Can the DUSTBIN (for road racing)

Moto_Guzzi_racing_dustbin[1]In 1957 dustbin fairings were banned from road racing, in 2009 some people think it’s a good idea to bring them back- they are seriously mistaken.

There are many debates about why the dustbin (AKA “garbage can”) fairing was ruled illegal in ’57. The reasons range from aesthetics to politics but one of the undisputed reasons is that several crashes were attributed to the dustbins and their negative effect on handling- and that was on a 1957 motorcycle! What made the dustbin fairing dangerous for 50’s era racing motorcycles makes it suicidal for 2010 era racing motorcycles.

Old
From my office desk I can see my Grandfathers (Circa early 1960’s) 125cc Grand Prix motorcycle, this race machine was state of the art for the era. Though 125’s have the slowest top speed they often achieve the highest apex speed. 125’s are designed with very aggressive geometry to be the quickest steering and best handling bikes on the grid. Want to understand the ultimate handling abilities of motorcycles from a by-gone era? Look to 125’s.

My Grandfather’s 125 looks old, old tires, old steering angle, old Cg, old suspension everything looks old- because it is. The steering rake is 26.5 degrees the trail is more than 100mm, the tires have virtually no profile and the Cg looks lower than any modern motorcycle I have ever seen and this was one of the best handling motorcycles of the era. This “razor sharp” 1960’s Grand Prix motorcycle would be considered a slow steering street bike by today standards- it is all relevant to speed.

New
As motorcycles become faster, so must steering. The faster you ride a motorcycle the less time you have to do… well… everything. Speed compresses time. For a given bike to go thru a series of corners faster it must brake harder, steer quicker, transition faster and do so ideally with the same amount of rider input as before. Since the beginning of motorcycling every part of the motorcycle has evolved to allow the motorcycle to turn faster with less effort. Since the 1957 ban, rake has steepened, trail decreased, Cg raised, wheelbase shortened and tires profiles optimized. Modern motorcycles turn significantly quicker with less input than they did “back in the day”.

Racing
Racers push the limit, that’s what racers do and the “race line” is no exception. Racers enter a typical corner inches from the outside edge of the track, ride an arch to the apex then again to the outside edge of the track on exit. They do not just steer this arch changing trajectory at will like you do in your family car, this is the consequence of carrying the maximum speed possible thru a corner. This optimum line is duplicated by nearly every racer, ever corner, every race, it is the limit and there are only millimeters of cushion between being on line and running off the track.

When the best racers in the world arrive at a track with winds in the 15-25+mph range a modified fairing can be fitted to their bike. This fairing has less surface area, often achieved by drilling a series of holes in it. The holes reduce the overall area and help balance the Delta P (pressure drop) across the fairing caused by a side wind. This pressure differential creates a very noticeable force on the motorcycle sucking the fairing into the low pressure area opposite the direction of wind.

Remember motorcycles turn by leaning and modern motorcycles turn/lean very easily. Take a modern motorcycle and add a large side area or fairing to it and it will be subjected to forces beyond the rider’s control. Stretch that fairing fore and aft the wheels and you have now increased the leverage of that force and effect. Add additional height and now the fairing is subject to even higher wind speeds that have an even greater lever to lean and pull the motorcycle. More frightening, the rider can only overcome the unwanted change in direction by turning the motorcycle towards its new trajectory as to counter the lean initiated by the wind. This is a very counter intuitive maneuver that takes additional time and real estate most racers do not have.

Cigars and Toothpicks
Even straight line instability can be the experienced (no need for side winds) if the motorcycles center of pressure is too far forward ahead of the Cg which is typical to dustbin style fairings (with no tail). There is a great simple explanation of this in the “Worlds Fastest Indian” (highly recommended). The instability caused by this mis-calculation is even an issue at Bonneville where riders only go straight, have miles of course and can’t even find anything to hit. If Bonneville was 24’ wide and lined with stone walls streamlining would be banned- and so it should be at the IOM.

Electric racing is still racing
There is a place for streamlining. Our joint venture with Bajaj has identified aerodynamics as a project priority and one of the best methods to achieving greater efficiency and range in our project. The original C1 spent time in CFD and actual wind tunnel testing, by no means am I opposed to improved aerodynamics. As efficiency is such a component to electric racing it is easy to see why someone may think this is a good idea but I am certain this same person has no modern day racing experience.

Personally I have ridden at pace at, Willow Springs, Las Vegas and Miller Motorsports; tracks that get periodic winds. I have been blown of track several times, sometimes from a tailwind at the end of the straight, other times at corner exit. I can personally attest that in every case the bike would have been more out of control if it had a larger fairing- suicidal with a dustbin.

I hope the other manufactures and team owners will stand with me and personally elect not to race the IOM with the antiquated dustbin fairings. As our rider Mark Miller recently said: It’s war out there, this is not some college HPV project.”

MC

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