GM Ultralite Show Car
The Advanced Engineering Staff of General
Motors designed a technology demonstration vehicle called
the Ultralite, an automobile with interior room capable
of seating four full size adults, and with excellent visibility,
handling, performance, emissions and fuel consumption. Scaled
Composites was selected to design the composite structure
for this revolutionary vehicle.
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. 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.
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.
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