Technology: Rear

Technology: Rear  Technology: Rear


Motorcycle Suspension must be prepared for all sorts of forces and bending moments. This is especially true for heavy-duty swing arm.

When Charles and Lizzie pack up their belongings to the motorcycle, says half the world: your children, because then the place is storm-free, the neighbors, because Charles fails dreaded barbecue, and the tire dealer, because Karl has to install on his motorcycle holiday new tires.

Just for the back wheel in Charles travel steamer all no fun anymore, because the fun-loving couple with diets not care, has Liesel like the whole household is packing up the vacuum cleaner, and Karl on the way back to Bolzano still fast the Valpolicella supplies for the next barbecue bunkers. Makes the bottom line is half a tonne, moving nimbly from Charles, also from large bumps do not stop and the battered swing it almost makes the straddle. Why?

To answer, we provide a fully loaded tour athletes (Suzuki Bandit 1250 S) on the scale and calculated using the leverage of the forces and torques to withstand the design must, for not only the large axle load of more than 250 kilograms, but the extreme leverage ratio between front and Shock is the bearing and rocker arms stretched to bursting point.

Before that, we can However, the technical development of the rear suspension in motion pass in review. Until late in the 1970s, two spring legs braced against the end of the swinging load of horse and rider (see development of rear suspensions). So positioned, the arm was almost free from any bending forces and had only an ordinary torsion (twisting) come up. To satisfy a simple, one-dimensional structures of square or round tubing with backlash-free conditions and a stable locking of the rear wheel to the axle guides.

Technology: Rear

Only with the introduction of central suspension with or without lever, the bending moments changed dramatically. Initially, simple yet very fitted structures of extruded profiles (see photo page 109, Suzuki GSX R 750), recognized the designers in the introduction to the wide tires with more than 160 millimeters, that only the shape of the bending moment customized profile (see development of rear suspensions center left could guarantee Yamaha FZR 1000 EXUP), the necessary rigidity and low weight.
Thus with this finding mutated the rear wings of one, component inconspicuous to a monstrous mountain of often very elegant aluminum moldings that so many GP racer would have been good to face (photo developing rear suspensions at the bottom left, Honda CBR 1000 RR).

Nowadays, these soft artisan masterpieces of the one-or two-piece molds with some sensational thin walls. The elegance, however, remains spotty with the casting surface on the track. Such constructions are cast for an unbeatable price (right photo development center rear suspension, BMW F 800 R) to produce.

Back to the question of how come the heavy loads of Bandit 1250th With a swing arm length of 590 millimeters and a maximum static axle load of 270 kg is created between the rear axle and center of rotation of the deflection of a lever ratio of one to 2.9. If after Adam Riese a burden on the pivot point of the Umlenklagers of 781 kilograms.

The elegant sliding on flat asphalt course. Charles and Lizzie but thunder along with their Valpolicella stock on the Brenner motorway verdellten jagged gene are home, at full acceleration and a maximum dynamic axle load 426 kg on the rear axle.

In that brief moment, a peak load is increased by up to 1232 kg at the pivot point of the Umlenklagers. This corresponds to 2.6 times the gross vehicle weight of the Bandit 1250th

This extreme load may even catch a directly hinged strut, but it makes the necessary extremely hard spring is a very high absorption rate.

Overall, a package that also prepares issues in the vote and the rocker extremely stressed, what with the long-term test Yamaha XJ 600 S even led to the break.

Much smoother does matter when the shock does more lift and thus is able to operate with a softer spring. And that’s the link system makes it possible. It the lever ratio is reduced to about two to one. This means that content at 120 mm rear wheel travel the shock absorber with 60 mm stroke.

Due to the change in lever position can be reached by a progressive Feder-/Dampferwirkung deflection systems. An example: Up to about half the suspension travel, so roll when the motorcycle without a great burden on the asphalt, says the suspension is soft and sensitive, because now the shock with a short leverage short stroke (five millimeter stroke at ten millimeters rear wheel travel ) does, and thus, the spring is compressed less strongly.

Immerse the motorcycle through a bump on the back until about 100 millimeters, diminishes the leverage (progression). Then have the damper piston and spring (6 mm stroke at 10 mm of travel at the wheel) can be applied with more force. This progression (in this case 20 percent) protects against the suspension to stabilize the bike and on bumpy tracks or at athletic speedy bends.

Depending on the type of motorcycle and purpose, the progression curve is flat (slight mid-range machines) or strong (Motocross machines). That for modern motorcycles, even at full acceleration and the front wheel off the rear suspension barely submerged, is caused by the tilt of the wing and the arrangement of the chain drive.

In combination, this results in so-called pitch compensation, ie its anti-dive effect or anti-Squad. But that’s a whole different story.

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