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From the GM media site:

One of the most distinguishing features of the all-new Chevrolet SSR is an ingenious power-retractable hardtop system that assures an open-air driving experience without impeding the vehicle's truck-like utility.

Also called a "top stack", the retractable hardtop on the SSR is the first ever applied on a pickup-styled vehicle. It is the only system of its kind where the roof panels move independently to "stack" vertically behind the passenger compartment - a design that ensures quick operation and minimal stowage requirements.

A single button on the console transforms the SSR from an enclosed roadster to a convertible in less than 30 seconds, neatly tucking the roof panels rearward in waterfall fashion between the passenger compartment and pickup bed. The unique vertical storage system is an important enabler for the vehicle's ability to emulate the utility of a pickup - even with the top down, the SSR's bed capacity remains unchanged.

"As far as we know, this is the only retractable hardtop system with roof panels that actually operate independently, held together by a linkage, as they move," explained Gary Forgue, chief engineer for the retractable roof system.

"Other known production systems use panels hinged together that 'clamshell' as they retract or deploy - but due to space requirements, we needed to develop a system that stowed vertically. We didn't want to compromise the vehicle's cargo bed utility."

According to Forgue, most of the major components of the top system are packaged as an assembly - this brings a number of benefits including reduced vehicle build complexity, enhanced cross-vehicle structural rigidity, and easy service of the system.

"The system is assembled off-line during the manufacturing process and is dropped into a structural bulkhead that's been designed into the SSR's upper body structure between the box and the passenger compartment," Forgue explained. "Once it's attached with eight bolts, it literally becomes a structural element of the vehicle and brings enhanced cross vehicle rigidity."

The design process for the SSR's retractable roof system was completed in about four months - a remarkably quick turnaround considering the level of innovation incorporated. A team of engineers from General Motors, ASC Incorporated, and Karmann USA developed the system, which has been designed for long-lasting, reliable performance.

Via depression of a single button, the SSR is transformed into a convertible in a smooth, quiet kinematic sequence orchestrated by the system's controller using information collected from a series of sensors.

The button that actuates the sequence must remain depressed until the entire event is complete...releasing it at any time temporarily halts the process.

The following outlines the sequence of events:

Initially, the controller automatically lowers the driver and passenger side windows to ensure they are clear from seals in the roof panels. As soon as the windows are clear of the seals, the rest of the process begins;

Latches release the system's tonneau, a body-color panel stretching the full-width of the vehicle between the passenger compartment and the pickup bed. The tonneau swings up to a vertical position, then latches release the forward roof panel from the header (top edge of the windshield);

As the top panels begin to cycle down, a body-color section called the "flipper door" moves upward from its vertical position in the storage area to allow the top to pass by;

As they cascade downward and rearward, the two top sections separate and nest rear-under-front as they retract vertically into the storage area;

The flipper door and tonneau then close over the panels. Together with the fixed body-color "waterfall" panel, which ties the tonneau to the interior between the seats, they close the top storage area completely for a smooth, flush appearance and leak-free performance; and,

A series of latches in the storage area holds the mechanism securely down and locked in place for rattle-free stowage. The latches can be over-ridden so the top can be manually lifted, deployed and secured in the unlikely case of a power failure.
Just as with the top-down process, pushing and holding the button converts the SSR back to a closed-cabin roadster. If the windows are up, the controller lowers them to allow the top to find its true position without interference from the door glass.

The controller also has the capability to "index" the door glass position. For example, when a door handle is pulled, it drops the glass in that door just slightly to clear the seals. When the door is closed, the glass comes back up against its seals.

Quality & Durability
In both development and assembly, the retractable top system on the SSR goes through rigorous testing to ensure optimal, dependable performance.

The tests are conducted "off-line" which enables focused functional evaluation and durability testing. The system is validated to achieve the durability of three vehicle "lifetimes" - or approximately 8,000 operation cycles. Extensive water testing is conducted on the system both as an assembly and as assembled on the vehicle.

Off-line assembly and low volumes enables every opportunity for quality assurance. System durability is ensured through the following:

Roof panels made of heavier gauge steel stampings;
The linkage bars are primarily ¼" (6.3 mm) steel for strength and rigidity - a heavier gauge than what's found on most retractable roof systems;
A well-isolated electro-hydraulic power system, combined with strategically located bushings, eliminates metal-to-metal contact for long life and smooth, quiet operation. The bushings protect the integrity of the linkage joints so the fits do not change over time. This virtually eliminates the chance of looseness or rattling; and,

Optimized design and assembly minimizes wind noise in the cabin with the top up, and an optional wind stop will be offered to fit between the seats and buffer turbulence with the top down at highway speeds.
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