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  Shelby Cobra Concept

  Jan 7, 2004
  By:  Ford Motor Company
 


Cobra Concept Photo Gallery


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The Ford Shelby Cobra concept, like the legendary 1960s original, features a utilitarian body tightly wrapped around a race-bred engine and chassis. Every surface and line has its roots in the car’s uncompromised performance.

"We let the powertrain, the space frame and the suspension dictate the architecture for the body," said Richard Hutting, chief designer. "The result was a very authentic, modern and desirable shape that does justice to the original Shelby Cobra, but doesn’t share a single dimension or proportion with it."

Through key design details – the dominant grille opening, vertical bumper bars, stacked lamps front and rear, side air extractors and, most importantly, the powerful bulge over each rear wheel – the historical connection to Shelby’s original creation is undeniable.

Surprising Package

While Ford Design is known for its modern interpretations of legendary vehicles – the Ford GT, Mustang and Thunderbird, to name just a few – it also leads the industry in innovative ways to carry people and cargo.

From the Model A to the first Mustang, to the world’s most versatile sport utility vehicles, Ford has a history of packaging efficiency, and the Ford Shelby Cobra concept is no exception.

A key engineering decision – to mount the concept’s six-speed manual transmission at the rear of the car – enabled designers to give the car almost 3 inches more legroom than similar competitors’ performance vehicles, while providing nearly perfect weight distribution.

"From a package perspective, the rear-mounted transmission and the small-diameter, twin-plate clutch made for a larger foot space than typically possible in such a small car with a large engine. This 10-cylinder, 605-horsepower, all-out sportscar has more legroom than in a Ford Crown Victoria sedan," Hutting said. "We also didn’t have to compromise the driving position by offsetting the pedals – an important consideration in a performance car."

Long Wheelbase, Short Overall Length

Performance elements help to define the exterior, as well. Because the engine sits rearward of the front wheels, the front overhang is extraordinarily short. An equally brief rear overhang gives the Cobra concept a 100-inch wheelbase – longer than that of a Dodge Viper, but with a head-to-tail measurement that is more than 20 inches shorter. In fact, the front and rear overhangs are both shorter than on the 1965 Shelby Cobra – the rear considerably so.

These proportions place the Ford Shelby Cobra concept into a league of its own among production-feasible vehicles, communicating rear-drive power and serious performance. The car's stance on the road is unmistakably purposeful, with only 4.5 inches of clearance between the carbon-fiber chin spoiler and the pavement. From the rear, powerfully bulging wheel arches embrace the massive 19-inch rear wheels, signifying that that’s where the power comes to the ground.

Clean, Unadorned Surface Language

Just as designers used the mechanical package to drive the Ford Shelby Cobra concept’s proportions and attitude, they drew from the car’s racing persona to create a clean, unembellished "wrapper" for the powertrain and chassis.

The front section of the body is a forward-tilting "clamshell." This simple design provides immediate, wide-open access to the powertrain and front suspension while defining the clean hood profile. Prominent design elements include the oversized grille opening for the radiator and the chin scoop below it for the oil cooler.

The headlamps and driving lamps at the front of the car are stacked vertically, as on the original Shelby Cobra.

"These lamps, combined with the vertical billet-aluminum bumper bars, the grille opening and the muscular fenders, are the way the front of the concept communicates ‘Cobra,’ " Hutting said.

In character with the Ford Shelby Cobra concept’s uncompromised performance, there are no windshield wipers, no side windows and no convertible top – it is a fair-weather-only racing machine.

The sides of the body are pure function. Just aft of each front wheel is a prominent rectangular air extractor – to cool the engine and the brakes – and a conventional forward-swinging door with a dramatically simple shut line that terminates at the rear fender. To emphasize the clean body sides, designers also omitted door handles.

The decision to forgo exterior door handles left the team with a quandary: How do you open the doors? They briefly looked at incorporating an electronic button but settled on the original, elegantly simple Cobra solution of placing the inside handle up high, where it can easily be reached from outside the car.

"It’s a race car," Hutting said. "The driver would rather reach inside to open the door than carry the weight of two more handles."

Aluminum A-pillars and dual roll hoops behind the low-back seats are modern touches that expose the advanced aluminum space frame while echoing the form and function of the classic chrome roll hoops used on some original Cobras.

Rearview Camera System for Clean Flanks

In keeping with its racing mission, the Ford Shelby Cobra concept does without side mirrors in favor of a higher-tech, lower-drag design. A trio of video cameras – mounted high in each A-pillar and at the center of the windshield frame – create real-time color images that are displayed on a digital version of the traditional center-mounted rear-view mirror. The images from each camera are stitched together on this liquid-crystal display to form a perfect 180-degree panorama of the competition.

