Yamaha Performance Damper

/// Function

The actual function of the Performance Damper is somewhat hard to comprehend. On a related but much larger scale, earth quakes produce vibrations that create movement in structures that, through repetition, cause severe devastation. Video clips of bridges and buildings swaying in the throes of a big quake before collapse, demonstrate how vibrations can manifest into reverberating movement. It is not surprising that in Japan, modern buildings are now using the concept of mechanical 'chassis damping' within their architecture, to limit the impact of an earth quake by decreasing the speed and duration of the shaking. . Every structure which has an effective mass and stiffness is said to have a natural frequency. It is called a natural frequency because it is natural. Typically engineers can change the natural frequency by changing mass or stiffness. There are only 2 ways to reduce the effects of natural frequency, either by mass loading or by damping. In the performance world, mass is the enemy, so damping is truly the only reasonable option.



Body is always moving/vibrating when it is running
With Performance Dampers

In a motor vehicle, the suspension controls a lot of the elements introduced from the road using springs and oil dampers to absorb the energy. There is always some compromise in the design between 'comfort', 'agility' and 'stability'. Generally vehicles intended for high speed performance have the stiffest frames and suspension calibration to limit body roll and other adverse reactions to extreme cornering G-force and shock loads from the road surface. Cars designed more for general performance will be less stiff, offering greater comfort and agility at lower speeds. The issue with traditional shock and springs technology is they filter high frequency vibrations very well, but if you desire a stiffer ride for “sportier handling” the low frequency inputs often pass through. The problem with lower frequency is they often turn into larger displacements. Regardless of the chassis design, there is inherent vibration and movement within each structure, adversely affecting the handling and comfort that is not being effectively dealt with. Essentially the whole vehicle acts as a spring and is in constant motion. This is the premise, for the Yamaha Performance Damper.



The PD design closely resembles that of a suspension shock absorber. A 'piston-valve' connected to a shaft is positioned in an oil filled, gas pressurized tube. The ability of the oil to be displaced by the piston valve moving in either direction within this tube is controlled by a 'stack' of thin metal wave-washers that deflect enough to allow the oil to pass. The amount of deflection and consequent oil flow is pre-tuned for the application to effectively control the speed and sensitivity of the pistons travel based on the load and frequency of the forces being applied. In simple terms, the damper will resist movement initially and give way in a controlled manner, taking on the input energy which is subsequently transformed into 'heat' as it's absorbed into the oil.



Where the PD departs from a common suspension shock is in the amount of movement and the tuning required to be effective. Theoretically the piston could move up to 20mm but in actuality it moves very little, more practically in the 1 to 3mm range and in some applications the functional movement is measured in microns (fractions of a mm). To achieve the required sensitivity to such small deflections, a negative spring works in conjunction with the nitrogen gas charged oil chamber to counter the damper rod reaction force. This is the 'key' for the piston to react to higher frequency input with great sensitivity. However, it then becomes more difficult to control the lower speed movements (flex) with such a high viscosity setting, so the damper is designed to move slowly when a large amplitude input (requiring more stroke) is applied.



For tuning purposes, the PD is available with 13 levels of damping by using varying piston valves and oil viscosity. The application chart lists the dampers from a low 200N (Newton) to a maximum 800N in 50N increments which determines the pistons speed against the damping force. The selection of the correct damper is made through testing and evaluation, to meet the engineer's requirement. The piston shaft (damper rod) accepts various length 'extensions' to achieve the optimum mounting points on the chassis, where either welded tabs or special brackets are required to bolt the device solidly to the frame.



Because the vibrations resonate throughout the whole vehicle, the damping control works best when applied towards each end consequently the dampers are employed in pairs. Yamaha holds specific patents, not only on the design and application of the performance damper; the actual mounting location requirements are also protected. On automobiles, the PD can often be easily seen mounted between the shock towers above the engine. It may take a bit more searching to find the rear damper, sometimes tucked away in the base of the trunk or up under the spare tire. On snowmobiles, the dampers are being affixed ahead of the engine between the shock absorbers and out back, parallel with the rear grab bar.