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Aviation History
1932
1932 - 0874.PDF
FLIGHT, AUGUST 26, 1932 3/ie SndwJmj RUBBER RING- A BOOST GAUGE YSTflTH all supercharged and high- compression aero engines it is necessary for the pilot to have an accurate knowledge at any moment of the absolute pressure in the induc tion pipe of the engine, and the Boost Gauge serves this purpose. An engine is designed for and gives its maximum output for a definite maximum induction pipe pressure, and a small pressure difference means a big difference in h.p. The efficiency of the supercharged engine is largely governed by the correct pressure in the induction pipe being maintained. Too low a pressure means loss of power, while excessive induction pipe pressure may seriously damage the engine. To avoid this the controls are usually arranged so as to give only a limited throttle opening on the ground and at low altitudes, but any subsequent control must be gauged by the pilot from the induction pipe pressure. This pressure is an absolute one, and is not affected by the pressure of the atmosphere surrounding the engine. An ordinary pressure gauge connected to the induction pipe would not give the indications required, as it would only show the difference between the pressure existing inside and outside the Bourdon tube or diaphragm move ment, whereas what is required to be known is the actual or absolute pres sure in the induction pipe irrespective of that of the outer air. Air Ministry Mark Ha Boost Gauge, made by Negretti and Zambra, of 38, Holborn Viaduct, E.C., is used in large numbers both in our own Air Force and several foreign air forces. The whole movement is contained in an airtight case with only one con nection, which leads to the induction pipe of the engine. When this is con nected up a reading is unaffected by any external barometer variation, and only shows the absolute or true pres sure in the induction pipe. The movement consists of two sets of exhausted nickel-plated tempered steel diaghragms operating a spindle on point bearings through a crank and 5 4^0LES ^f ^I6DIA Oh 3-9'p.cc The Negretti and Zambra Boost Gauge. link mechanism. Attached to the spindle a quadrant meshes with a pinion on the pointer spindle. On applying suction to the pipe connec tion, the diaphragms expand and operate the pointer through this geared mechanism. Provision is also made to withstand excessive over loads such as might occur when an engine backfires. Originally this instrument was made with an Aneroid Barometer movement, consisting of a nickel-silver diaphragm with a chain and pulley mechanism. This movement was found unsatisfac tory owing to the effect of vibration, position error, zero shift and general lack of reliability and accuracy. A "Power" cruiser with tropical awning. (FLIGHT Photo.) POWER BOATS FOR TROPICS A NUMBER of 30-mile-an-hour cruisers, equipped specially for operating in tropical conditions, are now being delivered by the British Power Boat Co. of Hythe to R.A.F. marine air bases abroad. Included in the equipment of these rescue cruisers is a closed cabin, which can accommodate a number of stretcher cases. The new tropical type rescue cruisers have copper bottoms and are fitted with large awnings to protect their crews from the heat of the sun. They are to be stationed at the R.A.F. seaplane bases at Aboukir, Malta, Basra and Singapore. Beacons for Transatlantic Air Traffic A REMARKABLE engineering feat, carried out in the face of almost insurmountable difficulties, has been per formed by the " Companhia Aga do Brazil," a subsidiary of the Swedish Aga Company, in building a lighthouse for aviation and shipping on a desolate reef a considerable distance off the Brazilian coast. The work was carried out on the almost inaccessible islands Penedos de Sao Pedro e Sao Paolo and it was primarily the needs of transatlantic aviation that decided the Brazilian Govern ment to have this lighthouse constructed. Owing to the great difficulty in landing on rugged and forbidding rocks the only possibility was to select an " Aga " beacon, the well-known invention of Dr. C. Dalen, the blind Swedish Nobel prize winner who lost his sight while experimenting with the accumulation of gas needed for these lights. The " Aga " beacons through an ingenious device, called the " sun-valve," function automatically, extinguishing themselves at daylight and switching on the light at dark or in a fog without being touched by a human hand for more than a year. When the gas mantle is burnt out it is automatically replaced. Besides this lighthouse, said to be one of the most powerful in the South American waters, a reserve beacon has been built on the same islands and constructed so as to function automatically if the main light should for some reason get out of order. A third " Aga " lighthouse intended for the same flying route has been built at Calcanhar in the State of Rio Grande del Norte at the point where the aviators arrive at the coast of Brazil. 1932 International Balloon Race THE International Balloon Race for the Gordon Bennett Cup will be held this year at Basle, Switzerland, and is to start on September 25. The Bennett Cup has been won nine times by the United States, five times by Belgium, twice each by Switzerland and Germany, and once by France. The original cup has been twice replaced, Belgium winning it permanently in 1924, the United States winning the second cup put up by the people of Belgium, and the third cup, now in competition, being offered by the Detroit Board of Commerce. A Signpost for Renfrew AIRMEN passing over Glasgow en route for Renfrew Aerodrome will now be helped by a direction indicator on the gasometer which stands on the south bank of the Forth and Clyde Canal at Temple. The container has been entirely recovered with aluminium paint. The crown of the container will be marked with a thick red line to indicate in which direction the aerodrome lies. Greenock has its name painted on the top of its gasometer. 810
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