Technology wind tunnel

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Technology wind tunnel

Technology wind tunnel
Windmill

Today the riders of modern sports motorcycles fight just as desperately against the wind as Don Quixote against the windmill blades in his day?

Waldemar Schwarz

08/01/2000

Just like the knight of the sad figure, one or the other motorcyclist feels today who desperately tries at higher speeds to defy the hurricane that is breaking over him? and that although his machine has a disguise. Not only does he have to cling to the handlebars, but the turbulence also gives him a hard knock on his ears. Are super athletes optimized solely for good aerodynamics, i.e. high performance? Effective wind protection and sophisticated aerodynamics are mutually exclusive?
Questions that MOTORRAD investigated in the VW wind tunnel in Wolfsburg using the example of six super athletes. The slim one stepped in the 750 class MV Agusta F4 S against Suzuki’s superbike GSX-R 750 on. In the big bikes category, the new Honda CBR 900 RR faced the revised one Yamaha YZF-R1, and in the big class met the Suzuki GSX 1300 R Hayabusa and Kawasaki ZX-12R on top of each other.
Since the air resistance is the product of the air resistance coefficient cw, which defines the aerodynamic qualities, and the frontal area A of the vehicle, the frontal area was determined first. The VW wind tunnel specialists use a technically sophisticated method (see box on page 18) to determine the area that the engine has to push through the wind. First without a driver. Nonsense, the inclined reader will think, has anyone ever seen a motorcycle ride without a driver? Wait and see, interesting conclusions can be drawn from this. Measurements with the pilot lying down and seated also follow.
As expected, the slim MV Agusta without a driver has by far the smallest frontal area of ​​0.45 m2, followed by the R1 with just under half a square meter. In third place is the CBR 900, in fourth the GSX-R 750. Not surprisingly, the Hayabusa and ZX-12R punch the largest holes in the air with their massive appearance, namely 0.56 and 0.58 m2.
If the differences between the machines are still relatively large, they shrink considerably when the driver is lying down. The difference between the MV, which is still the smallest frontal area (0.64 m2) and the ZX-12R (0.7 m2), is only 10 percent compared to 30 percent when measured without a driver. The R1, which is in second place without a driver, is now moving closer together with the GSX 1300 R (0.67 to 0.69 m2).
The situation is similar when the driver is seated. However, the MV can again set itself apart from the competition. This is due to her extreme sitting position with her upper body bent far forward, in which the driver is still lying more than he is sitting. Apart from the ZX-12R, the rest of the field from the GSX-R 750 to the Hayabusa is very close together with 0.75 to 0.78 m2. With 0.8 m2, the Kawasaki clearly has the red lantern.
More decisive than the individual values ​​per se is the percentage increase in the frontal area with the rider – therefore the measurement of the motorcycle alone was necessary. A large increase in area proves that a large part of the rider protrudes beyond the base of the motorcycle? which is not conducive to both the drag coefficient and thus the wind slippage as well as the wind protection. With its slim silhouette, the MV, which initially appears very aerodynamic, loses part of its good aerodynamic drag with the driver. It gains an impressive 43 percent when the driver is lying down, while it is only 21 percent with the ZX-12R. The increase with a seated driver is even more extreme: 38 percent of the Kawasaki are compared to a whopping 61 of the MV.
In order to definitely determine the air resistance, the driver and machine now switch from the hot spotlight of the projection headlights to the cooling hurricane of the wind tunnel, which is approaching at 180 km / h. The measuring scales mercilessly bring the drag forces and thus the drag coefficient cw to light. The drag coefficient is a dimensionless quantity that describes the aerodynamic qualities of a body. The measurement with the driver lying down confirms the statements based on the increase in area. Suzuki Hayabusa with 0.48 and GSX-R 750 with 0.49 clearly set themselves apart from the competition in terms of drag coefficient. The MV falls back into midfield with 0.51 and draws level with R1 and ZX-12R. The CBR 900 RR scores worst in terms of aorodynamic qualities.
With the driver seated, the drag coefficient of the MV increases relatively moderately to 0.56 due to the extreme seating position. But the big bikes are right at the forefront here. The comparatively lush fairings integrate the driver best and thus ensure a good drag coefficient. Above all the ZX-12R, closely followed by the Hayabusa. The Yamaha R1 is an outlier, in which the seated rider permanently disrupts the aerodynamics.
But ultimately, the product of cw x A is decisive for air resistance and thus the real power requirement on the rear wheel of a vehicle. The MV takes over with the driver lying down? and that is the decisive value at high speeds ?? the top, followed very closely by the Suzuki GSX-R 750. And the mighty Hayabusa is just behind the petite 750. But even the ZX-12R doesn’t finish far behind the others in the final sprint. With values ​​between 0.33 and 0.36, i.e. not even ten percent difference, the differences between the slim MV and the voluminous ZX-12R are leveled out.