A mere 27 inches of rear overhang (measured from the axle line to the bumper) and other rear design details further develop the themes of uncompromised performance and Cobra heritage.

Benefiting from four decades of aerodynamics research, the Ford Shelby Cobra concept departs from the original car by incorporating carbon-fiber "barge boards" to manage air extraction from the side vents, and a carbon-fiber diffuser in the rear to create downforce. These aerodynamic aids borrow heavily from wind tunnel lessons learned with the Ford GT and Formula 1 racing and were devised and tested with the aid of computational fluid dynamics software.

The rear transaxle cover is left exposed and becomes a design element that conveys mechanical strength.

Small, stacked round taillamps and vertical billet-aluminum bumper bars subtly trace their bloodlines back to the original Cobra.

"Even within the very modern framework of the short overhang and exposed underbody aero effects," Hutting said, "the rear of the car has Cobra cues to connect it to the legend."

A bright, Tungsten Silver metallic paint reinforces the car’s mechanical precision, while twin stripes in a lighter shade of silver run fore and aft over the hood and rear deck, in a nod to Shelby’s traditional race car stripes.

Seven-spoke BBS racing wheels were chosen for strength and light weight. Dramatically larger than the 15-inch wheels of the original Cobra, they measure 18 inches in front and 19 inches at the rear. The wheels wear lower profile rubber all around – with the massive 35-series rear tires measuring more than 13.5 inches wide.

"When you see those massive tires under their bulging fenders and those exposed aerodynamic aids, you know at a glance that this is a serious racing machine," Hutting said.

Purposeful Interior

Proving that a minimalist roadster also can be comfortable, the 605-horsepower Ford Shelby Cobra concept offers none of the traditional electric amenities, yet boasts more front-seat legroom than a Ford Crown Victoria sedan.

The rear-mounted transmission offers a huge advantage in interior packaging: The driver and passenger are positioned close together near the vehicle centerline and separated by a narrow driveline tunnel. The spacious foot wells are nearly rectangular, in marked contrast to vehicles where the transmission tunnel hump severely restricts the driver’s foot room on the right, or the front wheel intrudes on the left – or both. The Ford Shelby Cobra concept driving position is comfortable and ergonomic, with an adjustable steering column.

The carbon-fiber racing seats with five-point belts offer support for high-performance driving. Their low-back profile – a nod to traditional sports cars – is made possible because the roll hoops behind the seatbacks are padded to double as head restraints. This allowed designers to capture the old-school feeling of the original Cobra seats in a thoroughly modern execution.

The cockpit is trimmed in aluminum, with electric blue splashed on the seat trim and steering column. A full-width aluminum instrument panel spans the cockpit in one unbroken swath – a throwback to the true "dash boards" of yesteryear and a contrast with today’s driver-centric cockpits. Instruments include a 220-mph speedometer, 10,000-rpm tachometer and critical temperature and pressure readouts.

There is also a fuel pump switch, an under-hood fire-suppression system release and an emergency master kill switch to comply with racing rules.

What’s missing? "There’s no audio system at all," Hutting said. "The tuned exhaust makes its own music."


At the time Carroll Shelby began his Cobra project in 1962, England’s AC Cars had a beautiful little open-top car that needed an engine. Ford had the industry’s best family of V-8 engines. Shelby saw the possibilities and brought the two together. The rest is history.

"The Ford engines turned out to be a great choice," Shelby said. He first tried the 260- and 289-cubic-inch Ford small block V-8 engines before settling on the massive 427 as the ultimate Cobra engine.

For the next chapter in the Cobra legend, the modern Ford team also had a few powertrain options. They included the supercharged
5.4-liter V-8 from the Ford GT, as well as turbocharged 4.6-liter and 5.4-liter mills. Outstanding engines, yes, but they didn’t pack the spiritual punch of Shelby’s overpowering Ford 427.

They needed something more, something that would capture the essence of that 427 in a modern roadster. They found it in a satellite Ford engineering operation devoted to developing new powertrain technologies away from the narrower demands of product development.

In an atmosphere that is part think-tank and part speed-shop, the Advanced Powertrain team develops technologies that frequently have as many applications on the race track as in consumer vehicles.

For approximately two years, they had been working on an all-aluminum V-10 targeted at ultimate, naturally aspirated performance. When they bolted this beast into a Mustang chassis for evaluation, it only took one drive to confirm its potential.

"The Ford Shelby Cobra concept just begged for this engine," said Graham Hoare, director, Ford Research and Advanced Engineering. "Although it’s not yet ready for production, we’ve reached a credible engineering level for such a serious concept car – and it has a modern soul that matches the famous 427."

