with reference now to the various figures in which identical elements are numbered identically throughout , a description of various exemplary aspects of the present invention will now be provided . the preferred embodiments are shown in the drawings and described with the understanding that the present disclosure is to be considered an exemplification of the invention and is not intended to limit the invention to the embodiments disclosed . fig1 illustrates a trailed mower 100 that is comprised of a frame 110 supported at the rear on two tires 120 , only one is illustrated as this is a side view , and at the front by a hitch 102 of a tractor 104 . the position of the wheels 120 is fixed in relation to the frame 110 such that the height of the frame 110 from the ground is fixed . in this figure , a mowing unit 200 is in a raised transport position , with a front side , closest to the front of the frame , configured to accept crop material , and a rear side configured to eject crop material . the mowing unit 200 is mounted to the frame 110 by a linkage including parallel links . the parallel links include two bottom links 140 a , 140 b . the left link 140 a is shown , while the right link 140 b is not shown . further , the parallel links include a single top link 130 , located between the two bottom links 140 a , 140 b . in fig2 this linkage is illustrated in a partially lowered position wherein the top link 130 is connecting the mowing unit 200 to the frame 110 . the single top link 130 is attached to the frame 110 at a top link frame pivot support 133 , which is illustrated as approximately concentric with the center of the wheels 120 . this pivot support 133 can be located in other positions , its position relative to the wheels is not critical , and the present invention is not limited to any particular location for the pivot support 133 . the single top link 130 is attached to the mowing unit 200 at a top link pivot 134 by a top link ear 135 . fig1 illustrates the linkage , showing both bottom links 140 a , 140 b attached to the frame 110 at two frame pivots 142 a , 142 b , configured with pivot supports 143 , on each end of the frame 110 . the pivot supports 143 of frame 110 include apertures that align to define a pivot axis . the bottom links 140 a , 140 b both attach on the opposite end to the mowing unit 200 at two mower pivots 144 a , 144 b . the mower pivots 144 a , 144 b are configured with bearings 202 , 204 , as will be described below , as components of the mowing unit 200 . the mowing unit 200 further includes stops 206 that can be positioned in a variety of positions , as illustrated in fig2 a and 3 . the pivot joints at pivots 132 , 134 , 142 are basic pivots . any known type of bearing or bushing could be employed in these pivots , preferably comprising spherical ball joints to provide two degrees of freedom , similar to pivot 142 which includes spherical ball joint 143 , illustrated in fig3 . the present invention incorporates a novel mower pivot 144 including a rubber torsion axle assembly 301 ( see fig4 ). fig4 and 4 a illustrate the arrangement of the components of the mower pivot 144 . the outer square tube portion 308 of a traditional rubber torsion axle assembly 301 is fixedly connected to , and a component of , the lower link 140 , in this embodiment configured as a bolted joint . the mower pivot 144 is configured when the axle 300 is installed through the square tube 308 , rubber springs 306 are installed in the spaces between the inside surfaces of the square tube 308 and the outer surface of the square shape of the center section of the axle 300 . this rubber torsion axle assembly 301 is secured in position as the shaft portion 304 is mounted in the bearing 204 , a torque arm 310 is attached to the axle portion 300 of the rubber torsion axle assembly 301 and shaft portion 302 is mounted to bearing 202 . the torque arm 310 is rotationally secured to the square portion of the axle portion 300 of the rubber torsion axle assembly 301 , by the configuration of aperture 311 which mates with the square tube portion of the rubber torsion axle assembly 301 . an aperture 311 is constructed such that the torque arm 310 is reversible , and the same component is used on both sides of the mower . fig3 illustrates the torque arm 310 , positioned as shown in fig2 a , to come into contact with the stop pin 206 which is supported in the frame 200 and the support plate 208 . after the torque arm 310 contacts the stop pin 206 , the axle 300 will be restrained from further rotation relative to the frame 200 . the mowing unit 200 can be lowered , from the position shown in fig2 and 2 a , towards an operational position illustrated in fig5 , by further extending two cylinders 150 , only one cylinder 150 shown in fig5 . as the mowing unit 200 is thus lowered , the outer tube 308 will rotate counterclockwise , as shown in fig2 a , while the axle 300 is held from rotating , causing relative rotation between the outer tube 308 and the axle 300 , resulting in a compression load in the rubber springs 306 , generating a moment load at the mower pivot 144 . in fig1 the mowing unit 