Resources: Hawk Vehicles
Shadow Hawk raises the bar for high-performance cars.What do you get when you cross a Corvette with the original military Hummer? A heck of a hybrid. But it still wouldn’t have the outrageous performance and capabilities of the Super Terrain Vehicles (STV) being designed and built by Shadow Hawk, Broomfield, Colo. The company has plans for six versions of its STV: the Desert Hawk, an off-roader; two for the military, the Armor Hawk and Battle Hawk; an RV version, the Terra Hawk; a high-speed coupe, the Street Hawk; and a slightly less-expensive, less-capable “entry-level” version, the Steel Hawk. The vehicles will hit the market late this year, with the company planning on building a dozen over the first 12 months. After that, they intend to manufacture 15 to 18 per year, with the least expensive, the Steel Hawk, going for $750,000, and the rest starting at $1 million. It should take about 18 months to build each one, and buyers will be able to customize nearly every aspect of the car.
Engine and chassis At the heart of all the Hawks, except the Steel Hawk, is a 6.6-liter diesel V8, a pumped-up derivative of a mass-produced engine. A diesel was chosen based on its ability to crank out lots of power at usable rpms. The engine uses compound turbocharging, high-pressure direct fuel injection, and state-of-the-art computer controls to generate 1,100 hp, 1,805 lb-ft of torque, and 0 to 60 times of 3.5 sec. Top speed is about 208 mph, which takes about 11 sec to reach. Still, the vehicles get 20 mpg and meet current and expected emission standards.
To make the engine rugged and reliable, it sports a double-vacuum-melted alloy-steel crankshaft and rods and special alloy pistons. A partial vapor-deposition coating on the camshaft, valve train, and pistons cuts friction so the components last longer.
A Spider Drive splits engine power, sending torque to each wheel. It consists of a mechanical transaxle and a series of geared shafts that transmit power through electronically controlled hydraulic clutches. The transmission is not friction based, which means it can take the abuse and forces generated when off-roading or towing. It can also provide traction and stability control said to be far better than the brake-based versions found on other cars and trucks. The Spider Drive can handle up to 2,500 lb-ft of torque, more than an STV’s engine can generate and unprecedented in a transmission this size, according to the company. But Shadow Hawk engineers wanted to ensure transmissions wouldn’t fail, wouldn’t even hiccup, when the vehicle is “a thousand miles from civilization.”
The engine nestles into a monocoque structure that combines the chassis and skin of the vehicle in a single component. Much of the engine actually stretches back into the passenger compartment, putting the center of gravity near the center of the vehicle, ideal for handling. A 50-gallon fuel tank, which gives most STVs a 1,100-mile range, also mounts close to the center of gravity. (The Steel Hawk is slightly heavier and carries a different engine, so its mileage figures will be slightly less.)
The 1,600-lb monocoque made of 3/16-in.-thick titanium is rigid, strong, relatively light, and rustproof. The strength is needed to support the highly adjustable and articulating suspension in which each wheel is supported by an air spring. Hydraulics at the top and bottom of the springs let the driver alter the vehicle’s pitch and roll attitudes.
The driver can independently extend each wheel 44 in. or retract it by up to 2 in. Retraction, which must be done when the vehicle is stopped, is used for a couple of reasons. By raising one wheel and letting the vehicle balance on the remaining three, the driver can change the raised tire without using jacks. And with all wheels retracted, one STV can be stacked on top of another for efficient storage or transportation.
Wheel extension also depends on vehicle speed, with full extension available at speeds up to 10 mph, but extension is limited to between 2 and 14 in. when traveling faster. The independent control lets the driver handle some tough situations. For example, to avoid a fallen log or boulder blocking the path, the driver can fully extend three wheels. The STV will balance and drive on those three wheels, while the fourth goes over the obstacle. Once cleared, the driver can extend the fourth wheel and lift another so it can avoid the obstacle. In fact, with practice, a driver could make a Shadow Hawk STV climb a set of stairs while constantly maintaining at least three points of contact.
The active suspension includes camber control to keep each tire’s contact patch flat and on the ground whether the Hawk is going straight or through a turn whether the wheels are extended or not. This lets the inside tires work nearly as hard as the outside wheels during hard cornering. Caster, which the driver can set, is also automatically maintained regardless of wheel extension. So the driver can fine-tune the amount of feedback he gets from the road.
An Energy Impact Control subsystem on the suspension absorbs impacts without damaging the vehicle or affecting driver control. It consists of horizontal and vertical shock absorbers at every wheel. When a wheel hits a bump or rock, the shock absorbers dissipate much of the force while letting the wheel move rearward, raise up and over the obstacle, then return to its previous driving position.
All four tires on the STV are the same: 40-in-tall, 15.5-in. wide, and mounted in 22-in. wheels. According to design calculations, a Street Hawk will withstand 1 g on a skid pad.
The STVs do not rely on friction brakes for stopping. Instead, wheels are forced to run gear pumps, with a control valve on each pump dictating how much brake pressure is applied. This, plus some computer controls, contributes to the vehicle’s ABS and traction control. An accumulator stores hydraulic pressure built up during braking, which can be released on demand to turn the gearmotors and, by extension, the wheels, providing a power boost when needed.
Driving in comfort Shadow Hawk engineers took a nontraditional approach to positioning the driver seat and console. They start with the goal of putting the driver’s eyes at a specific height and location to get the best view through the windshield. So the seat is mounted in the proper place, but it, along with the console and pedals, can be adjusted to fit the driver.
The modular seat can be sized for almost any person, with driver-controlled webbing and air bladders providing a custom fit in terms of width, length, and depth. The seats mount on an air spring for additional shock absorption, and are heated and ventilated. Two-door STVs have two seats, while four-door versions carry an additional two seats in the back. An optional fifth seat fits between the two rear seats. Seats can be upholstered in leather, cloth, canvas, or synthetic materials. There’s also almost 30 ft3 of storage behind the seats, and the rear-seat bottoms fold up for more cargo.
The console or instrument panel is actually a collection of LCD touchscreens. The driver and front-seat passenger decide what goes on each screen, and options include nav data, engine and suspension gages, Internet feeds and pages, and views from one or more of the 12 day and nighttime (infrared) cameras mounted on the front and back of the STV. The cameras do away with both blind spots and rearview mirrors, while two IR cameras looking out from either side provide security day and night. Every control knob has a different shape or texture, so drivers can quickly learn to use them without having to glance down at them.
The interior is also completely waterproof. According to the company, you could flood the interior and the screens and controls would still work.
**As of March 2013, no Shadowhawks have ever been built.