Blending the Advanced Powertrain team’s work with elements from the 4.6-liter, 4-valve V-8 used in the 2004 Mustang Mach 1, the resultant Ford Shelby Cobra concept engine has 10 cylinders and is bored and stroked for a 6.4-liter displacement, or about 390 cubic inches. It produces 605 horsepower at 6,750 rpm and 501 foot-pounds of torque at 5,500 rpm without supercharging or turbocharging.

"In many ways, it’s not very exotic," said Hoare. "It uses the same basic castings and assembly techniques as our production modular engine family. The output, though, is phenomenal. If you can’t get in trouble with this kind of power, you’re not trying hard enough."

Kevin Byrd, the V-10 project leader, thinks of the Cobra V-10 as an all-star combination of current Ford engine technologies. "This engine is an amalgam of everything right about Ford engines. We took the best that the modular engine family has to offer, then added some tricks of our own. The V-10 is a culmination of 100 years of building engines," he said.

The double-overhead-cam cylinder heads and cylinders are fed by port fuel injection and racing-derived velocity stacks that are just visible within the hood scoop. For a low hood line, the throttles are a slide-plate design and the lubrication system is the dry-sump type, which relocates oil from underneath the engine to a remote tank. The engine proudly wears brushed aluminum "Powered By Ford" valve covers.

The rear-mounted six-speed transaxle is identical to the high-performance unit in the Ford GT, with an integral limited-slip differential to drive the rear wheels. Based on the engine’s 7,500-rpm redline and the drive ratios, this Ford Shelby Cobra concept has a theoretical top speed of more than 260 mph and would break 130 mph in third gear, although it’s electronically limited to 100 mph – for now.

Front-Mounted Engine and Torque Tube

One of the challenges of fitting a 10-cylinder engine into a compact roadster is leaving room for the driver’s legs and feet. With a conventional transmission mated to the back of the engine, the tradeoff between hood length and passenger room often makes for a cramped footwell and dramatically offset pedals – a flaw of the original Cobras and many modern sports cars.

Because the Ford Shelby Cobra concept was planned from the outset to be a production-feasible "runner," not just a pretty show car, the team had to address the legroom concern. They found that mounting the transmission at the rear of the car, connected to the front-mounted engine with a torque tube, let them use a very narrow "tunnel" between the seats.

Compared to a conventional driveshaft, which is typically mounted behind the transmission, a torque tube-style driveshaft spins considerably faster because it is running at engine speed. The spinning inner shaft is supported within a stationary outer tube that stabilizes the engine and transmission in bending and in torsion. The inner shaft taps crankshaft torque via a twin-disc, small-diameter clutch mounted at the rear of the engine.

Computer-aided design was essential in helping the first prototype come together smoothly. "Because they spin so much faster than driveshafts, these torque tubes can be a nightmare in terms of vibration," said Manfred Rumpel, manager, Advanced Product Creation. "Using our electronic tools, we optimized the location of the driveshaft support bearings, and it ran smoothly on the very first try. This type of modern engineering tool gives us a development advantage that pioneers like Carroll Shelby could only dream about."

Creating a New Chassis From Existing Parts

Although the AC Cars 260 roadster was the starting point for the original Cobra, the Ford Shelby Cobra concept team had no obvious existing architecture suitable for the project.

"We knew we wanted a front-engine car that had to be ultra-compact and lightweight, yet robust enough to handle 605 horsepower," said Theodore. "There was nothing that fit the bill on first glance."

But Rumpel’s team saw a creative solution.

"We were already planning to use the Ford GT suspension systems, and we asked ourselves how much more of the GT we could borrow," he said.

Quite a lot, as it turns out. Even though the GT is a mid-rear-engine car, and the proposed roadster was to have a front engine, a decision to mount the transmission at the rear made the connection.

"Once we really started looking into it, we had an epiphany," Theodore said. "The project took on a new sense of purpose when we really started leveraging the Ford GT engineering."

The team worked long hours with John Coletti, head of Ford’s Special Vehicle Team, to maximize the commonality. Fresh from completing the all-new Ford GT in just 15 months, Coletti understood what it took to build fast cars faster than ever. "It was a great team effort," Coletti said.

The bulk of the rear structure is made from slightly modified Ford GT components, including the massive, trellis-like cast aluminum suspension nodes, the rear rails and bumper beam, a major cross-member and the brackets used to mount the transmission.

The center portion of the space frame also has a high degree of GT commonality–major aluminum extrusions are based heavily on existing pieces. At the front of the roadster, the team incorporated the extruded main rails, steering rack cross-member, crash-management sections and the bumper beam.

"The concept car was even assembled using the prototype jigs the GT team no longer needed," said Rumpel. "This commonality and re-use goes hand-in-hand with our speed and cost efficiency."

Overall, the Ford Shelby Cobra concept is more than 2 feet shorter than the GT, with a wheelbase nearly 7 inches shorter. Even the track width has been reduced by more than an inch. That the concept car and the GT share any parts at all is a testimony to the flexibility of the space frame design and the creativity of the chassis team.