200 is illustrated raised into and held in the transport position by the cylinder 150 that connects to the frame 110 and to the lower link 140 . fig8 illustrates a cylinder force 152 acting on one lower link 140 , with a resultant force 148 a acting at the mower pivot 144 . a force 141 acting generally at the pivot 142 is the sum of the two other forces 148 a , 152 acting on the lower link 140 . this force will result in combined distributed loading on the rubber springs 306 . the resulting equal and opposite force 148 b is applied to the axle 300 as illustrated in fig9 where an equal and opposite force 248 a is applied from the mowing unit 200 through the bearings 202 and 204 . the free - body - diagram of fig6 shows force 248 b applied to the mowing unit 200 . in this way , the lower links 140 transfer force from the cylinder to lift the mowing unit 200 with the rubber torsion axle assembly 301 , while the upper link 130 holds the mowing unit 200 from freely rotating , via the force 136 b applied at pivot 134 . the upper link 130 will be subjected to a tensile load , as illustrated in the free body diagram of fig7 . the cylinders 150 are extended to lower the mowing unit 200 into the operating position illustrated in fig5 . as the cylinders 150 extend , and the mowing unit 200 lowers , there will be rotation between both the top link 130 and the bottom links 140 a , 140 b and their mating components on both the frame 110 and the mowing unit 200 . as a result of this rotation the torque arm 310 will move relative to the mowing unit 200 from the position as illustrated in fig1 , to the position as illustrated in fig2 a with the mowing unit 200 in a partially lowered position . in this position the torque arm 310 will come to a position where it first contacts the stop pin 206 . as the cylinders 150 continue to extend , lowering the mowing unit to the position as illustrated in fig5 until there is no load on the bottom links 140 a , 140 b , as provided by a slot 152 of the cylinder 150 . in addition , the lowering action causes rotation of the bottom link 140 relative to the mowing unit 200 which will generate a torque 146 within the axle 300 resulting from the contact of the torque arm 310 with the stop pin 206 , and a reaction force 312 a . the moment 146 is the result of compression of the rubber springs 306 . the equal and opposite force 312 b on the mowing machine associated with the reaction force 312 a on the torsion axle is shown in fig1 . as illustrated in the free body diagram of fig1 , with the cylinders 150 completely extended , there will be no cylinder force , and the moment 146 will be applied to the end of the link 140 by the axle 300 , which will simultaneously transmit a force 148 a . the force 148 a is the result of unequal loading within the rubber springs 306 . a force 145 acting generally at the pivot 142 is the resultant due to the force 148 a , and the moment 146 acting on the lower link 140 . fig1 illustrates the equal and opposite force 148 b applied to the rubber torsion axle assembly 301 and torque arm 310 , along with the reaction force 312 a as applied to the torque arm . the force 248 a is applied from the mowing unit . the moment 146 is generated by a reaction force 312 a as a function of the relative rotation at the mower pivot 144 , which causes compression of the rubber springs 306 . fig1 illustrates a force 136 a acting at a pivot point 134 , to effectively hold the mowing unit 200 from rotation . the upper link 130 will be subjected to an equal and opposite tensile load , as illustrated in the free body diagram of fig1 . the net effect of the forces applied to the mowing unit 200 is that the ground contact force 250 will be reduced , as a function of the torque 146 . the torque generated within the rubber torsion axle assembly 301 is a function of the relative rotation between the outer tube 308 and the axle 300 . this relative rotation is determined by the position at which the torque arm 310 first contacts the stop pin 206 , and the position at which the mowing unit 200 contacts the ground . the pin 206 can be inserted into one of several holes as illustrated . by changing the location of the stop pin 206 , the orientation at which the torque arm 310 initially contacts the stop pin 206 is modified . this modification affects the relative rotation the axle 300 is subjected to . thus , by adjusting the position of the stop pin 206 , while the mowing unit 200 is in its raised position , as illustrated in fig1 , the amount of torque generated by the axle 300 when the mowing unit 200 is lowered to the operating position , as illustrated in fig5 , is controlled . this adjustment allows the operator to adjust the lift force and thus the resulting ground pressure . the above embodiment is the preferred embodiment , but this invention is not limited thereto . it is , therefore , apparent that many modifications and variations of the present invention are possible in light of the above teachings . it is , therefore , to be understood that within the scope of the appended claims , the invention may be practiced otherwise than as specifically described .