More Powerful Version of Nubian
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TO meet the need for an airfield crash and a water foam tender with a capacity and a performance as required on today's larger airfields and runways, a more powerful version of the Thornycroft Nubian has been introduced, Called the Thornycroft Nubian Major it is a three-axle vehicle with six-wheel drive and designed for a gross weight of 20 tons.
One of the most interesting aspects of the design is that a Cummins V8-300, eight-cylinder diesel engine with a maximum output of 300 b.h.p. gross at 3,000 r.p.m. and a maximum gross torque of 580 lb.ft at 2,100 r.p.m. is used. The capacity of this engine is 785 cu. in (12-86 litres), bore and stroke dimensions being 5-5 in and 4125 in respectively. The engine drives through an 18-in.-diameter combined hydraulic coupling and centrifugal plate clutch to a fivespeed epicyclic gearbox with direct air operation, which is unit mounted with the engine. Ratios of the gearbox arc 7.25, 4-28, 2.43, and 1-59 and 1 to I with reverse 5.97, and the drive is taken from this unit 14 a short propeller shaft to a two-speed, constant-mesh auxiliary box which, as well as dividing the drive between the front axle and rear bogie. also provides a step-down ratio of 1-64 to 1. Whilst this theoretically gives a 10-speed transmission, the only ffective step-down ratios are bottom and reverse, a combination of auxiliary low and the other ratios resulting in overall figures similar to the ratios already existing in the main box.
All three axles have double-reduction drive through ipiral-bevel and double-helical gearing. The ratio at the front axle is 7-84 to I and of the two rear axles 7-89 to I. Font wbeel drive engagement in the auxiliary gearbox is operated by air-pressure. Braking is, by a dual-circuit airpressure system, the brake units being 17 in. diameter by 4-25 in. wide at the front axle and 15.5 in. by 7 in. wide at the rear axle. Total frictional area is 1,084 sq. in. The handbrake operates directly to the rear bogie and cam and double-roller steering with hydraulic power assistance is fitted.
Two-spring rear bogie
Suspension is by semi-elliptic leaf springs with telescopic Jampers at the front axle and at the rear the A.E.C. fullyarticulated two-spring bogie. is used. The frame is of bolted construction. the channel-section side-members haying a maximum section of 10 in. deep by 3 in. flanges and ;1K-in.-thick material. The tyre equipment is 14-00-20, 21-ply, With single wheels all round, and optionally .15-00-20, 1.0-ply.
Electrical equipment includes a 7-in, alternator with an output of 1,440 w. The electrical system is 24 V. insulated return and the batteries are 165 amp. hr. capacity.
Optional equipment available for the Nubian Major includes a top-mounted main gearbox power take-off with synchromesh engagement which can be engaged while the vehicle is on the move, thus permitting foam discharge when travelling. This power take-off can deliver full engine power for periods up to 30 minutes, An auxiliary gearbox power take-oil and a heater exchanger in the engine cooling system to utilize by-pass water from the fire-fighting pump are also available.