Evolution Power System, The

Model Airplane News, Nov 2003 by Gierke, Dave

The Evolution Power System Way back in the '20s and early '3Os, if you wanted an engine for your free-flight model airplane, it had to be machined and required a casting kit and a set of drawings. In 1934, Bill Brown manufactured the first commercially available RC engine in the United States; it was the Brown junior .60 (Model B). Before aspiring modelers could run it successfully, they had to learn all about their new engine and what it involved: fuel tank, needle valve, gasoline, spark plug, breaker points, condenser, advance lever, battery, switch, etc. In 1947, Ray Arden introduced the glow plug; this eliminated the cumbersome spark-ignition system and greatly simplified engine operation.

During the next 20 years, many refinements found their way into model 2-stroke engines, primarily in design and materials. In the late '60s, the first ABC engines appeared in hobby shops. They offered several advantages over conventional designs, but none was more important to sport modelers than the short time required for break-in-less than half an hour, in some cases. Engines continue to become easier to operate, and a new engine-the Evolution Trainer Power System-now represents another paradigm shift, and it supersedes all the engines that came before it.

Produced and distributed by Horizon Hobby Inc., the Evolution Power System consists of a .455ci 2-stroke Alpha engine, a muffler, a 3-blade "training" propeller, a spinner and a flywheel for smooth running and easy starting.

Designed expressly for newcomers, the system incorporates several unique features that help to ensure immediate success.

* Every engine is test-run and broken in at the factory.

* The high- and low-speed needle valves have a limited adjustment range, and that minimizes the chance of error but allows fine-tuning to suit variations in altitude and/or weather conditions.

* The needle valves are adjusted for maximum wide-open throttle (WOT) and idle performance at the factory.

* The Evolution Power System comes with a reader-friendly users' manual that contains everything a beginner needs to know. Of particular interest is the description of how to set the high- and low-speed needle valves-impressive. In addition to installation, starting and adjustment instructions, the manual provides a parts list, a troubleshooting guide, a maintenance section and warranty information.

ENGINE CONSTRUCTION

Before I ran the Evolution, I disassembled it to check its design and the methods and materials used in its construction. The bead-blasted, die-cast crankcase has a unique arrangement of cooling fins that wrap around the crankcase from below the exhaust stack at the front to just below the cylinder head at the rear; this very distinctive look certainly won't be mistaken for any other design!

The Evolution .46 features a front intake and a side exhaust. The crankshaft is supported by two ball bearings, and the piston and cylinder sleeve are of the lapped ABC type. Cylinder-sleeve porting consists of two Schnuerle transfer ports and a single boost port. The aluminum-bar-stock connecting rod is bronze bushed at both ends and has the appropriate drilled lubricating holes. The hardened and ground crankpin is pressed into the offset portion of the massive counterbalance, while the bearing journals and nose threads have been case hardened and the bearing journals ground to final size.

The amply finned cylinder head has a hemispherical combustion chamber with an angled squish band; it has a special, long-snout "Super Plug" that purportedly prevents the engine from flaming out when it transitions from idle to WOT. The snout is designed to direct the fuel/air mixture away from the platinumalloy wire element; in other words, it works like an idle-bar plug. The new Super Plug is available from Hangar 9 (item no. HAN 3006) and is worth trying in any engine that displays throttle and transition-related problems. [When you remove the glow-plug heat connector (battery), that the plug is slanted rearward also provides a degree of safety in helping you to avoid the spinning propeller.]

The 2-needle-valve fuel-metering carburetor incorporates a remote high-speed needle (mounted on the rear cover) with a press-fit axial pin that limits its rotation to approximately one turn (360 degrees). The low-speed needle valve has a similarly pressed-in pin that limits its rotation to about 1/4 turn (90 degrees). Both needle valves are close to the required mixture setting as they come from the manufacturer. Although I had reservations about the limited range of the available needle-valve adjustment, the engine performed flawlessly throughout my trials. One full turn of the high-speed needle valve proved to be more than enough to adjust the air/fuel mixture.

Immediately below the carburetor cinch bar, the crankcase is fitted with an O-ring that eliminates any chance of the air leaks that are sometimes associated with other sealing methods; this great idea is catching on throughout the industry. The 2-ounce steel flywheel is pressed onto the aluminum prop driver's outer diameter; weight added to the crankshaft helps provide rotational momentum to the propeller; this helps to smooth engine operation and assists with starting.