Cycle News - Archive Issues - 1980's

The Trihawk layout has two wheels in front and a single wheel in the rear. The front wheels drive and steer the vehicle. the vehicle. Bob took an immediate interest in the project. Having engineered the suspensions for factorysponsored IMSA Volkswagen Scirocco race cars, Bob was well aware that the front wheels of those racers were dealing with virtually all the accelerating, braking and steering chores.· Lou's proposed front-wheel drive three-wheeler suggested a vehicle similar to Bob's race Sciroccos, but with a lone third wheel. A third wheel to support the bodywork, rather than to deal with the cornering forces. Bob McKee went on to construct the first Trihawk prototype in 1981. Wanting a low center of gravity, this vehicle made use of a flat-four, liquidcooled Subaru engine and drive line. The results were more than promising: this prototype Trihawk was capable of astonishing times through the slalom course, and could generate impressive cornering forces on the skidpad. Unfortunately, in a production sense, the Subaru engine proved unavailable. Volkswagen, with their time-honored flat-four, was contacted - and was similarly unwilling to provide engines for the Trihawk project. The French automaker, Citroen, was found to be producing an aircooled, flat-fourengined, front-wheel drive auto with an appropriate driveline. Surprisingly, Citroen proved enthusiastic about the project, and was willing to make available new engines and transmissions - as well as offering technical assistance for adapting the powerplant to the peculiarities of the Trihawk. The engine was found. The next step was the appearance of the vehicle. For the Trihawk to sell in any significant numbers, this would be every bit as important as the function of the chassis. David Stollery (former GM senior design engineer, and later, director of Toyota's west coast design center) was asked to produce a sleek body for the Trihawk. Stollery created a futuristic and very aerodynami.c shell for the Trihawk, giving the vehicle superior performance owing to its slippery shape. Lou Richards decided that the shape was a bit too futuristic - and was looking for a more conventional, jaunty and sporty looking vehicle. Stollery's design was scrapped. After many hours of haggling at the design table, a compromise was reached; the result being the current styling ofthe Trihawk: an open-air, traditionallystyled roadster. In late 1981, a Citroen-powered Trihawk was shipped to France for evaluation. There, before the eyes of the President of Citroen (and his engineering staff), the Trihawk proceeded to post record times on the Citroen slalom course. Eyebrows were raised. Citroen was impressed. , •Thenew Trihawk was subsequently analyzed in a wind tunnel, and was found to be less than aerodynamically ideal: the bug-eyed headlights, exposed wheels and fenders, and protruding roll bar all conspired to provide excessive drag at speeds above 90 mph. Not too surprisingly, speeds in the mid-90s represent the observed top speed of the Trihawk - even when experimentally fitted with more powerful engines. This compromise of performance was judged acceptable for the vehicle's jaunty styling, and Citroen - still optimistic - assigned four engineers to Trihawk to assist with durability testing. In early 1982, Trihawk located a production and sales facility in Dana Point, California, with the first production Trihawks offered for sale in the spring of that year. Thus far, the Trihawk has been sold and promoted strictly on happenchance and wordof-mouth; virtually no money has been spent on advertising. To date, nearly 75 Trihawks have been built and sold from the Dana Point headquarters. What is a Trihawk7 A casual glance at a Trihawk gives the impression that the vehicle was cobbled from the parts bins at the local auto salvage yard. The front has a frumpy, roadster-ish appearance, while the rear tapers back to a sleek, futuristic point. Wide set, bug-eyed headlights protrude above gangly, exposed front wheels. The Trihawk reminds you of something . .. and for the life of you, you can't remember what. A Science Fair project built in Aunt Emily's garage? A counterculture vehicle, furtively assembled by campus radicals? A three-wheeled Frankenstein Monster? On close examination, the Trihawk is a completely different story. Fit and finish of the body parts is near perfect; clearly not the results of a home-built kit-car project. A sleek, sloping windshield rakes back over the padded dashboard. A full complement of VDO instrumentation monitors engine activity, and the locking glove compartment is handsomely embossed with the Trihawk logo. The interior features comfortable sports-car bucket seats, and a threepoint inertia reel seat belt is solidly anchored to a stainless steel roll bar. The floor is carpeted, and a flip-up hatch reveals a modest - but carpeted - trunk. Passenger accommodations can only be described as plush. The front of the Trihawk is covered with a fiberglass cowling, which hinges forward to reveal the engine, making access