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       OS 1.20AX
the Next Generation Glow Engine

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Displacement: 1.20 cu in (20 cc)
Bore: 1.197 in (30.4 mm)
Stroke: 1.083 in (27.5 mm)
Practical rpm range:: 1800-9500
Power Output: 3.1 hp @ 9000 rpm
Weight: 21 oz (650 g)
Includes: #8 glow plug, 70D dual-needle carburetor, E-5020 Power Box™ muffler w/two adapters
Recommended Props: 14 x 10 APC, 15 x 6 APC

OS is probably considered the Premier engine maker in R/C modeling. They offer a good variety of engines to cover just about any application. One of the nitches they had a good hold on was the big Pattern Airplane market (IE:1.20 size). While there was stiff competition to fill the Pattern cowlings, OS prevailed in the two strokes and YS claimed domination in the four strokes. Today, Pattern Flying is predominantly four strokes and OS kept pace with several premier four stroke engines. OS was the first to offer a genuine direct drive super-charged engine then followed by a genuine electronic fuel injected four stroker. YS created a Pattern Beast called the Dingo 140, a "real" direct fuel injected engine. Whew, what a beast this engine is! It's taken home first-place in virtually every class. The two stroke powered Pattern Ships couldn't hold a match to the four strokes performance in smooth predictable power.  
 
This brought OS engineers back to the drawing board. While OS has a great line-up of four strokers and very competitive with them, OS apparently wanted to keep their largest two stroke engine alive and well. This mandated some re-thinking of the role the 1.20 two stroke would play in future applications. I doubt that Pattern Planes will ever see two strokes in serious competition ever again. However, large sport and 3D airplanes are gaining momentum. This is probably where OS intended their new 1.20 AX Series engines to make itself home. This Next Generation (AX) two stroker made some major changes to generate smooth linear power throughout the entire RPM range. The AX is much more than a re-hash of an existing engine, but a whole new philosophy on how a two stroke should generate energy. The 1.20 AX is a long stroke engine (by comparison) and its effective stroke is the longest on the market today. The effective stroke is the portion of the stroke that starts at Top Dead Center and traverses all the way down to the top of the exhaust port. This is where the combustion generates its power (torque).  The AX maximized this. It also has new porting specifically designed to transfer fuel & air rapidly to the cylinder with minimal invasion of the effective stroke. The crankcase volume has been reduced to  maximize fuel transfer velocity as well. This kept the physical dimensions small, thus the AX is lighter weight and can fit where a .91 currently resides. The cooling fins were re-designed to get maximum effective cooling with minimal surface area. And then there's the carb. The AX carb went through several engineering changes to get optimum air/fuel mixture regardless of throttle position. This in itself was a major improvement for two strokes in general. Finally, there's the exhaust system. The AX optimized the volume (area) to provide linear power instead of topend power, it's called the POWER BOX. These changes through the course of countless R&D funds and 1000's of hours of prototype testing, the 1.20 AX has immerged as the most efficient two stroke engine in its class, ever.

Will it replace the four stroke? Not even in your wildest dreams. However it DOES provide a cost effective alternative. Plus you get the smoothest power-band ever developed in two stroke. There's a lot to be said for that. 

Kudos to OS.

 

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