MCN Fleet: The Street Twin's fantastic plastic
Over the past forty years plastic parts have become the norm on Motorcycles. Fairings, clock surrounds, mudguards, coolant tanks all now go unnoticed. The material was once treated with contempt but for the large part it’s now accepted, except perhaps on engine parts.
Whenever I point out the plastic sprocket cover, ignition and alternator covers on the Triumph Street Twin to other motorcyclists there’s a moment of disbelief quickly followed by some tapping to check I was telling the truth. Their second reaction is say it's “cheap” but there’s a little more to it than that.
Plastic is as much about reducing weight as it is cost. Last year the Fraunhofer research group produced a test engine (based on a BMW F800 motor) with a plastic barrel (but with a steel liner) and reduced the weight of the original aluminium component by 20% without additional cost. Admittedly the three plastic engine covers on the Street Twin are baby steps (and don’t do much to reduce the bikes overall weight of 192kg) but it doesn’t take a genius to work out the potential of the material, sub 50kg superbike engines would become easily achievable.
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