Differential for All-wheel-drive Six-wheelers
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CONS1DERABLE interest attaches to a differential gear designed by Mr.. H. B. Dodge, chief engineer of the Four Wheel Drive Auto Co., of Clintonville, Wisconsin, U.S.A. It is expressly built for use in connection with the conaparets latest types df six-wheel-drive lorry and is described as a power-proportioning differential which distributes the driving torque to the front and rear axles respectively, in direct proportion to their tractive capacities, whilst providing full differential action.
'Although complete technical details of the new gear have not so far been made public, it is stated that in the new lorries, which have twin tyres on the four wheels of the rear bogie axles, the gross weight is so arranged that 20 per cent, of the load is carried on the two tyres of the front axle and 80 per cent, on the eight rear tyres,' the driving torque being delivered to the respective axles in that ratio.
Referring to the accompanying illustration, of the improved gear, we observe that the side bevel wheels have unequal radii, the differential pinions being arranged to correspond therewith. The ratio between the pinion and side gears is such that the mechanism operates as a continuous lever and the same force applied on the shorter leverage of the differential side gear connected to the front axle reduces the torque applied to that axle, whilst the same force applied to the rear leverage of the larger side gear connected to the rear bogie increases the torque to the bogie's two driving axles.
In other words, the differential bevels on the star-piece are in a state of balance when the load on the front-wheel shaft is one quarter of that on the bogie shaft.Thus there is normally no" relative movement between _any of the gears except when differential action occurs as a result of the truck rounding a corner, or travelling over rough or uneven ground, or in the event of wheelspin.
It would appear" that the device represents the simplest and most compact means for distributing unequal torque that is practicable, furthermore wear and maintenance are reduced to a minimum.