10 the spherical bearing members not only serve to maintain the pistons 34 against rotation in the cylinders 20 but also to take up the side thrust developed upon the pistons 34 by the inclined surfaces of the cam ramp 56 and the rollers 40 still further the spherical bearing members also sere to take up most centrifugal forces acting upon the pistons 34 during rotation of the skeletal cylinder assembly 14 thus the spherical bearing members 116 serve three different purposes the opposite end cavities 118 of the casing 12 have oil spray and mist therein as a result of oil being ducted through the piping 46 and the journal sleeves 38 and thus the bearing race blocks 104 and 112 as well as the spherical bearing members 116 are adequately lubricated in addition the o ring seals at 26 are lubricated in the same manner while the o ring seals 32 receive low pressure lubrication through oil lines 120 see fig2 in order to cool the cylinders 20 the casing 12 includes a double row of circumferentially spaced water spray heads 122 disposed thereabout for sprayed discharging cooling water onto the longitudinal midportions of the cylinders 20 between the partitions 28 the central cavity 124 of the interior of the casing 12 disposed between the partitions 28 may have a suitable drain not shown for.