Acceleration comparison

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Acceleration comparison

Acceleration comparison
Strip poker

If you want to tear something at the traffic lights or on the drag strip, you need good cards. But even more important: good nerves. Otherwise the best hand is of no use.

Stefan Kaschel

11/29/2001

Seeing yellow and letting go of the clutch is practically one thing. Not gently, gently, well-dosed. No, just let it go. Because the enormous torque of 315 Newton meters is completely sufficient. And until it reaches the rear wheel via the monumental primary drive and the special dragster gearbox, the ten-inch wide tire filled with only 0.4 bar of air in specially applied adhesive behind powerful swaths of noise develops grip and the G & R dragster catapulted forward, only those fractions of a second pass in which the traffic light jumps from yellow to green. It depends on the exact timing of the sprint on the quartermile. Here, where minimal time units are decisive for victory or defeat, experience is required. And coolness.
“Actually, everything is decided on the first 60 feet,” says Gunther Sohn, explaining the dragster pilots’ recipe for success. He should know, after all, he finished second in the TopGas Euro Series last season (see page …). And that’s exactly the right thing to do together with MOTORRAD on the Hockenheim dragstrip to get a wide variety of Suzuki motorcycles GSX-R 1000 about the Kawasaki ZX-12R, the Harley-Davidson V-Rod, Yamahas Vmax and the KTM Accelerate the LC4 640 Supermoto to the maximum. The immediate occasion for the sprint gathering: the new Harley V-Rod. A motorcycle with a cruiser outfit and an athlete’s heart. Built to accelerate. An eternally long wheelbase of around 1.70 meters, low center of gravity, fat rear tires. Similarities to Sohn’s dragster cannot be overlooked.
But then: measured 116 hp, around 365 kilograms live weight with an 80-kilogram driver. In terms of power-to-weight ratio, others look better. A Suzuki GSX-R 1000, for example, with real 153 hp and 280 kilos including driver. That’s getting closer to the matter. Or the most powerful production motorcycle, the ZX-12R. It presses 175 hp on the test stand roller, but also weighs significantly more, while the beefy Vmax is designed similarly to that V-Rod and the lively KTM only releases 49 hp, but with 230 kilograms including the driver it is the lightweight in the field. So much for the key data.
But which factors play the decisive role in the run to the last tenth? In theory, the physicist Sir Isaac Newton recognized the basic law of mechanics as early as the 17th century with the formula F = m * a, according to which the acceleration of a body depends on its mass and the force acting on it. Consequently, with motorcycles, the vehicle weight and the tractive effort on the rear wheel dictate the ability to sprint. The tractive effort in turn is calculated from the torque of the engine, the ratio in the individual gears and the radius of the rear tire.
But that’s only half the battle. In the daily sprint from traffic light to traffic light, no wheelie bar protects against backflips. Rising front wheels remind the down-to-earth pilot to be prudent not only when taking off, but also when changing gears. The dynamic wheel load shift, which then limits the ability to accelerate, depends on the height of the center of gravity and the wheelbase. Ultimately, clutch metering, throttle response and the engine’s flywheel also play a role. Because of these factors, normal drivers do not succeed in reproducing the values ​​that professionals conjure up on the asphalt.
Even Gunther Sohn, who under competition conditions with his infernally loud G & R-bullet, which reaches 100 km / h after 1.0 to 1.2 seconds, struggles with the pitfalls of high-volume technology in the ZX-12R and Co., although they are only around 40 km / h fast in the same time. Take the Suzuki GSX-R 1000 as an example: the combination of high performance and low weight turns into a tightrope walk during a hot ride on the drag strip. “The clutch is very rough, the front wheel is constantly rising.” Super times cannot be achieved straight away. Karsten Schwers, who is responsible for the acceleration measurements at MOTORRAD, also has a lot of trouble with the GSX-R. »Because of the relatively small centrifugal mass, the dosage of the clutch is always a problem. Do you like to pluck? or slip through. In addition, you just can’t keep the front wheel on the ground. Not in first gear, and when you switch to second, the GSX-R climbs again. If you don’t know that, you get scared and turn off the gas. “
The fact that Karsten accelerates the lightweight 1000 to 100 km / h in 2.8 seconds is worthy of all honor. At 9.9 m / s2, it is in the range of what is physically feasible with normal motorcycles. This is also proven by Kawasaki’s ZX-12R power bike, which covers exactly the same time. “And that,” says Karsten, “is much easier to accelerate. More weight on the front wheel and, above all, more centrifugal mass! “This requires less starting speed, makes clutch metering easier, while the more favorable weight distribution means that the front wheel” rises, but not nearly as much as with the GSX-R “. Once the start has been made, the only thing left to do is not to roughly miss the optimum switching point. An assessment that Dragster-Pilot Sohn shares unreservedly. The reason for the rapidly rising front wheel of the two: From around 60 km / h, below that the clutch is not engaged anyway, up to 120 km / h pushing over 3400 Newton tractive force in first gear ?? more than the force of weight, and only that can be transmitted by the rear tire. So it’s a fine line.
As with the KTM. Once you really drive, the maximum pulling force of 3080 Newtons is already reached at 40 km / h, which is also far more than the rear wheel can transfer to the asphalt. Shortly afterwards, however, the pulling force shrinks dramatically. Nevertheless, it is important to turn the briefly translated first gear to the speed limit in order to find connection in the second at the maximum of 1900 Newtons. Even the professionals fight in vain against another problem: the vehement rise of the front wheel, which can only be mastered with careful metering on the throttle and prevents a better time from zero to 100 km / h. 4.7 seconds ?? more is not possible. It sounds paradoxical, but a significantly longer first gear ratio and narrower steps would do a lot more.
Exactly the right moment to push the V-Rod and Vmax: strong, long, heavy. Too heavy. The old dragster wisdom that every kilo costs time comes into play here. In absolute numbers: 3.6 seconds for the V-Rod, 3.3 seconds for the Vmax. So they don’t come close to the top times of the GSX-R 1000 and ZX-12R. The 1200s, the V2 of the Harley and the V4 of the Vmax, have enormous tractive power on the rear wheel due to the short first gears and the beefy torque. But when changing gears at 96 (Harley) or 80 km / h, in contrast to the considerably lighter Kawasaki and Suzuki, both suddenly fall into a deep hole.
Nevertheless, both have a special quality: With no other type of motorcycle is it so easy to set good times straight away and to reproduce them. Get on, accelerate, feel good. Instead of striving towards the sky with the front wheel, both of them scratch their hooves because of their favorable ratio of long wheelbase and low center of gravity. And slippage on the rear wheel not only looks good, but is the daily bread of the drag driver, because the front wheel placed far forward in the flat fork allows the load to run reliably in a straight line. Juggling with the clutch is hardly necessary.
The fact that the V-Rod cannot beat the old fighter Vmax in sprints up to 100 km / h or beyond does not leave Harley-Mann Sohn in peace. A Dyna Super Glide Sport pepped up by him with a big bore kit is supposed to fix it. Son promises 132 hp, on the rear wheel. And a whopping 183 Newton meters at 4250 rpm. With a roar, the Dyna rushes down the straight line of the forest ?? and shows what a difficult balancing act these excess acceleration are, because the clutch cannot cope with this torrent of torque and slips. 3.5 seconds to 100 km / h ?? more is not possible under these conditions. The Dyna shows potential up to the 180 mark. She distances the V-Rod (10.6 seconds) with 9.5 seconds and loses only 0.2 seconds on the Vmax despite the clutch problems.
The impact of performance and aerodynamics beyond 100 km / h is shown by the values ​​of the GSX-R and ZX-12R and even more clearly by the times that Max Biaggi achieved with his 500cc Yamaha. It takes 6.1 and 6.2 seconds, respectively, for the civilian athletes to reach 180 km / h, while the Italian accelerates to 200 km / h in 5.9 seconds. But who? listen and be amazed? starts in second gear because he too would find it difficult to control the rising front wheel in first gear. And it takes a whopping 3 to 3.2 seconds from zero to one hundred. Even if he gambled very high in the game with the clutch.

