New Aircraft Towing Tractor C APABLE of towing aircraft weighing over
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100,000 lb., the new Tugmaster Series 4 tractor, produced by Douglas Equipment, Ltd., Tewkesbury Road, Cheltenham, has been proved under test to produce a tractive effort of 8.700 lb. on wet concrete. Its small dimensions and turning circle of under 9 ft. radius provide many advantages for manceuvring in confined spaces.
The overall height, measured from the ground to the bonnet, is 3 ft. 94 in., whilst the height of the driver's head is approximately 4 ft. 8 in. The wheelbase 4 ft. 10 in., length 10 ft. 3.t in., and width 5 ft 2+ in. Minimum ground clearance is about 7 in.
Good traction is provided partly by employing the maximum size of tyre for the driving wheels compatible with low height, the tyres being Dunlop Trakgrip 10.00 in. by 20 in. 14 ply. The front wheels are equipped with 7-in. by 9-in. 10-ply tyres of the same make.
The tractor is also available as an industrial unit which may be fitted with modified frame and 10.00-in. by 20-in. tyres at the front and rear to provide a ground clearance up to 10 in. This type is particularly suited for use in factories and goods yards. Auxiliary equipment can be provided to meet individual requirements.
A Perkins P6 oil engine with a rated output of 83 b.h.p. at 2,450 r.p.m. gives a torque of 202 lb.-ft. at 1,400 r.p.m., which is transmitted through a VulcanSinclair fluid coupling to a Borg and
.Beck 12-in, dry-plate ventilated clutch and thence to a four-speed gearbox with baulk-type synchromesh applied to top, third and second gears. An auxiliary gearbox, with a ratio of 1.41 to 1, is mounted behind the rear axle.
The final drive is a Douglas Spiral-bevel reduction gear with a ratio of 7.14 to 1, and the axle is of the fully floating type. Braking is applied to the rear wheels, a total facing area of 407 sq. in. being provided. The Girling two-leading-shoe brakes are hydraulically operated and assisted by a vacuum servo.
Ease of starting under the most severe conditions is afforded by a Berger pneumo-hydraulic starter at a pressure of 4,000 p.s.i.
The starter is flame proof and a flame trap is fitted to the exhaust. The engine cooling system is pressurized to 5 p.s.i. and designed to maintain a normal working temperature up to an ambient temperature of 110° F.
A larger model of the Tugmaster, the Series 5, powered by a similar unit or a Perkins R6 engine, will be capable of a tractive effort of 19,000 lb. with singleaxle drive and of 22,000 lb. with fourwheel drive.