Three New Proprietary Components The David Brown 1936 Programme Includes Redesigned Steering Units, Clutches and Four-speed
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"Silent" Gearboxes
CLAMING to be "the world's largest gear maker," David Brown and Sons (Hudd.) Ltd., Huddersfield, is introducing at the forthcoming Show three chassis components of absolutely new design. They comprise a steering box, incorporating the latest developments in worm gearing, and made in a number of sizes for commercial vehicles of different capacities; two models of a single-plate clutch for 9-tonners and 12-tonners (gross laden weight); and a gearbox, available in types suitable for vehicles in the same two categories, and with constant-mesh ground helicaltoothed third and second-speed gears.
Of the steering box, the leading feature is the patent design of the worm thread, which its maker describes as of the " arc-contact " type. Briefly, it affords a high degree of efficiency when the worm is driving the sector, thus giving light and sensitive action, whilst when the drive is reversed the efficiency is low and, in consequence, shocks are absorbed. • The mechanism is housed in a one piece casing, of aluminium or malleable iron, which incorporates the mounting bracket. This construction results in great rigidity. The worm forms a unit with its shaft and is bored, if necessary, for control shafts.
Characteristics that have been embodied in the new clutch include the ability to function under heavy loading without excessive heat generation, lightness, robustness, duraflinty and simplicity of maintenance. The withdrawal gear is of new design and simple construction, permitting no wedging nor chatter when picking up the drive. Provision has been made for the successful functioning of these clutches under the high torque generated by oil engines, the two models being suitable for torques of 250 lb.-ft. and 333 lb.-ft. respectively.
The same modern requirement has influenced the design of the new range of gearboxes, but it is net only the efficient transmission of high torque that has been studied, for attention has also been paid to silent running, mounting problems, adequate lubrication, light weight, compactness, and ease of changing from ratio to ratio.
As mentioned earlier, the " third " and " second " wheels are in constant mesh, being engaged by sliding dog clutches—as is the direct drive—and it is of interest that these gears run on needle-roller bearings. The first-speed wheel is the only sliding gear. It has internally generated involute teeth and moves axially on a sleeve with similarly formed splines.
Lubrication of the wheels is by splash, but a screw-type oil-pump feeds the spigot and needle-roller bearings, via the hollow shafts.