Ford GT Suspension, Steering and Brakes

To attach the massive 18- and 19-inch wheels and tires to the car, the team chose to use the Ford GT suspension system with a few modifications to accommodate the increased weight up front. Like engine technology and electronics, suspension design has come a long way in more than 40 years.

"The original leaf-sprung Cobras were awesome on the straightaway but didn’t make a name for themselves in the turns," said Rumpel.

Theodore was even more direct, "The original 427 was a beast."

The new Ford GT earns praise for its combination of agility, grip and easy-to-drive character, a reflection of its sophisticated suspension design and the expertise of its chassis engineers. The Ford Shelby Cobra concept applies the best of the GT suspension to a big-engine roadster.

A double-wishbone suspension design with unequal-length aluminum control arms, coil-over monotube shocks and stabilizer bars is used front and rear. The upper control arms are identical at all four wheels and are made with an advanced rheo-cast process that allows the complexity of form associated with casting, yet retaining the strength of forging. The metal, heated to just below its melting point, is the consistency of butter when it is injected into a mold at high pressure. Pressure is maintained as the part cures, preventing porosity in the final product for exceptional strength.

The steering rack also is borrowed from the Ford GT, with a few modifications. The steering column, like the Ford GT’s, draws on Ford engineering best-practices like the low friction, high stiffness and light weight that have made the Ford Focus steering column among the best in the industry. Braces between the front shock towers and below the isolated engine mounts improve torsional rigidity and aid steering response.

With more than 600 horsepower available at the throttle pedal, the brake pedal had to be equally potent. The team set braking distance targets comparable with today’s best sports cars, and turned to the Ford GT braking system for suitable components.

Brembo "monoblock" one-piece aluminum brake calipers with four pistons each grab cross-drilled, vented discs at all four wheels. The discs are a massive 14 inches in front and 13.2 inches in the rear, for fade-free stopping power. But the team stopped short of fitting the car with an antilock braking system, in keeping with its racing character. Brake balance is biased slightly to the front wheels to aid stability.

For packaging reasons, the team devised a novel offset actuation linkage for the brake booster and master cylinder, so the brake pedal can be placed in a normal position even though its hardware is off to the side of the engine bay.

The one-piece BBS wheels are wrapped by BF Goodrich Z-rated racing slicks, size 275/40R18 in front and 345/35R19 in the rear.

Ford Shelby Cobra Concept Specifications

Vehicle Type

Open-top V-10 roadster

Powertrain and Chassis

Chassis construction

Welded and bonded space frame of cast and extruded aluminum

Dimensions (in inches unless otherwise noted)

Wheelbase

100.0

Overall length

155.4

Overall width

75.0

Track width, front

60.6

Track width, rear

60.4

Front legroom

45.4

Curb weight

3,075 pounds (target with production-level bodywork)

Engine

Type

6.4L, 90-degree V-10

Configuration

Aluminum engine block and cylinder heads

Redline

7,500 rpm

Valvetrain

DOHC, 4 valves per cylinder

Intake

Velocity stacks with sliding plate throttles

Bore x Stroke

3.66 x 3.70 in / 93.0 x 94.0 mm

Displacement

390 cu in / 6,392 cc

Compression Ratio

10.8:1

Horsepower

605 @ 6,750 rpm

Torque

501 lb-ft @ 5,500 rpm

Drivetrain

Layout

Mid-front engine, rear transmission, rear-wheel-drive

Transmission

Type

Ricardo 6-speed transaxle

Gear

Ratios

Theoretical top speed at redline

1st

2.60:1

64 mph

2nd

1.70:1

98 mph

3rd

1.23:1

135 mph

4th

0.95:1

175 mph

5th

0.76:1

219 mph

6th

0.63:1

267 mph

Reverse

3.14:1


Final Drive

3.36:1 limited slip


Suspension

Front

Unequal-length aluminum control arms, coil-over monotube shocks, stabilizer bar

Rear

Unequal-length aluminum control arms, coil-over monotube shocks, stabilizer bar

Steering


Type

Rack-and-pinion with power assist

Ratio

17.0:1

Brakes


Front

14.0 x 1.3 in. (355 x 32 mm) Brembo cross-drilled and vented discs, four-piston monoblock calipers

Rear

13.2 x 1.3 in. (335 x 32 mm) Brembo cross-drilled and vented discs, four-piston monoblock calipers

Tires and Wheels

Front

P275/40R18 BF Goodrich racing tires on 18 x 10-inch BBS wheels

Rear

P345/35R19 BF Goodrich racing tires on 19 x 13-inch BBS wheels




Cobra Concept Photo Gallery



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