by linear movement of the cam relative to the shaft along a slot elongated about a radial line interconnecting the geometric center of the cam with the locus of the rotational axes to change the stroke of the needles without changing the timing of the needles relatively to the loopers a pair of locating plates fastened to the shaft have hubs received within the slot at preselected positions the cam and plates having indexing holes that can be selectively aligned for the desired needle stroke another drive similar to the needle drive but 180 degrees out of phase therewith reciprocates a weighted carriage to counter balance the rotating and reciprocating forces of the needle drive system a threaded adjusting rod is threadedly received within hollow push rods for adjusting the needle bar to maintain the bottom dead center position of the needles at a predetermined position regardless of the selected stroke a two member backing bar provides rigidity to the needle bar the members being adjustable with respect to each other to provide a fine adjustment to the location of the bottom dead center of the needles application_number US 54036583 A description referring now to the drawings there is illustrated a.