source to open the pilot operated check valve 90 and establish communication between the annular chamber 80 through the pilot operated check valve 90 and the control valve 94 to the tank 98 preferably the source 96 provides hydraulic fluid at a pressure of about 1000 psig with a flow rate of about 5 gallons per minute by using the comparatively low hydraulic pressure the cost of hydraulic equipment is minimized since higher pressures require more sophisticated seals and manufacturing tolerances the flow rate of 5 gallons per minute provides an acceptable response time for amplitude adjustments an alternate embodiment of the present invention is particularly well suited for rollers in which the roll is comparatively wide a wide roll is illustrated in fig3 with elements corresponding to elements of fig2 having the same reference numeral applied thereto and differentiated by the addition of a superscript 39 the following description relates only to the differences between the embodiment of fig3 and the embodiment of fig2 it is understood that the description herein relating to elements of fig2 is equally applicable to the corresponding elements of fig3 the shaft 28 39 see fig3 includes two cylinders 38 39 138 each having a corresponding axis 41 39 141 disposed transversely of the shaft axis 24 39 and preferably perpendicular thereto the axes 41 39 141 are axially spaced apart along the shaft axis 24 39 and may be equally spaced from the corresponding adjacent shaft bearing 30 39 32 39 this location.