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Aviation History
1957
1957 - 1107.PDF
FLIGHT, 9 August 1957 SPRING-LOADED SPHERICAL SEALS ROTODYNE... (Left; Tfce "#ni/k cfcurn" fabri- cated /rom sheet, which ducts air to opposing blade-spar roots. weighs 622 1b, plus the tip jet at 45 lb) are taken through therear spar fitting. A cuplike machined forging "gathers" the separate spar fitting loads and transfers them to the inner spar, towhich it is attached by an internal ring nut. This inner spar is a thick-walled mace-shaped tube machinedfrom a solid S.99 forging. Its bore connects the rotor head air- delivery to the three blade ducts by way of a neat little weldedstainless steel "trifurcated" duct. The root cup of the inner spar fits over the bearings of the flapping-hinge fork and pitch-changeaxle assembly. On the outside of die inner spar are clipped the fuel supply line and the ignition loom. The rotor blade is completed by 24 light-alloy trailing-edgeboxes with 30 s.w.g. skin. To allow for differential expansion and blade flexing, each box is fastened to the spar at its inner endonly, the outer end being free to float on a pin and slot. The electrical loom is threaded through plastic tubes let into the ribsof the trailing-edge boxes. Rotor Mountings. The rotor is carried on a bolted H.T. steel-tube (T.60) four-legged "tower." The streamlined fairing round this structure is anchored only to the four fuselage fittings forthe "tower," otherwise it is fully floating so as to allow for strain in the tubular structure. On die top of the tower are four pairs oftriangulated tubes, the four apices of which carry the main bearing housing. This last is a 30-in diameter circular channel boxedon its underside by a bolted steel plate. Air Delivery. The air from each Eland feeds only one pair of(opposing) rotor blades, so that in the event of engine failure the efficiency of the system is not impaired. The leading-edgeair ducts are fabricated by spot welding from Nimonic 75 sheet, using a crimped, or bellows, form to allow for thermal expansion.When the ducts reach the rotor pylon there is the problem of maintaining separate delivery into the rotating head. To achieve Rotor pitch control (airflow omitted for clarity—see sketch above):Rocking movement applied by paired jacks to the lower set of inclined bearings on the concentric control tubes imparts a rotary motion to the vertical tubesand a corresponding rocking of the upper set of inclined bearings, thus tilting the spider. Collective pitch is obtained by both upper jacks moving in thesame sense. The inner tube is splined to allow this vertical movement of outer tube and spider. Small diagram shows principle of inclined bearings. FUEL DISTRIBUTOR YOKE AND GIMBALTO PREVENT ROTATION OF OUTER GIMBAL FORE AND AFT CYCLIC -AND COLLECTIVE-PITCH JACKS AND INCLINEDBEARING LATERAL CYCLIC-PITCH JACKS AND INCLINED BEARING Air from the port auxiliary compressor enters the inner duct of the light-alloy "trouser" casting and the starboard compressor supplies the annular duct around it. The sketch also indiciates some of the sealing problems involved in leading pressurized air at 250 deg C through flexing ducts. Note also the spar-root taper roller bearings. this a light alloy casting, known not unnaturally as the "breechespipe," accepts the two air flows in its "legs" and delivers them through concentric annuli which feed into the "milk churn."This is a fabricated Nimonic sheet assembly reminiscent of a Coles chimney cowl. The "churn" is a concentric annular duct mounted in therotating rotor-hub which ingeniously delivers the air from each duct to opposing pairs of blades. With the help of cascades toturn the flows and careful matching of cross-sectional areas the duct losses have been kept low. The rotating joint between the"breeches pipe" and the "churn" is sealed by a graphite- impregnated sintered bronze ring. Dividing me two flows—normally widiout a pressure drop, but vital after engine failure— is a labyrinth seal. Up the centre of the assembly is the airtighttube within which the concentric control tubes operate; and at the centre of everything is die conduit for fuel pipes and ignitionleads. The combustion system cannot be described in detail here, butthe principles, and die development history, were fully dealt with in Flight for May 3 (page 575). Rotor Head. The basic problem in die rotor head was how toget die pitch-change controls round the obstruction offered by the air ducting. It was solved by mounting die actuatinglinkages and swashplate on top of the rotating head, with the operating jacks anchored below die main bearing housing, theaction being transmitted by concentric slide/torque tubes. The high-tensile-steel central rotor forging rests in die doubletaper-roller main bearing, in which it is locked by a large ring nut. On die bottom of die forging is mounted a toothed ringwhich drives die pinion and shaft to die auxiliary gearbox and rotor brake. Bolted to me upper part of die central forging aredie stub arms which hold die flapping hinges. These are large journal bearings that mate widi the flapping-hinge fork and pitch-change axle assembly inside die cup-shaped root of die inner spar. The axle assembly is composed, in effect,of concentric sleeves widi a double taper-roller thrust bearing for the c.f. loads and two double/taper-roller feadiering bearings.Inside die flapping-hinge fork there is a hemispherical self- centring joint for die air duct.The two pairs of control jacks—with tandem pressure chambers fed continuously by main (duplicated) and emergency hydraulicsupplies—act on sliding collars mounted on hemispherical bosses on die actuating tubes. The upper collar rotates the outer of dietwo control tubes to displace, through its canted head, the fore- and-aft cyclic-pitch linkage, while die lower one similarly operatesdie lateral cyclic-pitch linkage through the inner tube. The two "fore-and-aft" jacks operate togedier to raise and lower die swash-plate (which has a driving link to one rotor-blade stub arm only) to give collective pitch change. A splined extension at die footof die operating tube allows vertical displacement for collective- pitch control widiout affecting die lateral cyclic-pitch jacks.The various bearings in the control head are supplied widi oil, die unit being sealed by two bellows. The oil drains back to asump, from which it is pumped by die rotor-gearbox pump. The main bearing is likewise supplied by oil from diis gearbox.The central tube to die top of die rotor head carries a conduit containing the fuel lines, ignition leads and light-up telltale leadsto die fuel distributor manifold and respective sliprings. On die prototype diere are many additional wires for the strain-gauges,which, of course, are picked up selectively as the test programme is followed. J. H. S.
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