The full throttle bacillus

Ever bigger, ever stronger, ever faster: Gunther Sohn, born in 1956, has been infected with the drag race bacillus since his first race in 1994 at the All American Days at the Nurburgring. At that time, the enthusiastic Harley rider, who a year earlier with his company G & R (phone 06341/960117, www.gr-sohn.com) and since then has offered technology for Harley and Buell (for example big-bore kits with TuV), with an 80-hp Harley. “And then you want you inevitably more and more «is how he describes the typical dragster career. Fortunately, in addition to the Super Street Bikes class, which is mainly based on Japanese four-cylinder engines, the scene also has a special Harley counterpart. In the “Modified Harleys” (displacement restriction to 2065 cubic centimeters), Sohn drove successfully for a number of years and was the first to make the quarter mile in under ten seconds. Reason enough to move up to the Super Twin TopGas class in 1999, the highest thing that can be done with a slightly Harley-looking dragster. The frame, built by Kosman and modified in-house, connects a 1.85 inch wide front wheel rim with the huge nine inch wide rear wheel at 1.70 meters, the total length (with wheelie bar) is 3.70 meters Meters, the weight with a “two-liter tank full to the brim” is 205 kilograms. The load is accelerated by a 2730 cubic centimeter V2, in which the 117 millimeter pistons cover 127 millimeters of stroke, while the 41-series Mikuni racing carburettors take care of the mixture formation. The result: 265 hp at 5850 rpm and a maximum torque of 315 Nm at 4600 rpm. Anyone who thinks that they are difficult to dose with the throttle hand is completely wrong, because the throttle hand of a TopGas pilot works digitally. “There is only full throttle,” explains Sohn. “At the start and afterwards. When the clutch is pulled, the speed is automatically limited by a contact. Only when the clutch clicks does the engine run at full speed. Then the button on the left end of the handlebar is used to shift up to fifth gear, under full load with air pressure. Not even the ignition is interrupted. ”A special dragster gear with extremely relief-ground gears is necessary for this feat. With the result that Sohn cannot simply disengage, but lets his device roll out after the finish line. And it is much more comfortable than many a pilot in the dragster premier class, with the top fuelers. After the finish line, they slow down so vehemently with a parachute that the retina sometimes detaches from the eye. And that is then the highest degree infection with the full-throttle bacillus.

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