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New S.D. Washes Streets and Fights Fires

22nd December 1950
Page 39
Page 39, 22nd December 1950 — New S.D. Washes Streets and Fights Fires
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AN order recently completed by Shelvoke and Drewry, Ltd., Letchworth, for the Department of Civil Aviation, Australia, was for 10 street-washing vehicles provided with additional equipment to enable the machines to do duty as fire-fighting appliances.

The basis of the outfit is the maker's W-type chassis, which is powered by a four-cylindered 3.62-litre side-valve petrol engine, developing a maximum of 67 b.h.p. at 2,800 r.p.m. A 12-in. single-plate clutch, four-speed gearbox, two-piece propeller shaft and spiralbevel-driven rear axle are other features of a chassis which is notable for its robust construction.

As a street-watering appliance the vehicle is supplied with a tank of either 800-gallon or 1,100-gallon capacity, the dual-purpose outfit having the larger tank fitted. There are two spray heads 3nd three street-washing heads mounted at the front of the vehicle, all being under the control of the driver. ,....

The high-pressure pump, which is of the single-stage centrifugal type driven from a gearbox power take-off, is capable of delivering up to 250 g.p.m. at over 100 lb. per sq. in. pressure with the engine running at its governed speed of 2,400 r.p.rn. A feature of the pump drive from the power take-off is that the gears are in constant mesh, the link-up to the pump being by the engagement of a dog-clutch controlled by a lever arranged for convenient operation from the driver's cab.

A second power take-off drives an exhauster which can also be used to develop a pressure of 10 lb. per sq. in. in the water tank. This exhauster, which, incidentally, is the only chassis unit not made by the chassis builder, develops a depression of up to 27 ins. of mercury and is used for filling the lank from low-level static supplies.

To enable the outfit also to function as a fire-fighting appliance, suitable connections were made for 'hoses, and stop valves, hose lockers and a foam-making unit were introduced. There are two 21-in. hose connections with stop valves, one on each side of the vehicle. Two hoses can be used at the same time, either one on each side, or, by using a divided breeches pipe, two on one side. The machine demonstrated to "The Commercial Motor" was equipped with a Pyrene 40-gallon foam compound tank, a multiple-jet induction head, and two F.B.10 foam-making branch pipes. With 1,000 gallons of water, 8,000 gallons of foam can be produced. Whilst this dual-purpose machine is of generous capacity as a first-aid outfit, it can also be used on continuous service, provided that there be available an external static water supply or a hydrant.

Augmented Engine Cooling

When the appliance is arranged for continuous running it is necessary to augment the normal cooling arrangements for the engine, and this is provided for by arranging a direct water -feed to the normal cooling system of the unit.

All the controls governing the streetwashing and spraying heads are in the cab and clearly marked, whilst those used when fire-fighting are located at the forward end of the water tank on the left-hand side, where the 40-gallon foam tank is also located.

Through the medium of the controls it is possible to fight a fire with water or foam, as desired. A feature of the S.D. outfit is its large capacity as a firstaid fire-fighter, for it is considered that with full tanks of water and foam it is possible to deal with four burning aircraft.

There is ample locker space provided on each side of the main water tank: in this instance the lockers are used to carry about 50 ft. of suction hose and 300 ft. of 2i-in, delivery hose. These lockers can be adapted in any way to meet, the purchaser's requirements.

The demonstration staged for "The. Commercial Motor" covered street cleansing and fire-fighting, and on both duties the machine performed in an exemplary manner,


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