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The story

the first minicopter model, the Joker 1, was the first modern electric helicopter produced in carbon/aluminium technic and so still enjoys great popularity. Over time, many requests were brought to my attention, to create a modernized mechanics of the Joker 1. The concept of two-stage gear transmission with belt-driven tail has proved to be extremely reliable. So it made sense to create a special 3D helicopter, of which the performance will be greater than that of the Joker.

The construction began quietly. It is often better to work on a special project like this when not so many people know about it. So some very intensive testing was possible for several months, during which many small changes have been included into the design. Such a new model requires a testing period, during which improvements can be made systematically.

Why "Diabolo"?

A diabolo is a toy with which you can show tricks after some practice, like a 3D heli. A diabolo is however also a rifle-bullet for target shooting, which can be equated with speed flying. When the first canopy was completed, a friend was present at the model aircraft field and he has a spontaneous declared a third meaning when he looked at this new design: "That's the devil!" Anyone who looks at the canopy closely will certainly discover what he means. This detail is to prevent tearing of the canopy in the area of the aileron servos from frequent removal. This newly designed shape still matches the Joker family perfectly! However, it is clearly a few inches higher, and a bit narrower, making it much more aerodynamic in flight.


When you see the model fly for the first time as an experienced pilot, the thick tail boom immediately catches your eye. This allows it to be seen at great distances or during fast maneuvers extremely well, and gives the diabolo almost the appearance of a model with a fuselage. Through the very light tail design and with a belt drive, very high pirouette rates are achieved. Most striking however is the enormous flexibility of the Diabolo. It can be flown with a slow turning main rotor, or flown with a very high rotor speed at the maximum limits.

Technical data
  • Rotor diameter: 1,56 to 1,68m (Blade length:690-750mm)
  • Weight with 12s/4500: 4,8-5,2 kg
  • 2-stage gear, helical spur gear for motors with 40-45 mm stator diameter
  • Gear ratio 1st stage: 1:3,1 to 1:4,13
  • Gear ratio 2nd stage: 1: 3,17
  • Belt driven tail rotor
  • Tail gear ratio 1,5:1
  • Tail rotor diameter: 290-300 mm
  • Length with canopy: 1,38 m
  • Length without canopy: 1,27 m
  • Height: 39 cm
  • Landing gear width: 22 cm
  • Tail boom diameter: 30 mm
  • Hanging battery for COG
  • Battery tray: 68(74)mm high, 64 mm width
  • Automatic belt tension over oil-pressure shock absorbers with adjustable spring rate

 Pinion calculation: It is very difficult to find as manufacturer the best pinion for a customer, because there are many factors we do not know. A good calculator to find the individually best pinion you find here: Pinion calculator

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If you would like to be part of this new generation of helicopters, be sure to pre-order yours today!


Diabolo in der Heli4Fun                   RC-Heli-Action