Letter From Europe
LETTER FROM Europe
Second-generation ELF
New motorcycle chassis designs are increasingly in the news in Europe of late. More and more alternatives to the traditional means of tying two wheels, an engine and a rider to gether have reached the experimental stage.
The o1d~'st of these "new wave" chassis concepts is the ELF2 roadracer, a 500cc GP bike powered by a factory Honda three-cylinder NS500 engine. Descendent of the one-liter ELFe endurance racer, the ELF2 is the brainchild of French engineer André de Cortanze. Be cause of his other full-time commit ments with Peugeot, however, de Cortanze has left the ELF2's construction and development in the hands of Daniel Trerna.
The new machine retains some of the innovative features it had last year when it was first revealed in public. But at the same time there have been some pragmatic con cessions to the reality of mo torcycling as opposed to theory which has resulted. in major changes.
Chief of these changes has been the substitution of the curious foreand-aft joystick steering with a more-conventional though still innovative hub-center design. Test riders complained of poor low-speed control and lack of response with the previous system. But the chassis less concept remains on the ELF2, with each side cover of the Honda engine replaced with special magne sium castings onto which the front and rear suspension are bolted.
De Cortaiize's single-sided front suspension is used again, with twin parallel arms and a kingpin, and a single-sided rear swingarm (Either of the specially-cast magalloy wheels can be changed in 15 seconds). But instead of the twin Marzocchi suspension units used last year. the revised ELF2 employs a pair of Dutch-built White Power shocks mounted above but on opposite sides of the engine. These more con ventional suspension units are con trolled by rocker-arm systems front and rear that are claimed to give a true rising rate. Moreover, they are interconnected across the top of the engine by a torsion bar.
i'his idea is one that de Cortanze has flirted with in the past, though never put to the test in an actual race. It is intended to have the same overall effect as an anti-roll bar in a racing car. On the ELF2, the system has three presumed benefits: Under acceleration the system counteracts the tendency of the short wheelbased (52 inches) bike to wheelie. Under braking the bike squats rather than dives. Finally, de Cortanze claims that in a corner, when G-forces try to compress both suspension units, the interconnected linkage works one shock against the other to keep the chassis from squat ting, thus maintaining optimum cornering clearance.
Thank~ to the revised suspension, the ELF2's fuel can be carried in a tank under the engine, as on the ELFe, with a Keihin diaphragm pump feeding the carburetors. Also, carbon-fiber brake discs are used. one for each wheel, with two four piston Brembo calipers mounted on the front wheel. -
Now painted a patriotic !~rench tricolor instead of the original black and red livery, the ELF2's bodywork has been refined in the ELF wind tunnel near Bordeaux. Thus a drag coefficient lower than that of any other current racing motorcycle is claimed. The bike's weight is still rather high, however, in current GP terms-around 285 pounds as op posed to a target of 250 pounds.
De Cortan~e and Trerna have plans to make the fairing in Keviar, and to introduce other weight-saving measures on the new machine. In its debut at the French GP, the bike overheated in five laps; the radiator lies behind the handlebars, and get ting enough cooling air to it may be a problem. But the ELF2 is expected to be a regular GP contestant from now on.
ALAN CATHCART
