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Polini Thor 202 is born from the experience acquired with Thor 200 and from the demand of the market of a powerful and lighter engine that at the same time can grant more thermal stability. The solution adopted by Polini’s technicians to achieve this goal is to use the liquid cooling system, technology that have been tested for many years on Thor 250.
The new Thor 202 stands out engines for its extraordinary weight reduction. It is 1,6 kg lighter compared to Thor 200HF including the cooling system too and it is 4hp more powerful with optimized torque curve above all at low rpm, thus granting lower consumption and more comfort when flying besides an exceptional thermic stability.
Great attention has been dedicated to the aesthetic and aerodynamic features, that have driven to the production of a brand new airbox with a modern design and small dimensions. Even the cylinder has been completely re-designed to be highly performing to grant the maximum performance. An exclusive, reliable and long-lasting product, to grant longer life to the engine and increasing the TBO (time between overhaul) up to 400 hours.
Following the technical details:
The cylinder The core of the engine is the cylinder that has been designed and manufactured with last generation details. The real displacement is 205cc with 66mm bore and 60mm stroke. The cylinder has 5 transfers to give precise performance and fast output able to offer more than 90kg of static trust with 130cm propeller installed. The muffler 2 stroke engines are in Polini’s DNA. Thanks to experience acquired by the factory during years of studies and researches, it has been possible to manufacture a brand new exhaust system.
The new expansion is light and with compact size. Thanks to the hard work on the tests, it has been possible to find the perfect union between expansion and gas flows: the result is a muffler that assures a stable and progressive power output at all the rpm. It is installed to the engine with a granted system that assures free movements and reduced vibrations.
Another improvement comes from the connection that it’s positioned to one third of the muffler itself and it is made of a spherical coupling that allows free movements and extends the life of the muffler.
The new Thor 202 is available with Dell’Orto carburetor. VHST 28mm Dell’Orto carburetor has allowed to make the carburetion setting, granting flowing performance. The main features are: low consumption thanks to the efficient Venturi effect, 2,4 liters/h at 5000rpm, which corresponds to 30kg of static trust, average value at flat flight with a 130cm propeller (evidence on the standard setting at sea level and improvable during competitions).
The unique design makes it less sensible to environmental changes connected to atmospheric pressure, humidity and air pressure, granting more stability to latitude/longitude and height variations and minimize the setting sections. This carburetor can be equipped with Polini throttle control too to activate the throttle when pilot is ready to fly. Thanks to these advantages and different settings options, Dell’orto carburetor will satisfy the needs of all the pilots thanks to its high precision, fluidity and power output, together with vry low fuel consumptions.
The new air filter is the result of a deep fluid dynamic study that has the aim to optimize the air speed inside it to grant the perfect pressure to feed the carburetor at every rpm. By reproducing a S circuit that stabilizes the turbulences, the new filter lets a linear, sweet and constant output. It is possible to open and check it; inside there is a supporting frame for its filtering carpet made of polyurethane foam with open cells of 30 PPI (holes per inch): this supporting frame has been designed to have a fixing able to prevent the carpet from moving or collapsing on it. Furthermore the filter cage can be opened in a half through two screws to be easier to replace it during standard servicing.
The new filter has a modern design and it is more compact compared to the previous versions: thus it is 45mm closer to the engine, reducing the aerodynamic resistance when flying. Cooling system and water pump
The cooling is granted by a 16-component compact radiator with reduced size of 300x170mm and it has been designed to avoid using the expansion tank. The cap is provided with a 1,4 bar valve to let the system self-regulate the expansion of the liquid inside it without weighting on other parts. Tank and its parts omission contributes to aerodynamic and to the reduction of the whole weight. With a great attention to the look, the pipes chosen are made of blue silicon that, besides having and attractive color, they grant longer life.
The engine is equipped with reed valve with direct intake in the engine crankcase. The reed valve, designed by Polini R&D department, has been conceived to optimize the performance. This result can be achieved thanks to the use of 6 carbon fiber reeds with calibrated elasticity to react uniformly at all RPM.
Thor 202 crankcases are die cast in aluminum with high silicon content: thanks to this alloy and to the production process during all the phases (starting from the foundry, passing through the painting, to the mechanical working on sophisticated CNC machines), it is possible to achieve stable and long lasting mechanical performance matched to a reduced weight. The design of the crankcase has been optimized to be complete and reinforced where more stressed, increasing the TBO up to 400 hours.
The choose of the best steels and thermic treatment together with a perfect centering, eliminates vibrations due to unbalancing that during the time should drive to premature worn or structural failure. Thanks to the CNC machines and to the use of measuring tools of last generation, the dimensions stay inside pre-arranged tolerances. Moreover the bearings are of very high quality and are placed on the coil and crankcase.
Countershaft, gear and clutch
In the front crankcase there is the housing of the centrifugal clutch system, the mechanical reduction and the balancing countershaft, all in oil bath. The centrifugal clutch allows the propeller to be static when the engine is to minimum rpm and maximizes the safety for the pilot in the pre-flight stages.
The mechanical gear has helicoidal teeth: this system inverts the revolution way of the propeller respect to the crankshaft, softening the overturning torque. The balancing shaft reduces the vibrations coming from the unbalancing generated by the piston swinging that, passing through the BDC and TDC, moves the mass at every single rotation circle of the engine, thus granting the maximum flying comfort.
Thor 202 is equipped with an inductive electronic ignition: more compact and light compared to the model installed on Thor 200 HF it lets the reduction of the engine distance of 16mm, making the engine more compact.
Thor 202 is equipped with the latest version of the well known Flash starter, system that grants an easy engine starter. The critical points of the last version of the flash starter have been reinforced, improved the centering to extend its life. An ergonomic handle lets a safer and stable grip during the starting.
Polini Motori has decided to maintain the same fixing points on all Thor engines. A choice for the manufacturers and pilots benefit. Manufacturers may produce a frame that can house the entire range of Thor engines, thus reducing significantly production costs and timing.
Pilots can replace the Thor engine without replacing or modifying the frame. Thor 202 is sold together with all the parts necessary to install it, already assembled and ready to be assembled on the frame very easily.
|Polini Engine||2 stroke mono-cylinder|
|Bore for stroke||66 x 60|
|*Max trust||90 Kg with Ø 130 cm propeller|
|Cylinder||Aluminum with Gilnisil coating|
|Piston||Two chromium plated rings mm 1|
|Intake||Reed valve in the crankcase|
|Carburetor||Dell’Orto VHST carburetor|
|Air filter||Air box r|
|Ignition||Electronic T.C.I. fixed inductive timing|
|Spark plug hood||5 K Ω resistance|
|**Fuel type||E5 petrol or LL AV GAS-al with 2,5% synthetic oil 100%|
|*Consumption||2,4 Lh at 30 Kg of static trust|
|Gear reduction unit||Helical teeth in oil bath with 2,8 reduction ratio|
|Clutch||Centrifugal in oil bath|
|Muffler||Expansion with oval silencer|
|Engine weight||From 16,8 Kg.|