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Aviation History
1943
1943 - 2266.PDF
FLIGHT SEPTEMBER I6TH, 1943 GERMAN AIRCRAFT STRUCTURES 5ECTI0N A A OF RUBBER PAD Flexible engine attached by ball joints to fittings at the bottom of the engine bulk- head. There is no connection be- tween the two sides of the engine mounting except by their mutual attachment to the engine at two points on each side, one at the top of the engine about half-way along and one lower down towards the rear. The Me 210 engine mountings differ from those described above in having the main bearers attached to the bottom of the engine bulk- head and sloping up towards the front of the engine, with tubular tie-rods attached to fittings at the top of the bulkhead to support the bearers in this position. More- over, the bearers themselves are not magnesium forgings, but are each built up from a pair of hollow light-alloy stampings welded together to form rectangular- section members. Fig. 11 shows four types of engine mountings for liquid- cooled engines, including the Me 210 type. Radial;—In both the radial-engined machines, the Fw 190 and the Do 217, the engine mountings are of steel tubular welded construction. In the Fw 190 the design is novel in that the hexagonal mounting ring which is attached to the engine at ten points is of hollow welded construction, and forms a reservoir for hydraulic fluid. Flexible Mountings:—In all these types of engine mount- ings the engine is carried by the bearers through the medium of flexible rubber bushes. Fig. 12 shows a section through a typical mounting bush, that used in the Me no. The light alloy mounting boss is bolted rigidly to the engine and terminates in a journal. The thick lozenge-shaped rubber pads are pushed over the journal to form a saddle for the engine bearer. The rubber pads are held in place by a cap secured by a bolt through its centre to the mount- ing boss. Undercarriages A wide variation is apparent in the design of the under- carriage" of German aircraft. Fwiqo:—The Fw 190 undercarriage is high and has a very wide track. Each wheel .is carried at the-end of a single long oleo-pneu- niatic shock absorber leg with a leather con- certina eolfcr over the exposed part of the piston, ;uid triangular torsion links. The legs have a possible travel of nearly 15m. The top of each leg is in the form of a casting which incorporates a shaft, at right angles to the leg, which can rotate in two bearings, the front one in the main spar and the rear one carried about ift. farther back by two specially strengthened ribs. All the undercarriage drag loads are transmitted to the wing through these two bearings. Each leg has a hinged side stay, made up of two light-alloy forgings, which breaks at the centre and is folded by an electric motor, work- ing through a reduction gear box. The legs are drawn inwards and upwards by the side stays into wells in the underside of the wing. A photograph of this undercarriage is shown in Fig. 13. A compensating ram filled with air at 95 atmospheres works on the final drive shaft of the electric motor so that as it passes top dead centre in either direction the ram helps to ensure that the undercarriage goes right home in either the up or down position. REAR BEARER^ | mountingMe no. of D.B. 601A in Mechanical locks are provided in the retracted position but in the extended position locking is de- pendent on the end hinge points and the breaking hinge of the side stay being in line and held there by the ram. The tail-wheel retraction mechan- ism is ingenious. The oleo leg is mounted with its piston at the top and the wheel is carried in a fork at the bottom of the cylinder. The lower end of the cylinder is carried at the end of a forked link pivoted to a point farther forward in the fuselage. The top of the oleo piston is fitted with a crosshead carrying two pairs of rollers which > slide in a pair of vertical channels inside the fin, so shaped that in its lowest position the crosshead is turned over by a spring and is un- able to slide up the channels. A cable passing over a series of pulleys connects the crosshead to one of the links in the starboard main undercarriage and when this cable is pulled the crosshead is rolled over into line with the channels and can then be drawn up. When the cable tension is relaxed a spring pulls the rollers down the channels and locks them in the lowest position. The tail wheel fork is rotatable through 360 deg. but is centred by a hairpin spring and can be locked centrally by a plunger operated by the elevator controls when the stick is pulled right back, fhe tail wheel retraction and locking mechanism is shown in Fig. 14. D021J :—In the Do 217 each of the two main wheels is carried in a twin oleo portal frame, braced by tubular members, which folds backwards into the engine nacelle. Raising and lowering of the undercarriage is accomplished by a 1 h.p. electric motor mounted on the back of the rear centre-section spar. Power from the motor is transmitted by a hollow shaft running transversely across the aircraft at each end of which is a pair of bevel gears driving a screw jack which moves the portal frame by a linkage. The tail wheel is carried in a cast fork and is retracted through an opening in the underside of the fuselage which is then closed by doors. The tail wheel unit is retracted by Fig. 13. Fw 190 main undercarriage.
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