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Aviation History
1935
1935 - 1114.PDF
528 FLIGHT. MAY 16, 1935. screwed joint, and a steel band having two fins is pressed on to the lower end of the head to reinforce the joint and to prevent any leakage or pressure at work ing temperatures. The heads have horizontal fins, and each carries two valves, inlet and ex haust, being alike and inter changeable. They are of high nickel high chromium steel and operate in hard phosphor-bronze guides. Two bosses on the top of the cylinder head are provided for stud attachment of brackets to support a ring cowling. The valve seats are screwed and shrunk into the cylinder head. The valves are operated by rockers carried on hardened steel needle roller bearings. The end of the rocker which makes con tact with the valve stem is pro vided with a hardened steel roller running on a hardened steel pin. Double springs are provided for each valve and the valve stems have hardened ends to reduce wear due to the action of the rocker. The whole of the rocker gear on the cylinder head is enclosed by two pressed aluminium covers of streamline form, attached by self-locking thumb screws Grease-gun lubrication is provided for the rockers. At the lower end of the cylinder is a deep spigot and a flange, and attachment to the crank case is by means of four substantial steel clamps held by studs in the case. Two spark ing plugs per cylinder, carried in bronze adaptors, are fitted. An additional boss is provided which can be used for fitting either a compressed air or gas starter valve. Connecting-rod Assembly and its carrier for valve timing. The tappets, which are car ried in long bronze guides, are actuated by the cam via roller- ended rockers pivoting on hardened steel spindles attached to the front wall of the crank case. The push rods are of tubular form and provided with hardened steel cups at each end. They are enclosed in aluminium tubes, an effective oil seal being provided at the crank case end by cups covered by oil-resisting rubber sleeves. Included in the induction sys tem is a fan revolving at 3.8 times the speed of the crank shaft. A spring drive is incor porated which prevents shock from being transmitted to the fan when sudden changes of engine speed occur. A rearward tubular extension of the crank shaft possesses considerable flexi bility and in itself produces a considerable degree of damping. The fan shroud has a rearward projection in the form of a sleeve concentric with the driv ing shaft and running over it. A gear on the crankshaft exten sion provides gearing-up by an intermediate gear placed above it, this gear containing a centrifugal type of clutch which slips under sudden changes in load. From this intermediate gear a further step-up in gearing is provided for the sleeve of the induction fan, as shown in the accompanying drawing. Although a fan running at nearly four times engine speed is not to be regarded as a supercharger, it does provide slight positive pressure in the induction pipes, buts its object is to serve as a mixer in order to obtain good distribution. The carburetter recommended by Wolseley Motors is an S.U. type A.V.18, which is operated by a single throttle lever, the altitude control being entirely automatic. Altitude correc- capsule similar to those used ven M.agnetos by two B.T.H. magnetos of the fan induction casing close to the n of spring drive is incorporated, 8 clock-type spring, the outer end •eve secured to the driving shaft, while the other end engages with an extension of the mag- nAo driving bevel. A stop is provided to limit the amount of angular displacement. A dry-sump lubrication sys- t( m is employed, both pres sure and scavenge pumps being assembled as a unit and driven at engine speed from the rear end of the tail shaft. The pumps are of the spur gear type, the driving gears being of steel and the driven gears of phosphor-bronze. The pressure pump delivers 2.26 gallons of oil per hour at normal engine speed, while the scavenge pump has a capacity of 4.02 gallons per hour. The pressure pump casting has a Tecalemit filter chamber containing a fabric- covered filter element of ample size. The interior of the filter element contains a relief valve which opens when the difference in pressure be tween the inside and outside of the filter exceeds 6 lb. per sq. in. The filter can readily be removed for cleaning and the normal running period The connecting-rod assembly comprises the usual master rod and auxiliary rods. All are of H-section and produced from 65-ton alloy steel. Hard phosphor-bronze bushes are used for both the gudgeon-pin and wrist-pin ends. The auxiliary rods are attached to the master rod big end by hardened steel wrist-pins, at one end of which is formed a taper which fits into a correspondingly formed hole in one web of the master rod. The pistons are heat-treated aluminium alloy drop forgings and are of the fully skirted type. They are machined all over, and each is provided with two compression rings and two scraper rings, one of the latter being of the oil control type. Radial holes are provided at each of the scraper rings for the return oil. The hardened gudgeon- pin is arranged to float both in the small end of the con necting rod and in the piston bosses. Endways movement of the gudgeon pin is pre vented by circlips. A very simple valve- operating gear is employed. A single four-lobe cam is used, driven at one-eighth engine speed and in the same direction as the crankshaft. The drive for the cam is-by means of a double train of hardened steel spur gears, the layshaft and the cam carrier both running on ball bear ings. As a single cam operates both the inlet and the exhaust valves, the valve period is the same for both. To provide a fine angular adjustment of the timing a vernier attachment is pro vided between the cam gear tion is controlled by a corrug in aneroids. Spring-dri' Dual ignition is provided S.G.7 type, attached to the crank case. A patented forr and takes the form of a largi of which is attached to a sl( A cylinder head of the "Aquarius " with the rocker cover removed. Bosses for cowling brackets are incorporated in the casting. Details of the induction fan drive of the " Aquarius." The fan is mounted on a sleeve which is driven through the medium of the shock-absorbing centrifugal clutch pinion.
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