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Aviation History
1943
1943 - 0311.PDF
FEBRUARY 4TH, 1943 FLIGHT 123 HYWRAUUt MQ10R ft«O SEBtfOltm GEAR Fig. 1—A typical B.P. power control system. The control handle incorporates a "dead man's handle which, whendepressed, energises the electric motor. pipes and fluid, and leakages and fractures caused by vibration. This latter benefit results from the short pipe lengths and the ability to bend them to conform with neighbouring structure to which they can be ade- quately cleated. The whole of the power units are built into the turret, leads for electric power and other services being taken to a slip ring unit on the axis of rotation, so that installation consists only of dropping the turret into position, lining up, bolting down and coupling up electrical services, and. in some cases, an external oxygen supply. The advan- tages of this method will be readily appreciated. All ground tests and adjustments can be made before installation in the aircraft, and the minimum time is taken in removing and replacing a damaged turret. Operationally, an outstanding advantage is that power is only used as and when required, and there is no appre- ciable difference in speeds of operation either up or down wind. A brief description of turret operation will help to make these points clear. The control handle incorporates a grip lever or "dead man's handle" which, when depressed, energises the electric motor, and since this opera- tion is naturally only performed when the gunner desires to put his turret into operation, no power is consumed when the turret is idle. A typical power control system is shown in Fig. 1. Overloading Prevented The hydraulic generator incorporates relief valves, set to a blow-off pressure which, at full output from the generator, limits its power to that obtainable from the electric motor. There is, therefore, no danger of either the electric motor or the hydraulic generator being over- loaded. Movement of the control handle imparts stroke to the generator pistons, the power output being proportional to (a) the stroke imparted, which governs the speed of turretmovement; and (b) the pressure built up in the hydraulic system (up tomaximum blow-off pressure) determined by the external resistance to turret movement. It will be observed that for any turret speed the power output from the hydraulic generator, and consequently power input into the electric motor, is a function of turret speed and of the pressure required to overcome external resistance to turret movement at any instant—limited, ot course, to the maximum determined by the setting of the blow-off valves—and the speed of the turret is virtually independent of turret movement upwind or downwind. The foregoing outlines the general principles of the Boul- ton Paul system of turret operation and its main advan- tages, and while it is not proposed to give a fully detailed description of the whole range of turrets develcped by the company, there are features associated with the various types which may be of interest. From the diagram, Fig. 2, it will be seen that the hydraulic pumping unit (known as the generator) com- BLEEDERVALVE GUN ELEVATIONRAM Fig. 2.—A hydraulic system representative of Boulton Paul practice. The hydraulic generator unit comprises two separate pumps, one for turret rotation and the other for elevation of the guns.
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