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GM Motorama Firebirds


The GM Motorama Firebird III

A series of exotic subsystems totally filled the innards of the GM Motorama Firebird III. The most interesting was Unicontrol, a joystick that allowed the driver to go, stop, and steer with a single lever. Push it forward to accelerate, pull it back to brake, move it side to side to turn.

For reverse, you rotated the lever 20 degrees left or right; Park was selected by an 80-degree twist. All these actions were accomplished by servos controlled by three primitive analog computers, which not only gave the joystick some "feel" but also centered the steering.

The GM Motorama Firebird III
The snazzy -- and influential --
GM Motorama Firebird III.


The computers monitored vehicle speed and front-tire turn angle to ensure that the driver didn't "outsteer" the car. In other words, if the driver suddenly shoved the stick too hard to one side, cranking in too much steering lock, the computer scaled back and balanced steering, braking, and acceleration inputs so the car wouldn't careen out of control or turn over.

There was also a large onboard electronics package that took up most of the space between the Firebird III's U-shaped engine cradle and the left rear body. The fuel tank and twin 12-volt batteries balanced this on the right side.

The GM Motorama Firebird Ill's 12-bhp APU (for Auxiliary Power Unit, a small piston engine) drove the 1,000-psi steering and braking pumps, activated the airbraking flaps as on the Firebird II, powered both a 110-volt alternating-current generator (so that the car didn't need to be plugged into house current for outdoor demonstrations) and another generator for the 12-volt batteries, drove the air-conditioning compressor, and supplied up to 3,000 psi for the air/oil suspension system.

The interconnected suspension canisters automatically adjusted ride height, which depended on car speed and gave a variable-rate spring effect by its valving.

Firebird Ill's front suspension was unusual for the late 1950s in that it used a good old-fashioned beam axle. But unlike 1930s installations, this axle was located by four control arms anchored to the front subframe. Not only did this arrangement make for a lower front silhouette but, in combination with the deDion rear, it offered a roll center only 19 inches off the ground.

The GM Motorama Firebird III's brakes were also unusual. By the late 1950s, GM Research realized that the days of drum brakes were coming to an end, and discs would soon take over. Yet for the Firebird III, GM designed and built the ultimate set of automotive drum brakes: 11x4-inch drums cast into each of the car's alloy wheels. The drums were faced with iron, and the shoes used sintered metallic linings. Special cast-in cooling passages between the drum and wheel surfaces took in air at the hub and spun it out through slots in the perimeter.

The GM Motorama Firebird III preparing to perform on GM's Mesa, Arizona, proving grounds.
The Firebird III prepares to perform at GM's Mesa,
Arizona, proving grounds. An improved GT-305 gas
turbine engine was housed in the rear of the car.
A small four-cylinder piston engine in front
powered various subsystems.


Also unusual was the Firebird Ill's use of antilock brakes and a so-called "grade retarder." The latter comprised a series of friction discs acting on the rear axle shafts. The discs ran in oil and were brought to bear during deceleration with fluid pressure from the automatic transmission. Both the grade retarder and the airbrake flaps kicked in during stops from over 30 mph.

After getting the Firebird III up and running. General Motors commissioned a movie that documented the car's styling and engineering development, and highlighted its many features. Much of the footage was shot at GM's Mesa Proving Grounds, where the car performed beautifully. Parts of the movie were shown at the 1959 Motoramas.

What did the future hold for GM and its series of Firebirds? Continue to the next page to find out.

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