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Aviation History
1910
1910 - 0851.PDF
OCTOBER 15, 1910. The crank-chamber consists of a one-piece aluminium casting, which is strong and light in construction, for it is well ribbed on the inside by the brackets that carry the five large ball bearings on which the crank-shaft is supported. These bearings slide in place with the crank-shaft and are centred by set-screws from the outside. [pjGHT] " Flight " Copyright. Detail view of the 8-cyl. E.N.V. engine, showing the cap of the distributor removed in order to illustrate how the contacts, A1, and the feeder-brush, A, can be inspected without disconnecting the wires. Beneath the crank-chamber is a detachable aluminium box forming an oil sump. On one end of the crank-chamber is a detachable aluminium casing forming a cover-plate over the gear-wheels that drive the cam-shaft and pump. The other end of the crank- chamber is closed by the casing, which encloses the two ball -thrust races that enable the engine to drive either a propeller or a tractor-screw. The crank-shaft is of the four-throw type, and in appearance looks like one that might have been constructed for a 4-cyl. engine. The crank - pins are somewhat wider than usual, however, since each crank-pin accommodates the big-ends of two connecting-rods belonging to opposite cylinders. A special nickel chrome vanadium steel, having a tensile strength of 80 tons per sq. in., is used for the construction of the crank shaft, which is about ij ins. in diameter, and is bored hollow with a hole that is about I in. in diameter. Five ball-bearings support the crank-shaft in the crank- chamber, and the crank-webs are so shaped as to permit of the bearings being threaded on to the shaft. The journals on the crank-shaft have not been made especially large for this purpose, and the ball race is held on the shaft by means of two half-bushes that are adjusted in place when the ball bearing has been set in its proper position. These half-bushes somewhat resemble bearing-brasses, but they are made of steel, and are flanged at one end only. They slide in between the journal and the ball-race from opposite sides of the bearing, the presence of the crank-web preventing any other method of adjustment. The connecting-rods are steel stampings, and are drilled hollow with a hole about §-in. in diameter extending from the big-ends to within a short distance of the gudgeon-pins. This gives the connecting-rods a hollow oval section. The big-ends have white metal bearing surfaces poured straight on to the steel. The caps are held in place by two bolts. The gudgeon bearings are bushed with hardened steel tubes. Steel pistons are used, and great care is taken in machining them all over so as to reduce weight. The era-shaft, like the crank-shaft, is cut from the solid and is made of 6 per cent, nickel steel. It is about I in. in diameter, and the cams, which are being cut on a machine that has been specially designed for the purpose, are about J in. in width. The gear-wheel, by means of which the cam-shaft is driven by the crank-shaft, is cut from selected mild steel, and the teeth are about •& in. in width, so that it will be recognised that this member, which is characteristic of other features in the design of the engine, shows a combination of lightness and strength in a marked degree. Steel journals running in plain phosphor-bronze bushes form the supporting members of the cam - shaft, which is enclosed in a separate tubular chamber formed in the upper part of the crank- chamber. The cams operate direct upon large steel balls, similar to those used in ball bearings, which are held in hardened steel guides that screw into the crank - chamber. These steel guides carry phos phor - bronze guides, which are forced into place under hydraulic pressure, for the valve push - rods, the latter being simple steel rods parallel in section from one end to the other. The push - rods rest on the balls and abut direct upon the valve - stems, which means that a high degree of accuracy has to be maintained in manu facture in order to ensure two such very slender members coming into proper alignment. In ordinary motor car con struction it is common practice to fit a head of some sort on to the tops of the push-rods, in which case it is relatively unnoticeable if the axis of the valve-stem is slightly displaced, but in the E.N.V. flight engine the slightest discrepancy is noticeable immediately. The valve-stems themselves ride in hardened steel guides, which are screwed into the cylinder-casting, " Flight " Copyright. Detail view of the 8-cyl. E.N.V. engine, showing the gear-wheels that drive the cam shaft. Attention is drawn to the narrowness of the teeth of these members, which are only about §-ln. wide. The crank-shaft is sup ported on ball bearings, and one of them is visible immediately behind the lower gear wheel. The eccentric boss of this gear-wheel drives the plunger oil-pump. " Flight " Copyright. View of the base-chamber of the 8-cyl. E.N.V. engine. This is a one-piece casting in aluminium, and supports the crank-shaft on ball - bearings. The crank - shaft is in place, and the connecting-rods are seen projecting from the cylinder holes. Two connecting-rods are attached to each crank-pin. and abut against specially-shaped washers that conform to the contour of the casting. The valves themselves are of nickel steel, and have a small ring of pure nickel electrically welded on their seatings, this metal having been found to prolong the life of the 849
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