FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1951
1951 - 0512.PDF
temi-diagrammatic illustration of flying- and-engine control transmission linkage. The linkage motions for the several con- trol functions are explained in the text. BRISTOL 173 ... a synthetic-rubber ring of splayed channel-section which, bonded to the steel bearing housing, acts both as an a.v. mounting and a dirt excluder as well. This duplex cushioning in the shaft mounting should certainly help to alleviate the cabin noise problem. Beyond the fact that its axis is inclined rearward at seven degrees, the engine installation at the rear is precisely similar to that at the front. The points of dissimilarity in the trans- mission system are that the main output shaft from the engine connects into an intermediate gearbox which incorporates a similar free-wheel assembly to that used in the forward installation, and to which the drive-transfer and synchroniz- ing-shaft is engaged through similar spiral bevel gears. A subsidiary bevel pinion on the main vertical shaft of this intermediate gearbox gives drive port and starboard to a pair of quill-shaft assemblies through which torque is transmitted to a pair of generator/blowers bolted direct to the gearbox casing. The shaft of each Rotax generator is serrated to a centrifugal impeller which draws its air through a double venturi into the first throat of which the supply pipe to the vacuum instruments is vented. This extremely clever arrangement ensures that the suction-operated flying instru- ments are not deprived of vacuum even when the rotors are autorotating; a double venturi is employed so as to attain the pressure drop (circa 8oin water gauge) needed to compensate for pipe losses. The output from the impellers is passed through and around the generators and is then vented into the engine compartment. As this output is of the order of 150 cu ft/min from each generator, it is foreseen that it might well be turned to use for cabin heating; in this event, a heat exchanger either of exhaust-muff or surface-combustion type will be used. From the intermediate gearbox the main power trans- mission up to the rear rotor gearbox is through an extension shaft, similarly mounted in eight-point Layrub couplings. Essentially, the gearbox for the rear rotor is similar to its forward complement, with the basic difference that the input is to a bevel shaft which transfers drive to the layshaft, and so eliminates the use of an internally-toothed ring gear. Immediately beneath the layshaft is a sump, the integral oil pump for which is driven by a short vertical shaft serrated to the heel of the layshaft. An enormous advantage possessed by the 173, and one which should contribute in large measure to the early success of the aircraft, is the use, to a practicable maximum, of components already fully developed with the single-rotor 171 Sycamore. Beyond the fact that the rotors are handed (and thus the hub of the front rotor is a reversed image of that of the rear rotor), the detail design is identical with that of the 171. Since we described the 171 (October 30th, 1947) there have been only minor detail changes in the rotors which, briefly, are as follows : the blade shanks have been shortened ioin, and the six-segment tie-bars have been changed to eight-segment units in order to maintain the natural torsional frequency for the shortened length. Tapered pins are now used for blade anchorage to the shank to increase
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
