Cycle News - Archive Issues - 1990's

JOKf',I lll~ 2 &de ~~.... ~ ..f.~ l~t ~1 \11' VIWI~ .c.a~ 45.02' No atreamlinlng In rrOflt of th;s line. 8) 4302: MUdguard front.tIdIii. tI'Iln. ~ 45. C} .o.D2: ~uard r..... edge ITl3Jt.IIOgIe 20. 0) 45.07: Malt. ~ helght 150rnm E) 4S.D3: F,OfIl faIrlng not twrp'Id roar wheei~" that be the fact that his Ducati has more torque than anyone else' bike? Quick - check the rulebook!) We have said that a key rule regarding bodywork is 45.06, which states: "The rider... must be completely visible... when looked at from the side." But the important wording comes before this, with the rule saying that this is with the rider "in the normal driving position." An extended screen would be allowed even though it. partially hides the rider's head when in a racing tuck, simply beca use it can be said that such a tuck is not "the normal driving position," whatever that might be! At this point, if you are still arguing with the scru tineers, I would say you have a problem. The next big hurdle for the air is the widest part of the vehicle: the rider! Unfortunately, on a modern road-racer this mean a center of pres. sure forward of the bike's cen ter of gra vity. Illustration 3 Ride,s SUIt - caption This causes some instability, a bit like a dart We need to make the rear bodywork thrown backward. The rider is also usuas large as possible up to the size of the ally where the air separates (goes nonrider in order to try to get the air to relaminar in a major way - bad!), and attach, or smooth out again, after going therefore creates drag, compounded by over the rider's body. the fact that this happens at the widest This large fairing would then taper part (very bad!). gradually in the manner of a teardrop. We could try to minimize this sepaIdeally it would get the air flowing ration by getting the rider to wear properly again and prevent any further smoother leathers akin to a ski-racer's separation until right at the back of the suit, but we 'Obviously still need to bike. However, given that it has already incorporate body protection. Perhaps a been messed up by a rider of relatively combination of a smooth-skinned large cross-sectional area, this would K~vlar suit with not only armor but speprobably require a very large tailcone. cial aerodynamic padding on the back Again, the rules say no bodywork and at the sides could help keep flow can protrude beyond the back of the attached or at least minimize its disturrear tire, so that's out. The rules also bance. state that the fairing behind the seat canMany .riders already have a small not be more than 150mm above the seat hump on the back of their leathers fOT itself. And, of course, you must be able this very reason, but these humps need to ee the rear wheel - ·or at least the to be larger and matched to special helback half of it (Article 45.03). mets to be truly effective. As well as All we can do, then, is make the rear hel ping to reduce drag as air separates streamlined section as la.rge as possible off the back of the helmet, they should wi thin these restrictions. It is this sort of also give added back protection. The rear-end aerodynamics that are currentaddition of ide hump would help ly being 'experimented with by Aprilia smooth flow coming off the rider's arms and Honda on their 250cc Gf>bikes, after in the tucked position, as would extenbeing originally pioneered by Yamaha sions to the cal ves and boots - something with their droop-tailed Harada bike in already on some current Alpinestars! '96. It helps considerably if your rider is All of this additional bodywork and quite small so the droop-tail piece can rider padding has a major benefit that be tailored to his physique. But he might mitiga te any problems of extra would further benefit from a special helweight or mechanical deficiency. It also met and back hump, which, while being aJlows more space for sponsorship currently experimented with, are probalogos... bly not big enough. Most of the GP We have to accept that the airflow bikes till leave the exhausts out in the will be more turbulent and will probaopen and do not extended the tail unit bly separate or stop flowing smoothly at some or all points around the rider no sideways to catch the flow off the front matter how smooth his or her clothing fairing and rider's boots, even though is. If you have ever ridden at a certain they have extended the front fairing as speed and been buffeted from side to far back as allowed (Le., to the rearside, this could well have been due to wheel spindle). the air um~venly separating from your Suzuki has followed a similar if lessback and helmet. The rules states that radical path w·ith their GSXR750 in we can't enclose a rider in bodywork-World Superbike. Suzuki also claims not that we would want to, but how else that this tail unit, by reducing the wake can we get around this major drag-causbehind the bike, stops a following rider it;lg problem of flow separation? from drafting. In all likelihood it is prob- F) <15.0:3. Rur haIJ ~ tin must bI! 