Speed 400 revolution

Model Airplane News, Jul 2000 by Aberle, Bob

It's no surprise that Speed 400 motors have become incredibly popular; these versatile power systems can be used with scale and sport models, gliders, pylon racers and even jets! The availability of reliable, lightweight radio components adds to the convenience and appeal of these small electrics, and recent advances in batteries and speed controllers have greatly increased flight duration and performance. These models are generally inexpensive, easy to build and easy to transport, and many of them can fly in smaller areas such as schoolyards. Because this class of aircraft is continually expanding, the accompanying charts highlight only 120 of the available Speed 400-- powered models; check out manufacturer and distributor advertisements and websites for additional aircraft. Also, remember that many small glowpowered planes are great candidates for Speed 400 conversion.

Because the motorsystem component (motor, gearbox, prop, ESC and battery pack) weigh 10 to 13 ounces, the total typical flying weight of a Speed 400-powered model ranges from 15 to 30 ounces. Some of the specialty pylon racers weigh even less than 15 ounces, and even a 16-- ounce model will be a hot performer. For a direct-drive application (more on this later), 20 ounces is a good upper limit, while 30 ounces is about maximum when you use a gear- or belt-drive reduction system.

From a size standpoint, a pylon racer might have only 100 to 150 square inches of wing area, while a powered glider or an old-timer, might have more than 400 square inches. General sport models will tend to have between 200 and 300 square inches of wing area.

Many have categorized the Speed 400-class size as "AA electric" because the power produced by a Speed 400 motor is roughly comparable to that of a .049 glow engine. Speed 400 motors can be found under many brand names and are available in three voltage windings: 4.8, 6 and 7.2 volts (more on this in a moment). Best of all, the basic motor usually costs about $10; the can is sealed, so it can't be repaired. When you wear out a Speed 400, you simply replace it.

Speed 400 motors are used in a variety of applications. The lower-voltage (4.8V) motors are almost always used with lower ratio gear- or belt-reduction drives and smaller props. The mid-range, 6V winding motor on direct drive is good for pylon racers, and with moderate gear- or belt-reduction ratios and 7- to 9-inch-diameter props, it's a good choice for faster models. The highest-voltage winding motors (7.2 volts) are intended for milder sport flying, and these usually have higher gear- or belt-- reduction ratios and are used with larger, usually 9- to 13-inch, props. These motors have more endurance.

Speed 400 motors are easily run "direct" (motor shaft to prop), without a gear- or belt-reduction drive. A 6x3 folding prop, 6V winding motor and 7 cells are good for direct-drive operation. To enhance Speed 400 operation, however, there's a variety of available gear-reduction drives. These allow you to use larger props that turn more slowly and draw less current yet develop more thrust. In other words, the proper reduction drive can lift a heavier model longer. Gear drives (and Speed 400 motors) are offered by such companies as: Hobby Lobby* (Graupner*, Mini-Olympic), Maxx Products*, Dymond ModelSport USA*, Northeast Sailplane*, MTM Intl.* and Modelair-Tech*. Depending on the reduction ratio you use, it is possible to use up to 14-inch props on Speed 400 motors.

For power packs; 7 to 8 cells seem to work well. At S ounces, the Sanyo* 7-- cell 500AR pack is quite popular. Also around that weight is the Sanyo 7-cell 600AE pack, but an even better choice is an 8-cell, 1200 to 1500mAh nickel-- metal-hydride (NiMH) pack, which weighs only about 7.5 ounces. Generally speaking, Speed 400 motors draw an average current of 10 amps. A typical 500mAh pack might give you a 3-minute flight, while a 1500mAh pack might be capable of close to 9 minutes-wow!

Many electric motor speed controllers (FSCs) are now available for use with Speed 400 motors. For this application, an ESC should be capable of handling at least 10 amps of motor current on a continuous basis. Most will operate on at least 6 to 8 cells, and most will have a BEC circuit that allows the motor battery to also power your RC system. Some of the manufacturers or distributors of these ESCs include: AstroFlight*, Hobby Lobby*, FMA Direct*, Castle Creations*, Gordon Tarling*, Modelair-Tech, Sirius Electronics*, Dymond ModeISport USA, Northeast Sailplane, Kontronik* and Viper Model Products*.

If you don't already have a Speed 400-- powered model in your hangar, I hope this article will inspire you to try one of these inexpensive, no-hassle, silent flyers.