Fisker's First Hybrid Features Aluminum Frame

Fisker's First Hybrid Features Aluminum Frame A super-structural tunnel is the vehicle's backbone Doug Smock, contributing editor -- Design News, March 1, 2010 Aluminum will play an important role in lightening new electric and hybrid cars.

Exhibit A is an advanced aluminum space frame in the Fisker Karma sports car that debuts tomorrow at the Geneva Motor Show in Switzerland.

Fisker Automotive's engineering team designed the Karma's space frame around the car's Q-DRIVE® series-hybrid powertrain, filing for multiple patents. Q-DRIVE® features a 2.0L turbocharged ECOTEC® engine/generator set, a lithium-ion battery pack from A123 Systems and a rear-mounted 403 hp traction motor assembly.

The Karma, whose prototype was first shown in January 2008 at the North American International Auto Show, is expected to have a sticker price of $87,900. The vehicles will have a range of about 50 mi as an electric vehicle, and will only require one gas fill-up a year if operated strictly on the electric motor.

The space frame minimizes weight through use of 5000- and 6000-series aluminum alloys and a unique extrusion-intensive architecture. 5000 series are alloys made with magnesium, and derive most of their strength from work hardening. 6000 series are alloyed with magnesium and silicon, and are easy to machine.

"Our top priorities when we designed the Karma's aluminum space frame were that it have extremely high torsional rigidity and could be easily modified to accept Karma model variants," says Henrik Fisker, CEO, Fisker Automotive. "We benchmarked some of the world's best cars to create an all-new space frame that will deliver an exhilarating experience behind the wheel."

Torque Tube

A super-structural tunnel running down the car's centerline is the backbone of the vehicle. It not only houses the battery pack but acts as a torque tube connecting front and rear sections. For optimal strength the Karma's space frame is joined with 79 m of precision welds and 1,058 self-piercing rivets.

Few cars match its statistics:

Static torsional rigidity – the amount the space frame resists twisting forces when entering a ramp at an angle, for example – measures more than 33,000 Newton-meters per degree (Nm/deg).

Static bending rigidity – the amount the space frame resists flexing forces as the car enters a ramp straight on, for example – measures more than 23,000 N/mm.

Dynamic stiffness – the space frame's resistance to resonant vibrations like those felt when driving over a sharp bump or rough road surfaces – is also world class.

Front-impact protection starts with a patent-pending, multi-cell tempered aluminum crush box that displaces high-impact energy away from passengers. Its design permits easy replacement, reducing repair costs that could lower insurance premiums. Dual Phase 600-Series steel-reinforced components in the doors and "B" pillars provide side-impact protection.

And the lithium-ion battery's location in the center of the car places it away from impact areas. The Karma can be fitted with a solar-paneled roof to aid in the recharging of its batteries and  also to help power the cabin climate control system. The factory-fitted solar roof can generate up to a half kilowatt-hour a day, boosting range up to 4 to 5 mi when the sun is shining.

Valmet Automotive will assemble the space frames at a plant in Uusikaupunki, Finland that has been used to produce Porsches and Saabs. Fisker Automotive operates an R&D center in Pontiac, MI. "The Karma is scheduled to start arriving in showrooms late this year," says Russell Datz, director of public relations for Fisker. " We have a network of 45 U.S. retailers that have existing showrooms and service centers."

Based in Irvine, CA, Fisker was created in 2007 to leverage the design capabilities of Fisker Coachbuild, LLC, founded by auto design veterans Henrik Fisker and Bernhard Koehler, and the PHEV powertrain capabilities of Quantum Fuel Systems Technologies Worldwide, a Tier 1 supplier of clean vehicle technologies. Previously, Henrik Fisker was design director for Aston Martin and president and CEO of BMW's DesignworksUSA. Koehler, whose title is chief operating officer, led operations for Ford's Global Advanced Design Studio and created concept cars for Aston Martin, MINI and BMW.

The first product of the collaboration is the four-door Karma, described as the world's first premium plug-in hybrid electric vehicle (PHEV). The Karma will be followed by a second line of lower cost, high volume automobiles by 2012.

According to data from the Aluminum Association of America: