in the drive assembly of a reciprocating slat conveyor , three transverse drive beams extend over and across three piston rods . the drive beams have side flanges in which three pairs of downwardly opening recesses are formed . one pair of recesses receive upper portions of a first piston rod . the other two pairs of recesses receive plastic bearings through which the other two piston rods extend . each drive beam flange is provided with a cap member . each cap member includes an upwardly directed recess for each downwardly directed recess in its drive beam flange . bolts extend through openings in the cap members and thread into internally threaded openings in the drive beam flanges . each piston rod is provided with a member which provides radially upwardly projecting pairs of flanges between which the drive beam flanges are situated . this provides an interlock structure that connects the piston rods to the drive beams so that piston rod motion is transmitted to the drive beams . as each drive beam moves front to rear along with its piston rod , it slides relatively along the other two piston rods that are situated in bearings that are carried by the moving drive beam . the engagement of the drive beams with the piston rods via the bearings results in each drive beam being braced from the other two piston rods against yaw , pitch and roll movement .