ENGLISH MOTOR FIRE ENGINES
The turbine petrol motor fire engines shown in the accompanying illustration are in operation at Birkenhead and Kingston, England, and the machine farthest away was built for the Christchurch fire brigade hoard at Christchurch, New Zealand. These turbine fire engines are of the Dennis type, constructed at Guildford, England, and all are fitted with 6-cylinder engines of 75horsepower, and have a capacity of 450 gallons of water per minute at 140 to 150 pounds pressure. They can also deliver up to 800 gallons per minute at lower pressures and readily attain a sped of 45 miles per hour on the road. The engines are provided with block section tires, as shown in the illustration, which enables the machines to cross soft ground with ease and also act as a preventative to skidding. The accompany drawings show the construction of the DennisCwynnc turbine motor lire chassis and the system of wiring with a Bosch magneto as well as with accumulator high-tension electric wiring. The details of construction of the worm drive rear axle, the construction of the pump and arrangement of hydraulic connections, suction inlet, outlet valves and bypass to tank, as well as charging tank are shown in the sectional drawings.
It may he stated that the pump is of the multistage turbine or centrifugal type, with automatic charging apparatus, comprising a tank, with a capacity of 50 gallons of water, if required, 40 gallons of which can be utilized for first aid purposes, the necessary pressure being generated by running the pump and leading the small hose from the pump outlet by using an adapter. The 10 gallons remaining after this is used is quite sufficient to start the pump and it is automatically retained for this purpose. A bypass is taken from the pump outlet conveying the water along the chassis through a strainer, and then through a cooling coil of pipe in the oil tank to lower the temperature of the oil, which increases its lubricating properties, and from there into the radiator, to which is fitted a large overflow pipe, so that there is a constant stream of cold water to assist the cooling of the engine when pumping. A special charging apparatus is applied when the suction pipe is used in working the motor fire engine with water supplied from a dam, river or canal. The object of this appliance is to draw the water up the suction pipe to enable the pump to take it on and start delivering. The ejector principle is used and the method of operation is unique. A tank of water is connected to the inlet of the pump by a pipe (F); the outlets of the pump are closed, and a separate bypass conveys the water back to the tank, passing through the ejector i (B), thus there is a complete circuit from tank to pump and from pump hack to tank. There is a valve shutting off the ordinary suction inlet so that the water entering the pump through the pipe (F) cannot run away down the suction, also that the ordinary delivery outlets are closed. As the pump is running, the water will be delivered to the ejector (B) under pressure, and passing through a cone nozzle, it causes a vacuum in a chamber immediately round it. This chamber is connected to the suction pipe below the non-return valve by means of the vacuum pipe (D), which quickly exhausts the air from the suction As soon as the water has reached the top of the suction, which can be seen by looking at tin water gauge, the ejector is shut off, and the ordinary outlets (K) opened. The same water in the tank is used as often as required, as it will be seen this is only circulated and is not used for flooding the suction or other usual method of charging centrifugal pumps. When necessary to refill the tank while the pump is working, it may be done by opening the valve (E). This English motor fire engine is unique in construction and said to be highly efficient in its operation.