Cycle News is a weekly magazine that covers all aspects of motorcycling including Supercross, Motocross and MotoGP as well as new motorcycles
Issue link: https://magazine.cyclenews.com/i/125877
U2 !I DQ • DQ 1111 g Marsee Magnum Monocoque ;... g ~ f'- O"l ~ f'- .Q.) ... .a E .... 0.. Q.) - Q.) III rn i: a: o ~ Z d: > > a: d: o ... > uJ a: o :l: III uJ .J a: d: J: o > 1Il III ________ o ... o 0. J: Th e sand-cast magnesi um frame elim inates many of the bo lt on components found on a conventional mach ine: gas tank, rea r fender brackets, etc. By Jack M angus The motorcycle has been basically t he same in design practically SInce its beginning. The same old tubular frame, high (forward) mounted fuel tank, spoke wheels, etc . The Japanese with all their innovative ability have not. with the possible exception of Yamaha's mono-shockers , changed the basic chassis even though The seat lifts up to expose t he gas cap and tail section bolt heads. they have made super engi nes at a most reasonable price. Rex Marsee , a 36 year old Smyrna, Georgia resident. set out to change the basic motorcycle chassis several years ago. With a solid background of racing experience in just about every form of motorsports, "Tve raced go -karts, boats, formula race ca rs and motorcycles." Marsee set up a list of standards that his design would meet. "I set forth some rules for myself: a) Integrate as many components as possible. b) Keep it simple. c) Make it esthetical . d) Make it easy to manufacture. I wanted to incorporate safety by eliminating bolted on components that would fall off for various reasons and I also wan ted a design that would give more padded area where the human body comes in contact with the motorcycle . By eliminati ng brackets that hold on components such as fenders, air cleaners. fuel tanks, oil tanks. etc., the design would lessen the chances of injury in a heavy crash." Also of great concern to Marsee was the utilization or elimination of wasted space such as the underside of the fuel tank area. which normally shrouds the frame tubes . and the poorly utilized section under the seat. Tubing. according to Marsee, is poor utilization of space since the inside of tubing is a void. Other things considered were the lowering of the center of gravity and the removal of excessive weigh t, . Thus the birth of the Marsee Magnum Monocoque. "At first I considered a welded or riveted unitized frame, b ut in mass Marsee's photo util izes Kawasaki wheel components, worn out Amacos, and a lo ng swing arm of its own. 26 production the price would be prohibitive . The logical solution was a one p iece casting of light alloy metal. Designing such a frame was very difficult since mold relief angles are critical. After much research on castings, h undreds of d rawings, and a few costly failures, I finally achieved a workable design of light weigh t (21.3 pounds) . the Magnum:' The casting of the Magnum p ro to ty pe is, accq;ding to Marsee, in crude form. "Dohler-jarvis of Toledo, Ohio, one of the largest die casters in the wo rld , studied one of my castings and stated that.production weight could be as low as 12 to 15 pound... Manufacturing possibilities are super!" Marsee , whose design background lists the fact that he designed the second monocoque sports/racing car chassis ever built in the U.S. , feels that the Magnum chassis can be produced at a competitive price. "I feel that $40 per frame at 15 pounds per unit and in quantities of 10 ,000 annual units is a practical figu re . That's ammortizing mold cost ove r the first 10,000 unit s, The sw ing-down eng ine cradle pivots on the sw ing arm bolt.