Abstract: A rack and pinion gear and a method of assembling such a gear. The gear has a rack bar 1 the rack 4 of which is biased into engagement with the pinion 6 by a spring loaded support 7 which slidably (or rolling) engages a bearing surface 8 of the rack bar. The bearing surface has a central region 9 parallel to the rack axis and tapering end regions 10 and 11 which reduce the thickness of the rack bar from the central region 9. The length C of the region 9 corresponds to 1 to 1.5 revolutions of the pinion 6 while the operative length A of the rack corresponds to at least three revolutions of the pinion. The pinion rotates about an eccentric axis 14 which varies the rack bar tightness. To determine the position of maximum tightness in which the spring loading of the support 7 is to be adjusted, the pinion is rotated from a central position on the rack 4 clockwise and counter-clockwise to displace the rack bar in each instance through a distance corresponding to 0.

Abstract: A variable ratio rack and pinion gear having a rack bar (1) the rack (8) of which engages with the pinion (10) so that rotation of the pinion displaces the rack member (1) longitudinally relative to the housing (6). A yoke (25) supports the member (1) with its teeth in engagement with the pinion and straddles the member (1) to restrain displacement of that member relative to the housing (6) in a direction parallel to the axis of rotation for the pinion (10). The rack member is restrained from rotation relative to the housing, and (1) has a longitudinally extending non-rectilinear grooved track of one or more curved portions (14) which is engaged by a peg (17) rotatably carried in a mounting block (21). The block (21) retains the yoke (25) in the housing with the peg (17) located within and extending through the yoke (25).