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/612546
MUGEN SHINDEN YON RACER TEST P62 EXQUISITE ELECTRIC EXCELLENCE W eight is an E-bike's biggest enemy, with the massive battery pack needed to power the 2015 TT Zero-winning Mugen Shinden Yon around one lap of the 37.73-mile Isle of Man TT course at racing speeds dominating its architecture. So to counter this, designer Kunio Yoshimi has created a slim, aero-friendly, twin- spar chassis which, like the swingarm, fairing, "tank" shroud and mudguards, is made from carbon fiber, and was cured in the company's own autoclave oven in its Tokyo HQ. So too was the carbon battery pack casing with Kevlar- reinforced edges and joints that are slotted inside the frame, but it doesn't function as a load carrying component. The lithium-ion pouch cell batteries are supplied by the team's principal spon- sor Hitachi through its Maxell subsid- iary, and are air-cooled via an internally ducted system incorporated in the bodywork. The batteries take five hours to recharge from zero to 95 percent capacity via a 240V power source. Mounted horizontally beneath the battery pack is the liquid-cooled controller/inverter developed in-house by Mugen, which acts as its E-Super- bike's ECU in controlling the current supplied by the Maxell batteries to the oil-cooled three-phase brush- less DC motor. This was also entirely constructed by Mugen itself. In order to save weight further, the casing housing the rotor that is the motor's sole moving part was machined from a solid magnesium billet—a costly process which took three entire days of CNC time. Unlike on the world's fastest E-bike, the U.S.-built Lightning LS-218 or indeed Honda's own proto- type RC-E, the motor is not incorpo- rated in the swingarm, but is mounted separately low down beneath its pivot point, in the optimum location for ideal handling at the rear of the converter. Mugen officially quotes the motor as an "over 370-volts" package, but in fact it's understood that this exceeds 400V, making the Shinden Yon the most power-packed E-racer yet built—the Lightning by way of contrast has "only" a 380V motor. This allows the Japanese bike to produce more than 148 bhp at the output shaft, say Mugen engineers, running at 8000 rpm, with a constant massive 220Nm of torque delivered from one rpm upwards. This is transmitted to the rear wheel via a direct single-speed transmission with gear-driven primary reduction and chain final drive; there's no gearbox, as its Victory/Brammo rival has. The Mugen's carbon fiber frame supporting this electric power pack- age carries it quite far forward in a fairly rangy 58.4-inch wheelbase, whose length is presumably aimed at encouraging stability, reducing wheel- ies under acceleration thanks to the massive torque, and simply providing more real estate to position as many all-important battery cells as possible. But with a significant 55/45 percent forward weight bias, the Mugen's Two TT wins in three years with these bikes. Not a bad strike rate!