'tlSibte. G) 45.03; No bodyWorit bItund rur whML (Above) This drawing illustrates the basic restrictions regarding bodywork in Grand Prix racing today. The Article number from the FIM rulebook that dictates each of these parameters follows its letter code. (Left) Return of the saggy butt: Yes, he does look stupid, but then compare Mick Doohan's outfit with Geoff Duke's! The smooth-skinned suit would include back and side lightweight foam-padding "humps" for improved aerodynamics, as well as boot and elbow extensions and a color scheme that is designed to work with the rider on the bike. The helmet features Indy-ear-style rear trip molding to cleanly separate airflow onto back hump. ably too small and short to fulfill such a claim, and it is simply impossible to fully eliminate a lower-pres ure lip-. stream no matter how aerodynamically perfect the bike is. In reality, even a larger droop tail uch (as shown in the illustrations) will not be sufficient to smooth thi turbulent wake; but it could help and, as we know, every second counts. To gain additional seconds, and top speed, it would be just as well to tuck the exhausts neatly into our tail unit. . But we should also pay attention to an equally important area of airflow that passes through the bike to the engine via carburetors or injectors and to ·the radiator for engine cooling. Only a few bikes such as the Britten V-IOOa and Taylormade Triumph have successfully raced with rear-mounted radiators incidentally, both of these raced in the same BEARS series. Yet this is an obvious way of improving aerodynamics by allowing a smaller radiator and proper internal airflow. If we added a radiator exit venturi also within our ,ear bodywork, we could use a much smaller radiator compared to the vast, triple-layer cooling cores currently seen behind most front wheels. With their exits considerably restricted by a large, hot engine behind them, they are not the epitome of good internal flow. A rear venturi would also help draw the air through the radiator (meaning smaller duets at the front) and also help to fill in the lower-pressure area behind the bike. The exhaust, if properly managed, could be able to contribute here as well. Certainly this thinking was prevalent in the mind of Kenny Roberts and Warren Willing when they were putting together the original Modenas ~. But after a relatively poor season, they have thrown the baby out with the bath water and shoved the radiator back to the front! If Team Roberts had had more development time away from the pressures of a season they may have been able to bring the bike's aerodynamics up to snuff with more work on internal ducting and the radiator exit flow. Having smaller air inlets at the front means less disruption to the flow as it is first pushed aside by the bike. There is proba bly quite sufficient air rWlning into the bike for engine breathing and cooling via the gap between the front wheel and bodywork necessary for suspension travel (rule 49.07). Certainly this is where the Yamaha YZF superbike has its airbox inlet rather than the more stylized and high-pressure duets of many bikes featuring ramair, such as Suzuki's GSXR or Kawasaki's ZX-7. These large front ducts might give character to the road ver ions but are questionable aerodynamically. Certainly in superbike the bodywork rules are even more relaxed in that the requirement is only to stick to the general shape. As long a the bodywork for the homologated road version is a close Silllouette to your race bike, then you're okay (Article 01.59). The problem for the designer here is that it might be possible to build a very aerodynamically efficient race bike but that the visually identical road bike doesn't sell because people think jt's ugly or the styling is a little too extreme for us conservative sport bikers. Aerodynamics are still a gray art, particularly when dealing with motorcycles, which shift around so much more than cars. With four wheels, and especially if using wings to generate downfo,ce, tiny aerodynamic tweaks can make the difference between being first or nowhere. With bikes, however, up-side-down wings won't work and are, at any rate, banned (Art. 45.04). So the airflow management around both bike and (just as importantly) rider is restricted to just letting them slip through the air as efficiently as possible. Often, otller criteria take on much greater importance, such as engine power, traction and weight limits. But looking closely at tlle rules and altering certain areas for small increases in speed can well be worthwhile, as long as other areas of performance and ridability are not made worse. The problem with' any of these proposals is much the same as with packaging any vehicle: Look too cIa ely at one aspect and changes made will likely compromise another area. So if we shroud the front wheel on a circuit with lots of heavy braking, the caliper and disc will overheat. And what if the small but significant weight addition of the larger tailpiece negates any benefits in improved airflow, or what if it doesn:t work because the rider is always moving around? In which case, this is all a waste of time and Grand Prix bikes next year will look just the same as this year or will they? {~ ...... l-< P... ~ 25

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