for maintenance and service a snap. And yes - about that engine. The powerplant is lifted from the Citroen GSA, and is a l299cc, air-cooled, horizontally-opposed SOHC flat four. Curious about the design are the onepiece connecting rods, fitted to a pressed-together crankshaft. A crank The Trihawk's hood pivots forward to reveal the 1299cc air-cooled Citroen opposed four-cylinder engine and transaxle. assembly such as this typically makes use of roller bearings, but in this case one-piece circular plain bearings are employed for the rod's big ends. The crankshaft, rods, bearings, pistons and sleeves are balanced at the factory, and are sold as a uni t for service: no replacement of the individual parts is possible. The cast-iron cylinders are finned for air-cooling, and are notched to seat into the cylinder head. The heads sport pure-hemispherical combustion tchambers, which resist detonation owing to the curious caved-in shapes of the piston crowns (in fact, the tops of the pistons look like a cake that fell). The engine is decidedly oversquare, with a 79.4mm bore and 65.6mm stroke. With a moderate compression ratio of 8.7: I, the engine will run on any grade of gasoline. A single camshaft is mounted in each cylinder head, and each cam is driven by its own rubber belt, run from the end of the crankshaft. Also attached to the crankshaft end is the cooling fan; cooling air is circulated any time the engine is running. An oil cooler is mounted atop the fan shrouding as part of the standard cooling system. Carburetion is provided by a single, centrally-mounted progressive twobarrel Weber carburetor, which is fed by a mechanical fuel pump. Ignition is fired by a distributor mounted off the end of the left bank camshaft, is electrically triggered, and sports both mechanical and vacuum advance. Exhaust exits through a dual system with a balance pipe (to keep it from sounding like a pair of twin-cylinder motorcycles), and is silenced by a pair of fiberglass-free mechanical mullers. As curious as the Citroen automotive engine may be, it adapted well to the Trihawk. It was able to pass all relevant EPA motorcycle emissions tests with only a minor tweek to the carburetor. The only change made for Trihawk use was to raise the height of the crankcase breather pipe; with the cornering g-forces created by the Trihawk, oil could slog out through the stock breather and make a terrible mess of the engine. As installed in the Trihawk, the Citroen powerplant produces a claimed 69 horsepower @ 5500 rpm. Power is transmitted through a single-disc dry clutch, and routed through Citroen's five-speed manual transmission. All forward speeds are fully synchronized, and the final drive • ratio of-4.12:l yields a leisurely 3200 rpm at 55 mph in top gear. Of course, reverse gear is incl uded in the package. The front wheels are driven by unequal length haH-shafts, with a nonlimited-slip differential. Which brings us to the front suspension. The front suspension's heritage is Bob McKee's racing experience, and features unequal length A-arms, suspended and controlled by coil-overshock units (like the rear shocks of a motorcycle). Overall the suspension is a combination of parts; some fabricated by the folks at Trihawk, as well as some stock components from Renault and Citroen. Steering is rack and pinion, and is an assembly fabricated by the same company thg.t custom builds steering ystems for Indy race cars. The front brakes are Renault discs, mounted outboard to suit the suspension loading of the Trihawk. The front suspension package is topped off with the obligatory antisway bar, which minimizes the tendency of the vehicle to roll when cornering. ' The rear suspension of the Trihawk is as simple as the front is complex. A BMW-style single-sided swingarm (borrowed from the rear of a Renault Le Car) is suspended by a single coilover shock suspension, and braking is provided by the stock Renault drum brake. All three wheels and tires are identical: Goodyear radial P185/70R13 tires mounted on 5* X 13 alloy rims. Since there's no provision for a spare tire, all three wheels are filled with a tire sealing/balancing fl uid at the factory. Linking the front and rear suspensions is a box-section tubular frame, which runs the perimeter of the body. The interior and seats are mounted low in a fiberglass "tub," which mounts within the frame. The bodywork is bolted down over this assembly to make a tight and rattle-free structure. The II-gallon fuel tank is mounted low and to the rear, and is protected from side impact by the frame tubes. For weather protection, a removable convertible top is available, and if the weather turns genuinely nasty, a pair of side curtains will transform the Trihawk into an all-weather vehicle. The heater/defroster works directly from the air-cooled engine, and can generate a ferocious amount of heat when it's cold outside. For warm weather con~tions,a pair of pop-out vents in the sides of the windshield provide a welcome stream of air. • (continued next ~ek) ' . Q'7

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