Excitement on Three Wheels

Tri-Magnum is a high-performance three -wheel sports car. It was introduced on the cover of Mechanix Illustrated magazine, and today, it's still one of our most popular designs.
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**If you've ever wanted to build a special vehicle of your own design, the Tri-Magnum plans will be an invaluable aid.  


The mention of 50-mpg fuel economy normally implies econobox driving or an expensive hybrid.  But you do not have to give up good looks or buy a high-priced vehicle in order to cut down on gasoline. Tri-Magnum is an excellent example of how ultralight construction can result in both high fuel economy and sports car performance. This motorcycle-based three-wheeler performs like a production sports car, and it still delivers fuel economy roughly equivalent to that of the original motorcycle. The key constant on performance is the power-to-weight ratio.

With 80 hp and a 1,200-pound curb weight, Tri-Magnum has a power-to-weight ratio of 15 pounds per horsepower, which equates to a 3,500-pound car with a 233-hp engine. Built on a Honda Gold Wing, a GL1800 for example, power-to-weight ratio comes in at about 10 or 11 pounds per horsepower – or roughly equivalent to a 3,500 pound car with 350 hp engine.  And if that’s not enough, there are lots of add-ons that will increase power output, including turbochargers.

The original Tri-Magnum was built around a Kawasaki KZ900 motorcycle. However, the Honda Gold Wing, especially the model with the electric reverse, is an even better choice. The Gold Wing’s 6-cylinder opposed engine as smooth as any automotive engine, it develops maximum torque at a comparatively low rpm (best for automotive application), and it’s more fuel-efficient that the original KZ900 engine. The chassis consists of a stripped motorcycle, minus the fork and front wheel, which is then attached to a VW Beetle front suspension assembly using a simple framework. The motorcycle drive train is used as is, including its lightweight and efficient 5-speed transmission.

   Tri-Magnum’s styling is both functional and in character with its aggressive performance. Slippery aerodynamics, engine cooling requirements (either air-cooled or water-cooled), accessibility to the cockpit and engine compartment, ease of construction, and safety considerations are all integrated into the design. The impact-absorbing foam-filled front bumper, which ties into the frame with massive steel members, is designed to spill air onto the body. Body lines flow smoothly from front to rear where they break sharply around taillight nacelles to create a clean separation point. The rear-facing duct on top and the two shark-gill louvers on the sides are designed to draw hot air from the engine room while cool air is ducted into it from underneath. A small electric fan, located just ahead of the engine, or on the radiator of a water-cooled machine, keeps it cool at idle.

The lift-up canopy, though exotic, is simple, functional and strong. It leaves the main body area integral for maximum strength. When the canopy is open, it presents an entirely open cockpit so you don’t have to duck under a low roof line when getting in and out. The canopy is counterbalanced with two air cylinders, the type used on automotive hood and decks, so it is easy to lift and stays up by itself. A steel framework is laminated inside the canopy for extra strength and rigidity. Seating is side-by-side, and the seat, which is contoured from head to knees, is molded into the car’s body. Passengers ride between the two front wheels for maximum side-intrusion protection. A solid bulkhead forms the rear of the cockpit where it also serves as a roll-member.

Driving Tri-Magnum is as unique as the vehicle itself. Shifting is done with the jet-fighter-style control stick that emerges from the floor between the occupants. The control stick carries the handlebar controls from the motorcycle, which are now stacked back-to-back against each other (one from each side of the handlebar) where they are within easy reach. The motorcycle clutch lever is also mounted on the control stick. To shift gears, grab the control stick, squeeze the clutch lever, then move the stick either forward or rearward, depending on whether you are up-shifting or down-shifting. The stick is connected via a short link to the foot-lever that is normally used to shift gears on the motorcycle, so the shift pattern is identical. Accelerator and brake pedals are mounted on the floor, just like those of a conventional automobile.


Due to its forward-biased center of gravity, Tri-Magnum understeers, just like most conventional automobiles. Pushed in a turn, she will float to the outside, rather than spin out, unless of course you push past its limits. During a three-wheel-locked stop, Tri-Magnum’s rear floats slightly to one side, then rights itself and floats slightly to the other side, with no tendency to swap ends. Because of its low center of gravity, which is located forward near the side-by-side wheels, the margin of safety against rollover is equivalent to a standard four-wheel family sedan. Tri-Magnum was featured on the cover of Mechanix Illustrated magazine.

See how you built Tri-Magnum’s sleek and strong body.

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