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Joker Helicopters - Joker Acrobat

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Joker Acrobat

Master data


Accessories	[ Joker Acrobat ]

A fully Aerobatic Helicopter for .91 engines(15ccm)
Main rotor diameter: 1560 mm
Tail rotor diameter: 290 mm
Weight without fuel: 4,1 - 4,4 kg (9 -93/4 lbs)

The Power

[ The Power ]

Options are available to suit any 91 size engine (OS, Webra, Yamada).
New high volume flow diagonal cooling fan which is, light, efficient and independent of engine running direction. The whole engine surface will be cooled, so no extreme heatsink is needed. The shroud is made from fibreglass.
Robust two-stage gear with highest possible efficiency. Toothed belt drive with stabilization/tensioning rollers on the first stage, the second stage has a 15 mm wide gear wheel. Tailrotor drive comes off the first stage for minimal power losses. Gear ratios of 7,75:1 or 8,15:1 are available.
Extensive use of CNC bearing blocks allows for very tight tolerances to be maintained throughout the power transmission train
The main rotor can be either right or left rotation (with a special reversed motor).
10mm- strong autorotation free-wheel unit in the first stage for constant drive tailrotor during AR. The symmetrical free-wheel unit may be used for both left and right hand blade rotation (in combination with a suitable engine). A second AR clutch is optionally available for stationary tailrotor in AR.
Tail drive is taken from the first stage pinion shaft by means of a smooth running toothed belt, employing metal belt drive gear wheels and stabilization rollers on both sides. Tail gear ratio is 4,79:1. The tailboom is not anodized on the inside to avoid any interference.
The transmission is completely enclosed by the canopy and is very quiet.
Because of the large distance between the bearing blocks on the main shaft and by using flanged bearings (which are very easy to change) there is very strong anti-twisting support to the rotor with relation to the frames.
500 ml fuel tank which is easy to mount and to remove, there is provision for mounting a header tank in front of the main tank.
High volume stainless steel muffler with flexible mounting to the lower frame (optional), a tuned pipe is will also fit.
Provision is made for fitting a governor magnet into the clutch.

Control & Electronics

[ Control & Electronics ]

Joker Acrobat utilizes a central position of the receiver for maximum protection and best possible cable routing efficiency using a special console in the upper frame.
Swash-plate servos with push-pull linkage-bellcranks to the swashplate, swashplate antirotation by means of a CNC restrainer block between the frame plates.
Short, straight linkages for precision control
Throttle servo is in the lower frame block and allows for push-pull linkage. There is provision for the mounting of a mixture control servo if required.
Boom mounted tailrotor servo with carbon fibre pushrod for maximum tailrotor control
Gyro mounting platform on the tailboom
Receiver battery mount on a console in front of the shroud.

Joker Acrobat Tail system

[ Tail system ]

Light weight
Simple structure
Easy service
High precision
Mounting on right or left side (depending on main rotor direction)
CF-vertical stabilizer with well formed fin
CF-horizontal tail unit
Rigid hub
Aluminium blade grips with each one containing two radial and one axial thrust bearings
Integrated propeller moment weights for reduced servo force.
K&S blades for precise control

Joker Acrobat frame

[ The frame ]

High strength, light weight, technically optimized construction yielding a tortionally stiff frame system made from 2.0 mm CF
Side profiles have cutouts for weight reduction.
Skid type landing gear from polyamide with aluminium tube skids
Carrier arms for the shroud and the receiver battery
Robust anodized aluminium tailboom with 25 mm diameter, not anodized on the inner side.
CF-tailboom support

Who should fly the Joker Acrobat

Beginners and casual fliers(robust, good hovering stability, smooth motor sound from big silencer and low rpm). Beginners should use half throttle and reduced control throws.
Expert fliers (low attrition, long life of all components)
3d-fliers (extreme power/weight ratio, high response, precision, slop and friction free control systems)
FAI-competition fliers (low C of G for smooth hovering, low air resistance and good aerodynamics for high speed flight, low model weight for large precision manoeuvres )