Novel Mechanical Features in
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New American Mack Range
"Power Divider," ,in Double-drive Six wheeler, with Bias of Torque to Wheel With Best Traction
A NUMBER of interesting features is included in the several chassis comprising a new range of models recently announced by Mack Trucks Inc., Long Island City, N.Y., U.S.A. It consists of two four-wheeled lorry chassis, three tractors and three six-wheelers, expressly designed and built for heavy duty.
Each type is offered with a choice of petrol and oil engines, ranging in output from 118 b.h.p. to 160 b.h.p. The lorry chassis are also available in a wide variety of wheelbase lengths, whilst the tractors can be supplied in standard form or with a special wheelbase dimension for sleeper cabs.
There are six sizes of petrol engine listed, all bearing the name Mack Thermodyne, whilst the choice of. compressionignition units, designated Mack-Lanova, is limited to two— of 131 b.h.p. and 144 b.h.p. respectively.
Amorig outstanding features of the petrol engines in the Mack-Thermodyne range is the standardization of the Lanchester crankshaft vibration damper. All the Mack. chassis have five-speed gearboxes with either direct or 'overdrive top gear. Alternatively, the Mack Duplex 10-speed transmission is available.
On the tractor models double-reduction final-drive units are employed, no fewer than five ratios being offered. The six-wheelers have four-wheel drive of a design that ensures equal distribution among the four tyres of supported load, braking force and tractive effort. In the suspension system rubber shock insulation is used, whilst the layout permits a wide spring base.
Included in the bogie mechanism is the Mack power divider, Which produces constant torque without end thrust. It does not depend upon friction, for its functioning nor is it a ratchets or inertia device. The maker claims that it operates indefinitely without developing backlash or losing its partial locking action. Although named a power divider, it provides, we understand, a bias of torque to the wheel having the best traction, but the power transmitted can, in no circumstances, exceed a safe limit because full differential action comes into play so soon as the predetermined bias maximum is exceeded.
Common to the tractor and six-wheeled models are airoperated brakes, whilst the four-wheelers have vacuumservo hydraulic retardation apparatus. Differing from the older models, which have high-carbon heat-treated-steel frames, the new four-wheeled model and the latest sixwheeler have chrome-manganese steel frames. All employ the company's special design of box-section cross-member, an example of which js clearly shown in the accompanying picture.