Engager is available from:
INTERTRONICS
Gregor Hyrenbach
Rotebuhlstr. 44
D-70178 Stuttgart
Germany
Tel. ( 49 ) 0711 612976
Fax ( 49 ) 0172 7131059
http://www.INTERTRONICS.de
Please tell them EFI sent you.
(Written by: Mike Goulette)
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