Type: technology demonstration concept car
Powerplant: 1 x three-cylinder 1.5 l engine
Significant date: exhibited in 1992
The General Motors Ultralite was a 1992 low emission vehicle concept car intended to demonstrate the benefits of advanced materials and low fuel consumption. The Advanced Engineering Staff of General Motors designed a technology demonstration vehicle with interior room capable of seating four full size adults, and with excellent visibility, handling, performance, emissions and fuel consumption. The shape was remeniscent of the Ford Probe concept, and the Ultralite presaged the production General Motors EV1 electric vehicle and other production models.
For this revolutionary monocoque vehicle, the wizard of Scaled Composites, Burt Rutan (coincidentally, later an EV1 driver), designed the composite carbon fiber shell, which amounted to only 425 pounds. The resulting aerodynamics—a 0.19 drag coefficient—weren't surprising. Its stiffness and attention to lightweight detail, however, did surprise, right down to the light rubber bands in its seats. The total weight was 1,400 pounds, with just 4 hp needed to propel it at 55 mph. General Motors built the Ultralite in six months. The goal was to make a four passenger show car capable of 100 mpg. The demonstrated concept car achieved a composite city/highway fuel rating of 62 mpg, and 100 mpg in open highway driving at 50 mph. It was rated at 88 mpg (highway) by the EPA.
The Ultralite used a two-stroke engine in a “power pod” at the rear of the vehicle. The engine had been developed from an East German design. The three-cylinder 1.5 l engine could produce 111 hp (which made a speed of 135 mph possible) and weighed 40% less than a conventional engine while producing as much power. It was expected to run cleanly enough to qualify as an ultra-low emissions vehicle under California’s tough new rules. The concept also incorporated low rolling resistance tires.
The structure had to support two large gull wing doors, which comprised about one third of the car's outside area, and still meet the vehicle's strength and stiffness requirements, as well as forward, side and rollover impact criteria for GM automobiles. Despite only two doors, the Ultralite was designed much like a sedan. The lightweight doors open easily for excellent access to the rear seating area. Also included was an integral fuel tank, suspension mounting hard points, rear seats and other structural details. The Ultralite did not have the benefit of a "B" pillar to aid in the overall structural stiffness; it was deleted to allow easy access to both the front and rear seats. In addition, every effort was made to minimize the number of individual structural components in the chassis and body structure.
The Ultralite program had a very aggressive schedule, so Scaled elected to use its proven low temperature - low cost rapid prototyping tooling methods. Female tools were fabricated over a GM supplied master model, and GM supplied lofts were used to make templates for the master plug for the chassis section. An assembly fixture was fabricated to ensure accurate assembly of the structural components.
A carbon fiber skin/PVC core sandwich panel structure was chosen for all the primary and secondary structure for the 10 chassis/body components. The sandwich structure used carbon fiber cloth, for skins with PVC foam for the core. IM-7 stranded roving was used to provide continuous load paths from the roof around through the door mounts and down on to the chassis. The IM-7 roving was also used to provide similar continuous load paths from the front suspension mounts through the chassis tunnel terminating at the aft structure bulkhead. The rear suspension/ transmission/ engine package attached to this bulkhead. This system enabled the GM engineers to easily change powerplants without modifying the composite structure.
Two complete all-graphite vehicle structures were designed, fabricated, and ready for delivery within 12 weeks after program start. The vehicle structural weight including two doors, front and rear bumpers and interior components was 420 lb, which was within 1% of the original structural weight estimate. Engineering structural stiffness tests conducted by GM showed the structure to be considerably stiffer than anything previously tested.
Since its debut in 1992, the Ultralite has won several major awards including the gold Medal IDEA Award for Design Explorations from the Industrial Design Society of America, the Grand Award in Automotive Technology from Popular Science magazine, and the Most Outstanding Concept Car of 1992 award from Japan’s Car Styling magazine. The Ultralite program conclusively demonstrated Scaled's unique structural design capabilities, stringent weight control, and rapid response characteristics, as well as its ability to work well as a team under a very tight schedule, with the largest corporation in the world. Although material costs and manufacturing methods for the project were not realistic, it did prove the value of parts consolidation, weight reduction, corrosion resistance and styling latitude.
Population: 2 frames built by Scaled Composites