The Incredible Quadractor From Traction, Inc

The Quadractor is a totally new, unbelievably versatile, all-purpose work vehicle from Traction, Inc.

| July/August 1979

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If you need to mow a field, the Quadractor has an attachment for that.


Until very recently, the world's established farm tractor manufacturers refused to accept the reemergence of the small "family farmer." Instead, such firms concentrated upon building more and more massive (and less and less efficient in terms of work performed per dollar) machines. Even the newer—and admittedly much improved—practical-sized farm "workhorses" are destined, by design, to be forever incapable of dragging loads that are significantly greater than their own mass.

On the other hand, the nimble Quadractor—half tractor, half june beetle on casters—[a] turns on a dime, [b] pulls eight times its own weight, [c] climbs a 42° slope, [d] maneuvers over rocks or through streams, and [e] logs, plows, discs, cultivates, and mows. With an 8 horsepower Briggs & Stratton engine, 72-to-1 gear reduction, and an internationally patented powered-suspension system, this strange machine has many of the capabilities of a conventional tractor of 20 to 25 horsepower. However, it requires only a fraction as much fuel as do the larger machines and sells for less than half the price.

Aircraft Technology

All four of the Quadractor's wheels are powered through vertical-shaft gear trains using a technology originally developed by William B. Spence—founder of Traction, Inc. and designer of the Quadractor—for aircraft landing gear. It's this vertical-shaft innovation that lies at the heart of the vehicle's unique performance. In contrast to a massive conventional tractor, the Quadractor weighs only 500 pounds yet can pull nearly two tons! I test-drove one of Spence's little wonders on an inch of new snow—with one end of a 1,500-pound log slung from its belly—and there was no hint of slippage or loss of traction, even when pulling up a 15° incline! It was truly an odd feeling: I was completely aware of the lightness and maneuverability of the vehicle, yet there it was, walking away with an extraordinary load!

A Triumvirate of Engineering Features

The Quadractor is comprehensively engineered for complete traction, and this single-minded approach is responsible for the machine's "muscle." Three related but separate and distinct engineering features contribute to the unusual vehicle's incredible versatility:

[1] First and foremost in importance is the patented design of the four identical vertical drives to the wheels. The Quadractor operates continuously in four-wheel drive, with its left and right sides controlled by separate clutches. Each wheel's power is transmitted from a pulley to the vertical shaft, then down the shaft and through a set of bevel gears to a small pinion gear, which operates the large final-drive cog.

As the pinion gears on all four shafts turn, they tend to walk up the outside of the large final-drive gears. As they climb, the cogs transfer the weight of the vehicle to the tires while simultaneously causing the wheels to revolve. Because the pinion gear housings are offset from their respective wheel hubs (and at the same time are allowed to "travel" within a 15° arc of the drive gears' circumference), the effect of this mechanism is to lift the chassis of the vehicle just at the moment the machine begins to move forward. It's a little like the sensation when the front end of a tractor lifts off the ground, but all four of the Quadractor's "feet" are firmly planted and the weight of the machine—and its burden—is converted into that all-important traction.

[2] Another unique construction feature is the Quadractor's chassis, which is designed to flex over uneven terrain. This "twisting" keeps all four tires securely on the ground and "biting."

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