When the driver is seated, the MV is again in the lead with 0.41, followed by the Hayabusa, GSX-R and ZX-12R with 0.43, followed by the CBR 900 RR with a respectable margin of 0.45 and the R1 behind with 0.49 whose driver is obviously hanging like a mainsail in a stiff breeze. In the power requirement at 200 km / h between the best and worst candidates in a lying position, it amounts to just 3.9 hp, but when seated it already makes a difference of 11.5 hp, with corresponding effects on consumption.
The moment of truth strikes on the street. The test subjects have to prove whether good aerodynamic qualities only ensure superior driving performance, but exclude good wind protection. Motorway travel at higher speeds is the order of the day, especially the MV Agusta. It underpins the results measured in Wolfsburg. Even folded up like the proverbial jackknife, there is considerable wind pressure on the helmet and shoulders at speeds over 200 km / h, as the disc is designed much too flat. A similar result then with a sitting – sorry, semi-lying position: The already high wind pressure on the helmet increases even further. With the driver lying down and seated, the MV requires the least amount of power to overcome air resistance. However, the MV designers have clearly subordinated the driver’s wind protection to the design.
The Suzuki GSX-R 750 is completely different: When the driver is crouched, most of the air flow brushes over the helmet and offers significantly better wind protection than the MV. The GSX-R can shine with the same air resistance, although the mirrors that protrude far allow for consideration and the indicators, which are not integrated in the mirrors, as well as the silencer are free in the wind. Even when the driver is seated, there is still sufficient wind protection. The clear winner on points is the Suzuki GSX-R 750.
The Honda CBR 900 RR, which was neither an aerodynamic miracle nor blessed with good wind protection when it appeared in 1992, continues this tradition. Even when the driver crouches deep behind the windshield, strong turbulence shakes the helmet. If the pilot changes to a relaxed sitting posture, he will also feel the turbulence on his upper body at high speeds. Driving quickly turns into exertion on the CBR. Neither the aerodynamic qualities, in which it is the bottom light when the driver is lying down, nor the wind protection are convincing. Facelift is the order of the day.
The Yamaha technicians knew about the aerodynamic deficits and the modest wind protection of the R1 (see MOTORRAD 13/1998) and have improved the 2000 version. With partial success: The modified upper part of the fairing, including the windshield, now offers the reclining driver noticeably better protection. With the pilot seated, the wind pressure on the driver’s upper body is enormous, even if there is less turbulence than with the Honda. With the driver lying down still placed in the middle field, the R1 with the driver sitting down falls significantly behind the competition. Narrow victory on points over the Honda CBR 900.
In the case of the speed bikes, the measurement of the frontal area with and without the rider indicated that they could better integrate their rider into the motorcycle and thus offer proper wind protection. In fact, the ZX-12R can completely convince in this discipline. When you crouch low behind the windshield, you are even relatively calm, and the maximum speed of over 300 km / h can cope with the neck muscles far longer than any traffic situation allows. And even with a relaxed upper body, the wind protection is so good that above-average speeds are no problem over long distances. Not surprisingly, the sweeping power bike with the rider lying down also has the greatest aerodynamic drag thanks to the largest frontal area, but the situation changes significantly when the rider is seated. The ZX-12R may not offer the best aerodynamics, but it is the absolute boss in the ring when it comes to wind protection.
In the latter discipline, the Suzuki Hayabusa cannot keep up. At extremely high speeds, significant wind forces pull the helmet even when the seated position is folded up. If the driver only sits up slightly, the neck muscles of a prize boxer are in demand. Nevertheless, the GSX 1300 R does far better than the Honda CBR 900 or Yamaha R1 in terms of wind protection. And compared to the ZX-12R, it can shine with aerodynamic qualities. It not only looks like a product from the wind tunnel, but thanks to its good Cd values ​​in the field of the much more compact 750 to 1000 cc models, it also stands out splendidly in terms of air resistance.
The result is that the balancing act between good wind protection and sophisticated aerodynamics is not mastered best by extremely dynamic appearances such as the MV Agusta, but the Suzuki GSX-R 750, which secretly takes the pole with the most successful compromise between good wind protection and proper aerodynamics Position in the field. And that, although many details are not even designed for good wind slippage.
For the remaining candidates, they can only convince in one criterion. If you are ahead in terms of aerodynamic qualities, the wind protection falls by the wayside (see Hayabusa) and vice versa (ZX-12R). And some sports bikes like the Honda CBR 900 and Yamaha R1 cannot even shine with particularly good aerodynamics. Bad airflow much too large radiators, too short and incorrectly designed windshields and many other deadly aerodynamic sins are more the rule than the exception on most motorcycles.

