TURBOPROP MODEL JET ENGINES ARE TRUE TURBINES THAT CAN POWER JET MODEL AIRCRAFT.
This photo shows us how the modern 2-stage RC plane turbine looks on the inside. The term 2-stage is important. It refers to the fact that a second turbine is used to power the gear reduction box. When a single stage jet turbine is used, the gearbox is coupled directly to the turbine shaft.
In this set-up a lot of energy is still exiting the nozzle as thrust. This results in an inefficient design and unwanted forces exiting the rc airplane as thrust.
If we look at the Wren design, the first part of the turbine is the first stage of the engine. This is a standard R C jet engine, as described in "RC Jet Engines Simplified" Click here for details.
At the exit of this stage, the nozzle is replaced by a cone shaped connector, the contains the second stage compressor. It is this compressor, that is connected to the gear reduction gearbox. Note that there is no mechanical connection, between these 2 stages, just the hot, compressed gases from the first stage.
The exhaust gases from this stage are exited sideways, through the exhaust deflectors.
The final element is the gear reduction box. Here the high RPM of the second stage compressor (usually over 150,000RPM), is reduced down to less than 15,000 RPM. This allows the use of conventional 2 or 3 bladed propellers.
The Wren 44 Turboprop replaces the model 54. Note that the air intake is at the REAR.
The engine is mounted by the flange, positioned about half-way along the body. Provision must be made to duct air to the intake, inside the fuselage. You will notice that the intake is covered by a screen.
This is a very good feature, that prevents FOD (Foreign Object Damage) Remember that this model jet engine is like a powerful vacuum cleaner, mounted in the nose of the radio controlled airplane! Any loose parts or dust will be sucked into the model jet engine-so take care!
The propeller RPM range is from 1200-9,000, with a turbine speed of 55,000-195,000 RPM. Maximum power is 5.62KW (7.5HP) at 6300 RPM. The main body dimensions are 86mm (3-3/8") diameter and the length is 326mm(12-13/16"). A unit will weigh 1759g (3lb-13oz.)
Recommended propeller sizes are from 17"x12"(2-blade) to a 21"x12"(4-bade).
Of interest is the fuel consumption of 1 fl oz per minute at idle and 5.6 fl oz per minute at full throttle.
The Tucano is a beautiful, scale model of the Brazilian airplane, that can be built as a civilian or military model.
An A.R. F. kit is available from Composite ARF, and as the name implies, the construction is of the latest in foam/fiberglass/carbon fiber technology.
The photo at left, shows the installation of a JetCental RC turbine.
This model belongs to Boli Muentes, who kindly allowed me to use these great photos.
If you click on the photos, you will visit Boli's web site, where you will find more photos and videos of this scale beauty.
As can be seen here, the Tucano is equipped with retracts, a smoke making system and a detailed cockpit.
Please note that the model jet engine and the kit, represent a substantial financial investment and if you ever get the opportunity to see it, or similar models fly, it will be well worth your time!
Finally here is a video of the Tucano, that shows all of the attributes of
this beautiful RC airplane.
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