Gas engine guide

Model Airplane News, May 2002 by Yarrish, Gerry, Jones, Melissa

When you make the transition from normal-size sport .40 models to giant-scale airplanes, the biggest difference you have to deal with is the gasoline engine. For many, these big-bore hunks of metal are a mystery because they look and operate so differently from the more familiar glow-powered (nitro) engines. In practice, however starting, running and adjusting a gasoline engine is only slightly different and no more difficult than operating any other internal combastion engine. If you can operate a chain saw or a weed trimmer, then you'll be right at home powering your next giant-scale project with a gas burner.

Gas engines are much easier to adjust and have excellent fuel efficiency; a gas engine consumes roughly 1/3 as much fuel per minute as a glow engine of the same displacement burns. Gasoline engines tolerate heat much better than glow powerplants, and they require fewer fuel-mixture adjustments to keep them happy. You might need to adjust your gasoline carburetor only once during a flying season! Though the typical gas burner produces less rpm than its glow-powered cousin, it produces more low-end torque. Thrust is produced more efficiently with that bigger, slower turning prop. Because they are heavier than nitro engines, gas engines are often used in scale airplanes that have a shorter nose moment, and their weight helps eliminate some of the lead ballast needed to balance the airplane. In giant-scale, unlimited Tournament of Champions and International Miniature Aircraft Club (IMAC) events, big-bore gas engines are the norm, and you can't argue with success!

If you're leery about using a gas engine, this guide will clear everything up.

3W Modell Motoren

The German-made 3W engines have been used in several giant-scale competitions, including the Tournament of Champions and many giant-- scale unlimited air races. 3W engines come with an electronic auto-- advance ignition system and are designed to operate at lower rpm for more thrust and less prop noise. 3W 601 (shown)-$519. Distributed by Aircraft Intl., 8 Country Meadow Dr., Colts Neck, NJ 07722; (732) 761-0997; www.aircraft-intl.com; and Cactus Aviation, 10380 E. Heritage, Tucson, AZ 85730; (520) 721-0087; www.cactusaviaton.com.

BME

Designed specifically for light overall weight while retaining excellent crankcase stiffness and crankshaft support, BME engines are known for their smooth operation and userfriendliness. Most BME engines come with the CH syncro spark-ignition system and fiber-reed induction (except the BME 44 single, which is piston ported), plus a 2-year warranty. BME 102 (shown left)-Si.149: BME 44 (shown right)-$499. BME Engines, 10101B Cordoba Ct., Waco, TX 76708; (254) 836-0835; www.bmeengine.com.

Brison Aircraft

Designed with giant-scale modelers in mind, Brison engines' enhanced power and reliability make them ideally suited to Sunday fliers, scale modelers and IMAC competitors. Available in six sizes, ranging from a 2.4ci (39.33cc) single to a big 6.4ci (104.64cc) twin cylinder, all Brison engines come standard with nicasil-lined cylinders, metal bellcranks and anodized cases. and all the crankshafts are unconditionally guaranteed for one year. Every engine is test-run and tuned before being shipped. Brison 3.2 (shown)-$549. Brison Aircraft, 12075 Denton Dr., Ste. 11, Dallas, TX 75234; (972) 241-- 9152; www.brisonaircraft.com.

Desert Aircraft

Using some of the latest tools and techniques, including 30 CAD and stereo lithography, the DA-150 has been designed from the ground up with Tournament of Champions and World Masters-style competition aerobatics in mind. The DA-150 is ideally suited to aircraft for which existing 120cc and 140cc engines aren't quite enough. It can also power aircraft that are designed for heavier, 4-cylinder, 160cc engines. DA 150 (shown)-$1,495. Desert Aircraft, 140 S. Camino Seco, Ste. # 418, Tucson, AZ 857-10: 15-20) 722-0607: www.desert-aircrafcom.

First Place Engines

Distributed by Sig Mfg., the First Place Engine (FPE) line consists of four, light, powerful gas engines designed specifically for large RC aircraft use. They offer a good power-to-weight ratio and come with a light, tig-welded, custom aluminum muffler that may be modified to accept a smoke system. All four engines come with an electronic ignition, complete instructions and a one-- year warranty; a 50:1 oil/gas ratio is recommended. FIRE (5.8cl, shown left)-$699.95; FIRE (2.4cl, shown right)-$499. Sig Mfg. Co. Inc., P.O. Box 520, Montezuma, IA 50171-0520; (800) 247-5008; www.sigmfg.com.

OIL-TO-GASOLINE RATIOS

The 2-stroke, air-cooled, giant-scale engines we use to power ou models do not have separate oil tanks (unlike full-size aircraft engines), so we must add the oil to the gasoline. Your engine manufacturer provides a mixture ratio recommendation in the engine's operation manual. Here are some common ratios.

HIGH-OCTANE PERFORMANCE FOR GIANT SCALE

FIRING UP

A GAS ENGINE

Before you start a gasoline engine for the first time, it is best to review and become familiar with its operation manual. Even for bench-running, always have a helper. If the engine is already installed in a model, fully assemble the model and have your helper hold it securely. Tell him how to turn the ignition on and off and how to operate the choke, if the engine has one.