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Turbine Engine Theory
Turboshaft Design

The turboshaft turbine engine operates in exactly the same manner as the turbine engine described in the turbine theory page. The basic difference comes down to a gear set inside the turbine which is driven by the turbine wheel and mechanically transfers the engine power to the clutchbell. Our JAKADOFSKY turbines have a 5.1:1 internal gear reduction which produces a new perfect output RPM range for use in model helicopters and industrial UAV applications.


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JAKADOFSKY's experience with full scale engines lead to the R turboshaft turbine which back when it was released, was already years ahead in terms of electronic control and easy of use.

The classical turboshaft design is an adaption of a turbojet engine. Essentially in a jet aircraft, the exhaust in the tail cone is accelerated and the thrust is used to propel the aircraft forward. Turboshaft engines use two fundamental designs to turn a drive shaft that interfaces with a transmission on the airframe.

Free Turbine Wheel Design

Most commonly used in full scale turbine engines is the 'Free' turbine wheel which is normally located after the compressor turbine wheel and is driven by the engine exhaust. This design commonly uses two separate drive shafts which are not connected. This separation keeps the engine and tranmission in two discrete sections making the engine more flexible to be installed in different airframes. This inherently makes the turbine engine longer and creates a challenge for the exhaust system as it is directed outwards, commonly upwards or to both sides, just past the free turbine wheel.

Internal Gearbox Design

Turbine engines which use an internal gearbox are generally designed for smaller applications or for a particular purpose. The JAKADOFSKY turbines fall into this category where the gear reduction is internal to the engine, is maintenance-free and guaranteed for life. By internalizing the gear reduction, the turbine is directly connected to the output shaft which improves on the general design by greatly reducing throttle related delays in supplying power to the airframe. In the turbine cycle, as energy is extracted and transmitted to the mechanics, the residual exhaust velocity is reduced as it is exhausted directly out the back of the turbine. Exhaust systems are simpler and can be customized to fit the particular model or airframe.