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Aviation History
1943
1943 - 0315.PDF
FEBRUARY 4TH, 1943 FLIGHT 125 POWER-OPERATED GUN TURRETS St'itOCKUS SECURED "u UNfitRStDE OF s ""pest TiBlf .> I Jni '-.A :0H ANtl \ ,'>HilE tABtt St,io»l4b BftU^H CAB1I IMD* 111 HRIHI. ii«ujirs fUrtH SPRING 'MlDIHG BRUSH RUBBER ELBOW Fig 5-—D;agram of a typical gun-fire interrupter mechanismFiring of left-hand and right-hand guns or pairs of guns is interrupted individually. A supply of oil is carried in a sump in the generator for making up internal leakages as needed through suction valves in each circuit. Overload protection is given by blow-off valves in each line, these valves being set at pressures of approximately 1,000 lb. per square inch. The hydraulic generator, which runs at 1,230 r.p.m., is driven by a constant-speed 24 volt electric motor running at 4,000 r.p.m., coupled through epicyclic gearing to the generator to form a single unit. It will be understood that the two pumps are controlled independently and both azimuth and vertical traverse can take place individually or simultaneously. The design of the hydraulic system incorporates small electric resistance heaters of approximately 50 watts load- ing—automatically cut out when the turret is in operation —in the hydraulic generator and motor. These heaters assist when functioning at low temperatures. The Hydraulic Motor The hydraulic motor (see Fig. 4) is of the seven-cylinder elliptical,cam type, of fin. bore and 0.45m. stroke, with the cylinder block as the driven member rotating on a stationary distributor spindle. Power strokes occur in opposite 90-deg. sectors, and the motor is reversed by reversing the supply of hydraulic fluid from the generator, determined by the position of the control handle. The materials of construction are similar to those used for the hydraulic generator, with delivery and exhaust ports formed in the distributor spindle., provision being made for adjust- ment of port timing by partial rotation of this spindle. The approximate maximum speed of the hydraulic motor is 200 rp.m., and connection is made to the internally cut main driving gear through epicyclic gearing. Gun and seat rams, where the latter are iitted, follow normal practice, the only point for comment being the con- struction of the piston, in which all screw joints for retaining the synthetic rubber cup washers aie eliminated, the washers being retained by a " dead " spring ring and "D washer, avoiding any tendency to squeezing out or damage to the cup washers. (See Fig. 2.) ' The pressure regulator or metering valve interposed in the pipe run to gun rams serves to maintain a small back pressure on the return line, and this unit also provides a means for short-circuiting the gun ram when it is required to man-handle guns without power. Reference to Fig. 2 will clearly indicate the operation ot the hydraulic circuit, and it should be .noted that the system is virtually closed, i.e., return fluid from hydraulic motor and rams is fed back to the inlet side of the hydraulic gen- erator, and not into the pump. The make up valves func- tion only under normal operation to permit replacement of fluid lost through interport and piston leakage, and to feed the intake side of the hydraulic generator when blow-off valves are operating. Gun-fire Interrupter Each gun is electrically fired by a separate solenoid, a single firing button controlling all guns being mounted in ths top of the control column. A safety isolating switch is included in the circuit. One of the first problems which had to be solved was protection for surrounding aircraft structures, such as tail, airscrews, etc., from rounds fired from the turret, without calling for any conscious effort on the part of the gunner, as it was realised that with guns spaced fairly widely apart, and not in the line of the sight, the gunner would be look ing past parts of the aircraft at which his guns might actually be pointing To overcome this difficulty an elec- trical fire interrupter device is fitted in the firing circuit. THE TWO BELTS A«£ SEP4RAUD BY » CEHT8E WEB IN THE DIKT \ LINK OtUU AMMUNITION CHID ROLUR tMPTI CHRtKIOGE CASt lONTAtNHt - .-»*, EJECTION Of LINKi AHD CftSES 1HR0UGH HOU.0W GUN PLATE SUPPORT TO EMPtV CARTRIDGE CME COHIUNER \ . AMMUNITION BOXES Fig. 6—A typical ammunition system as employed in mostBoulton Pau1 power-operated gun turrets. This is of tairly normal arrangement and should be compared with the specialtail turret arrangement shown on the next page.
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