Magneto Impulse Coupling lag" Iml lug" ingles By R. G. Muggins, EAA 4755 4915 S. Detroit, Tulsa, Okla. OR EASY INSTALLATION of impulse equipped magF netos, it is believed that an explanation of the impulse coupling "lag" and "lug" angles would be helpful. Most all aircraft magnetos are equipped with an impulse coupling (or impulse starter). An impulse starter is an automatic device which operates only during engine starting. The impulse starter provides an intense spark at cranking speed, at the same time retarding this spark to prevent engine backfiring. When the engine is cranked, the rotor of the magneto is kept from turning by engagement of a catch pin and pawl while a spring winds up in the starter. As the piston passes near top center, the pawl releases the spring, spinning the rotor and generating an intense spark. At a speed of about 200 rpm, impulse starter action ceases and the unit acts as a flexible coupling with the spark automatically advancing to the exact number of degrees before top center, necessary for the proper functioning of the engine at normal operating speed. The accompanying sketches and definitions are offered in the hope that they will be helpful in understanding the terms . . . "lug" and "lag" angles.

ROTATION

LAG ANGLE

The LAG angle is the number of degrees from the advance or running spark position that the impulse coupling lags or retards the spark for starting.

ANTI-CLOCKWISE ROTATION

CLOOCWISB ROTATION

HORIZONTAL AXIS LUG ANGLE The LUG angle is the position of the impulse coupling drive lug with respect to the horizontal center line of the magneto at which the spark occurs for full advance or running position

OP MAGNETO

OF MAOHETO

of the engine.

getters that also make excellent little sportsters and trainers. This is a trend which is to be commended and encouraged. Sport flying would be in trouble without these planes; before a man can fly his new homebuilt he has to learn to fly, and if his homebuilt is a taildragger

why of course he ought to learn to fly in—or at least check out in—a taildragger. Incidentally, the increasingly popular "Reed" method of clipping the wings of J-3 Cubs to make them into capable little aerobatic ships is now being handled by Orville Lippert, who has taken over the plans originally developed by Earle Reed for this conversion job. Lippert, an EAA member, runs an airport at Riverdale, Mien. ®

This neat little Taylprcraft is don; up in blue and yellow and looks much as it did in 1940. Lots of fun to fly and fits right into the vintage section at any man's fly-in.

Clipped wing Cub with white and red polished finish makes a snappy little sportster.

OLD TAILDRAGGERS . . . (Continued from preceding page)

SPORT AVIATION

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