Abstract: Disclosed are reciprocating carriage arms carried on roll bearings engaged on guide rails, where the arms are independently driven, having common "shared" magnet means. The coil-mounting portion of each arm is "twisted" 90.degree. so the set of coil units align along a common "magnet-plane" spanned by common drive magnet means. Also, the arms each mount three load-beams (heads) in "staggered" array to thus shorten the arm-stroke. Opposing sets of the guide rails are provided each on a unitary guide plate with the plates being coupled capturing the respective roll bearings therebetween for a unitary guide box means for all the carriage arms.