CHANGES TO A.E.C. MARSHAL 6 x 4
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FOLLOWING our March 13 announce" ment that a four-spring bogie had been adopted as standard for the A.E.C. Marshal 20-ton-gross 6 x 2, A.E.C. Ltd. this week give details of a similar change to the 6 x 4 model. As originally introduced, the Marshal 6 x 4 had an EatonHendrickson bogie layout utilizing walking beams and rubber "load cushions but for the past year or so chassis were being built with the steel-sprung version of this bogie. Now the Hendrickson type of bogie has been dropped altogether in favour of an all-A.E.C. four-spring layout.
Suspension layout of the double-drive bogie is identical to that of the singledrive model described last month. As beiore, the driving axles are singlereduction spiral-bevel assemblies, but whereas the original vehicles had basically Eaton axles (incorporating A.E.C. hubs and so forth) with a reduction ratio of 7-17 to 1, the new model has A.E.C. axles, available with ratios of 7.14 or 7.85 to 1. An air-operated lockable third differential is incorporated. The chassis frame of the new design is heavier than that of the 6 x 2s and of the original 6 x 4s, having been adopted when the change was made to the steelsprung version of the Hendrickson bogie. The side members have a thickness of 0-3125 in., with a maximum depth of 12.0 in. and 3.3125-in. flanges, whilst the original frame had a thickness of 0.2813 in., a maximum depth of 101875 in., and 3.0-in. flanges.
The new design has Girling camactuated brakes at all axles, with full air pressure operation, the total lining area being 1,100 sq. in. Earlier versions of the Marshal 6 x 4 had Girling wedgeactuated two-leading-shoe brakes on the rear axles, with air-hydraulic operation, although the total lining area of these vehicles was the same as on the new ones. The air-pressure servo for the handbrake linkage detailed in our description of the Marshal 6 x 2 is available on the new 6 x 4 also; as is power-assisted steering.
The A.E.C. AV470 diesel rated to give 138 b.h.p. at 2,200 r.p.m., is standard in the 6 x 4, driving through a D197 fivespeed gearbox, which is available with a sixth overdrive ratio. The specified wheelbases are as before-11 ft. 9 in., 15 ft. 7 in. and 17 ft. 5 in.—and although officially limited to, 20 tons gross in Britain, the chassis has been designed for a gross Weight of 22 tons in anticipation of increases in the British legal maximum weights. Quoted kerb weights for the three chassis mentioned above are 5 tons 9.5 cwt., 5 tons 13.5 cwt. and 5 tons 14.5 cwt. respectively.