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simultaneous translatory and oscillatory reactions as these modes of response are coupled . This coupi ing increases with height of the c . g . ( dimension b ) . Thus reductions in the distance between the rider / ATV c . g . and the " spring center " of the tires ( near the ground level ) will be beneficial . Lowering of the combined c . g . will result not only in reducing effective applied inertial forces in turping , acceleration , and deceleration , but will also increase tractability by decoupling transla tory and oscillatory degrees of freedom . This assumes that the spring force / c . g . placement remains balanced . However , in actual practice , several factors serve to disturb this idealized situation . The c . g . of the overall system must include the contribution of the operator , whose weight and body dimensions are large with respect to those of the machine alone , and furthermore they are not standardized for all operators . The operator ' s c . g . will shift significantly in placement about the c . g . of the machine , thus causing rather major perturbations in the location of the system c . g . Intentional weight shifting to control the machine will result in beneficial shifting of the system c . g . , but on occasion , this fluidity of the c . g . will be detrimental to . the control of the machine .

Inertial forces acting on the system c . g . are responses to external forces . The addition of suspension damping units , such as the addition of front spring shock absorber units , serves to lengthen the time duration of sach externally - applied loadings , by allowing for deflection of the suspension . Thus , the peak magnitude of inertial force will be spread over a longer time period , rendering the machine mich more controllable when encountering . rough terrain or obstacles .

Turning Dynamics

The summing of the various forces related to equilibrium of the machine and rider in executing a turn is readily performed . The factors contributing to the instantaneous stability state such as friction between the tire and the ground surface , the centrifugal . " force " on the rider and on the machine and the effect of shifting c . g . , due to rider motion about the machine , are readily calculable . However , the number of variables may render such calculations relatively meaningless in that no arbitrary set of conditions will represent the range of all possible combinations . Thus , an empirical approach to design may be the more appropriate approach . Certain factors , of course , may be intuitively worth pursuing , such as lowered centers of gravity .

The large directional stability of the machine results from certain factors inherent in the conventional configuration of 3 - wheeled ATV ' S . The lack of differential between the rear wheels , coupled with the extraordinary traction offered by the tires , causes the rear wheels to maintain a straight line . This directional stability is sufficiently large that it may resist attempts to turn by turning the handle bar . Turning may be readily achieved by differentially weighting the rear