a detent flange 408 which acts in cooperation with bearing block 410 and retaining collar 412 block 410 is secured to frame 108 via mounting bracket 311 which is in turn connected via angle bracket 422 to stiffening plate 426 best seen in fig7 the threaded end 430 of shaft 406 is threadably engaged with adjusting post 432 and terminates in a pinned threaded collar 434 adjusting post 432 is mounted within yoke block 436 one end of lever 438 is connected to yoke block 436 while the other end is provided with an aperture 440 for mateable engagement with shaft 442 having axis 443 as seen in fig1 and 5 adjusting post 432 is connected to a shaft 435 the upper end of which is rotatably retained within aperture 444 of mounting plate 446 by a pinned retaining collar 448 the function of plate 446 will be explained below with reference to fig8 the other end of shaft 442 is fixedly secured to bell crank and bearing support 450 which is welded to bracket 319 the other end of bracket 319 serves to pivotably secure pivot block 250 best seen in fig1 and 5 in operation as control handle 400 is rotated shaft end 430 will rotate within adjusting post 432 causing it to move longitudinally along the shaft post 432 is free to rotate within yoke 436 and rotation of the shaft 430 causes yoke 436 and lever 438 to pivot about axis 443 this in turn causes pivot block.