VW wind tunnel

VW specialists determined the air resistance of the motorcycles in the wind tunnel. The task was by no means as unusual for the car developers as it might initially appear. Are two-wheelers much more oriented towards cars than four-man bobsleds, ski racers or telephone booths? where the wind forces on the doors during a storm are simulated. All of this has already been measured in the VW wind tunnel. The determination of the frontal area is smart: a headlight several hundred meters away projects the area of ​​the object to be measured onto a screen. A camera behind it picks up the image and transfers it directly to the computer for evaluation. The experts determine the drag coefficient in the large climatic wind tunnel. A blower with a drive power of 3500 HP with a diameter of nine meters ignites a hurricane of up to 180 km / h wind speed in a closed circuit in which the measuring section is located. Scales on which the vehicle is mounted register the forces, in the case of motorcycles in the vehicle longitudinal and vertical direction, from which the drag coefficient as well as the upward and downward force on the front and rear wheels result. In addition, air temperatures of minus 30 to plus 45 degrees Celsius and a relative humidity of five to 95 percent can be achieved.

MV Agusta 4S

Anyone who wants to ride a two-wheeled beauty has to suffer. The F4 S is by far the most compact machine in comparison, but it is far from having the sophisticated aerodynamics that its appearance suggests. Nevertheless: low air resistance. The wind protection is only moderate, however.

Suzuki GSX-R 750

The moral winner of the comparison field: Thanks to the larger, inexpensive fairing, the driver enjoys good wind protection, and thanks to good aerodynamics, he also gets high performance. The Suzuki GSX-R 750 is proof that both requirements can be brought under one roof.

Honda CBR 900 RR

Close to the wind: Whether lying down or sitting, strong turbulence sucks the driver. With the modest wind protection paired with modest aerodynamics, the CBR 900 is way behind the competition. Nominated for the golden wind egg by the jury of wind faces.

Yamaha YZF R1

We understand: modified by Yamaha in terms of wind protection and aerodynamics for model year 2000, the R1 is more user-friendly. Better wind protection when the driver is lying down, but enormous wind pressure when the driver is seated. Perfect is different again.

Kawaski ZX-12 R

Catch the wind: Driving fast made easy. Regardless of whether the rider is lying or sitting, the Kawasaki ZX-12R sets the standard for sports motorcycles in terms of wind protection. Despite its aerodynamic qualities when the driver is seated, the largest frontal area increases the air resistance in comparison.

Suzuki GSX 1300 R.

Ride the winds of change: If the form submits to the aerodynamics, controversies are inevitable, with the audience and the driver. Top grades for the Cw value, only medium grades for the wind protection, changeable to windy assessments in the beauty contest.

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