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Aviation History
1957
1957 - 0070.PDF
FLIGHT, IS January 1957 BRISTOL 192 . : . 1 Collective-pitch control stick. 2 Cyclic-pitch control stick. 3 Yaw-control pedals. 4 Hand trim-wheel. 5 Hand throttle-levers. 6 Cyclic-pitch cross-shaft. 7 Eccentric torque-shaft (collec- tive and mixing). 8 Collective-pitch cross-shaft. 9 Azimuth and yaw lever assembly. 10 Cyclic-pitch inertia dampers. 11 Yaw inertia dampers. 12 Yaw-contro! sprockets (to yaw- control cross shaft levers). 13 Yowconurol cross-shaft. 14 Eccentric levers (engine con- trols). 15-17 Engine control rods. 15 Engine control levers. 19 Articulating joint. 20 Collective-pitch sleeves. 21 Reversing levers. 22 Inertia damper. Control system of the Bristol 192. The engine-control eccentric-/#v#r detail (item 14) is typical of many of the control assemblies. Below, rotor-hub assembly, showing control spider, blade levers, drag- hinge and inter-blade dampers, anti-cone and droop stop rods and blade sleeves. Leonides Major with the minimum of structural alteration.Transmission. Three gearboxes—front, rear and intermediate —are employed in the transmission system. The rear-rotorgearbox receives power through a shaft connecting it to the intermediate gearbox which, in turn, is connected to the frontgearbox by a synchronizing shaft running in a duct along the top of the fuselage. Power is fed into the system from the front engine to thefront gearbox and from the rear engine to the intermediate gear- box, so that, in the event of one engine failing, power is suppliedto both rotors from the remaining engine. A freewheel unit between each engine and its respective gearbox ensures that nopower can be fed back into the "dead" engine. The front-rotor gearbox contains two stages of reduction gear-ing, which consist of internal and external spurs respectively. The freewheel is incorporated on the input shaft, together with aspiral bevel for the synchronizing shaft. The intermediate gearbox contains a pair of spiral bevel gears. Auxiliary drivesfor two alternators and an oil pump are taken through bevel gears, and the freewheel is fitted to the input side of the inter-mediate gearbox. The rear gearbox incorporates two stages of reduction gearing, comprising a first-stage spiral bevel gear anda second-stage spur gear. Oil from the supply tank is circulated to front, rear andintermediate gearboxes by means of pressure pumps in the intermediate gearbox. Circulation is completed by a scavengepump in the front gearbox and by gravity from the rear and intermediate gearboxes. A hydraulically operated rotor-brakeis fitted at the forward end of the synchronizing shaft. Rotor Hub and Blades. Light-alloy construction is used forthe constant-chord blades, each of which incorporates an extruded hollow D-section combined leading edge and spar.Aft of the spar the blade is made up of a number of separate sections bonded to the spar, each section comprising thin skins Transmission layout of the 792 follows 173 practice. The syn- chronizing shaft runs between the front and intermediate gearboxes, engine shafts to front and inter- mediate gearboxes respectively, and rear rotor shaft between intermediate and rear gearboxes. bonded to pressed ribs. Alternatively, wooden blades similar tothose of the Type 173 may be fitted. The rotor hub is similar to that currently being designed fordeveloped versions of the 173, with mechanical details based on the hub design used on the 171 and 173 prototypes, and isillustrated in the sketch above. Each rotor hub consists of a driving hub to which blade sleevesare attached through flapping and drag hinges. Centrifugal loads are transmitted from the blades to the drag hinges throughtie rods, which are constructed in eight segments to provide low torsional stiffness. Blade root bending loads are taken on lightjournal bearings, and drag-hinge and inter-blade dampers are fit- ted. Cyclic-pitch control is obtained by tilting a centrally mountedspider, and collective pitch is controlled by vertical movement of a cone carrying the spider in a spherical seating. Centrifugallyoperated droop and anti-coning stops are fitted, t® prevent blade sailing and excessive droop during starting-up and running-downin high and gusty winds. Operated by bob-weights restrained
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