Double-drive Mastiff for new top weight
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• A Leyland Mastiff-based double-drive six-wheeler plated at 24 tons gvw — the proposed new maximum weight on three-axled rigid chassis — has been introduced by Unipower Ltd, Perivale, Middx. The third axle conversion carries full British Leyland approval.
An Eaton 38DT bogie is employed, its 1900 series axles each being plated at 9 tons. Unipower's earlier Mastiff sixwheelers, rated at 22 tons gross, have been fitted with the lighter 1800 series Eaton driving axles.
Bogie suspension is to full 18 tons capacity. The four interchangeable seven-leaf springs are 47in.-long and 3.5in.-wide, linked front-to-rear by a centre bracket and rocker beam assembly.
Additional reinforcement of the main longitudinals to cope with the 2-ton increase in gross weight takes the form of a greater overlap in internal and external flitching of the channels. The 0.25 in. thick L-shaped flitch outside the web and bottom flange now extends back to the first pair of bogie spring hanger brackets, while the inverted-L internal flitch above the span of the bogie suspension is now carried forward to th crossmember supporting the centr prop-shaft joint.
A further 3in. by 0.38in. reinforcing stri is welded along the top of the chassis t increase the compression strength of the tc flange.
With an other axle spacing of 18ft lin the 6 by 4 Unipower-Mastiff qua& comfortably for 24-ton operation under th latest DoE proposals. The 4ft 4in. bogi wheelbase meets the new requirements o equalizer tandem suspension for an impose loading of 18 tons.
Unipower uses as the basis for th conversion a lift 3in. Mastiff 16-to two-axle chassis, so that no frame extensia is required. The existing Eaton two-spec driving axle is retained as the second axle c the bogie, a through-drive Eaton assembl with built in third-axle differential lac being added. Standard ratios are 6.14 an 8.54 to 1.
Westinghouse spring brake actuators as provided on the third axle so that all thre axles are braked for parking as well 2 secondary operation.
Unladen chassis-cab kerb weight of th new machine is 6 tons 6cwt. The retail pric of the conversion is £1685 plus a fittin charge of £225 net.