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DENNIS DEVELOPMENTS
A New Type of Fire Pump with its Turbine Centrally Mounted. An Interesting New Testing Plant for Fire engines. The Performance of the Latest Dennis Dart 20-seater Bus
URING a recent call at the worka L.1 of Dennis Brothers, Ltd., Guildford, we were able to note several developments of importance. The first is an amendment to the well-known Dennis low-loading fire pump ; this consists of the mounting of the 650-800gallon turbine immediately lielow the driving seat. The advantages of this system are that, when an escape ladder is carried at the rear, this need not be disturbed on arrival at the fire in order to gain access to the pump. There are many occasions on which the escape is not required and it is only wasting time if this has to be dismounted before the firemen can couple hoses to the pump and get to work.
Another good feature which results from this disposition of the pump is that a slightly greater weight is thrown upon the front wheels, as normally the whole of the pump, when mounted at the rear, is an overhanging weight which must make control of the chassis at high speeds rather more difficult.
If it be found necessary to use the escape after pumping has commenced, B24 these engines was being completed for
the West Ham Fire Brigade. It is equipped with the 90-100-b.h.p. sixcylindered Dennis engine of the sidevalve variety, having dual ignition and being capable of propelling the camplete outfit at about 40 m.p.h.; it will tackle gradients of 1 in 6 with a full load. In order to cope with the high speeds which are essential in firebrigade work the four-wheel brakes are operated by a vacuum servo.
The Dennis multi-stage turbine pump is of a pattern which has giveh long and satisfactory service. It has a suction inlet on each side of the chassis and two delivery outlets on 'each side. The output is 650 gallons per minute at 120 lb. pressure per sq., in. and up to 800 gallons per minute at lower pres sures. The machine can still be supplied with the_ pump at the rear, it preferred.
An interesting new feature at the works is a testing tank for fire-engines. The vehicle is driven on to the concrete beside the tank, the suction hose lowered into the water and the delivery hoses coupled to fixed nozzles which discharge into a concrete butt, the water returning to the tank. There is a shed adjacent for the ,use of the testing staff.
By means of this installation the
Dennis concern is able to avoid any need for taking a fire-engine to a river. or stream for test purposes, thus obviating possible inconvenience to others and saving the need for expense in road trials or the risk a becoming ditched on inferior surfaces which frequently exist beside watercourses.
On the occasion of our visit we travelled on a Dart 20-seater bus over a 36-mile test course. It was laden to represent a full load and, when travelling on main-road work, gave a fuel return of 15 m.p.g.—a creditable figure
for a machine of this capacity. On
work corresponding to urban service in billy districts the result obtained was III m.p.g. In the first ease the average speed was 264 m.p.h. and in the latter over 29 m.p.h., despite all the atops, so that it will be.. realized that the Dart engine is capable of giving a high performance at a small fuel cast.
• The bus ran silently and attained 52 M.p.h, with a high service-type body,
giving the full headroom. It proved itself capable of restarting with ease on a gradient of .1 in 6, and accelerating. on a level road, from 'rest to 40 m.p.h. in 39 seconds, so that its good fuel consumption is not achieved at the cost of inferior flexibility.
The climb up to the Hogs Back was accomplished at an average speed of 23.4 m.p.h., the distance being 1,8 mile, commencing from the hair-pin bend by Guildford station and finishing at the R.A.C. patrol box. The hair-pin was rounded on second gear, and during the climb it was possible to use top gear over two stretches, thus demonstrating its pulling powers on direct drive.
The brakes were smooth in operation and powerful, and each system was able easily to hold the laden vehicle on a 1-in-6 gradient ; the pedal operatea four-wheel brakes through
Dewandre servo. The siX.cylindered engine showed no trace of vibration at any point in the speed range, and the general standard of silence was high. There is no fuss when
cruising at 50 . The rear-axle ratio is 6.2 to 1 and is well suited to the engine's capabilities.
Readers will .recollect that several of these. popular Medium-capacity buses have recently been supplied to the London General Omnibus Co., Ltd.