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Improved Jack for Load Tests

Improved Jack for Load Tests Workshop and Production Section AIRCRAFT ENGINEERING December, 1932 Japanese Modifications to the Standard Type N carrying out load tests on aeroplanes a t the steel plate partition separating the two springs. which rotates about the centre of a dial (10) Aeronautical Research Institute at Tokyo, These springs support a piston (4) and a made of fibre. The graduations (8) on the dial the ordinary motor-car typ e of jack used was receptacle (11) for holding the wooden block consist of shor t lengths of copper wire embedded found to have certain disadvantages liable to tha t comes in contact with the object to be in th e fibre, and when the pointer coincides with lead to overstressing of the spars in th e destruc­ tested. The displacement of the piston is one of these graduations, the circuit connecting tio n test and possible reversal of stress in the indicated by means of a rack-and-pinion (5) (6), th e terminal (9) on th e dial and some electric cells elastic test. Certain modifications to the jack an d a pointer (7) made of thin copper plate, wit h the lamps on a lamp board are short- used, which has a capacity of 2,720 k.g. (5,800 circuited. When there are no external forces lb.) and a stroke of 20 centimetres (7⅜ in.), a t work on the jack, the position of the pointer were therefore made, which are described in the corresponds to —1 of the graduation. When a Institute' s Report No. 78, July 1932. As ver y small force is exerted on the head of the these seem likely to be of general interest they jack by its coming into contact with the object are reproduced here. The jack's mechanism tested, the weaker spring is compressed and was altered somewhat by inserting a long steel moves the pointer to 0 on the dial, and, as the rod and a universal coupling between the re­ head of the piston comes into contact with the volving handle and th e jack itself, thu s enabling plate separating the two springs, the first lamp th e operator to work it without noise and with is lighted. Thenceforward the stiffer spring considerable free play for the handle so that alone receives the force of the object tested. he could work from any angle. Furthermore, The stiffness of the springs in the jacks thus th e joint between the rod and the universal improved was 1 kg . per millimetre for th e stiffer coupling, and that between the handle and the spring and 0·1 kg. per millimetre for the weaker. rod, are made readily detachable to prevent A piston displacement of 1 millimetre moves injury to the operator should destruction of the th e pointer one unit graduation, while a pointer tested object cause upsetting of the jack. movemen t of 41 mm . means that the piston The improved part of the jack is seen in detail has hit the cylinder. The five terminals are in Fig. 1. The cylinder (3) is screwed into the connected to graduations 0, 2, 5, 15, and 30, telescoping body of the jack. In the cylinder a respectively, and when the position of the fairly stiff helical spring (1) is inserted, and pointer coincides with any one of these gradua­ abov e it a very flexible spring (2) is added, a tions, one of the lamps on the board is lighted. Each vertical row of lamps on th e lamp board * Extracted from Report No. 7S of the Japanese Aeronautical is connected to a different jack. Research Institute. More Hints on Airscrews brigh t and all traces of the black deposit are Corrosion and Erosion of Metal Blades Etching Aluminum Alloy Airscrew Blades removed. These operations will be repeated Whe n duralumin airscrews encounter salt I t is good practice to carry out the etching until the desired depth of etch is obtained. air, a light film of aluminum hydroxide is process about every 300 to 350 hours of flying After the etching process is completed, the formed on the surface. This appears as a fine time . The purpose of etching is to clean the airscrews should be examined thoroughly for white powder and in itself does little harm. surface of the metal, and show up any cracks an y minute hairline cracks which may have I t is best removed by wiping the blade with which may have started as a result of continual started as the result of repeated stresses in the a rough cloth, followed by rubbing with a coat use. In order to carry out the etching process, blades. Cracks of a dangerous nature are of oil. Ordinary old oil drained from aero­ it will be necessary to prepare the following usually at right angles to the length of the engines proves very effective, as th e free carbon solutions:— blade, and usually start as very small cracks in it acts as a mild abrasive and the trace of (a) Caustic Soda Solution: to each gallon and gradually grow as the use of the airscrew sulphuric acid in the oil removes the hydroxide of water, add one to two pounds of com­ is continued. While there is very little likeli­ deposit, while the oil film left on the blade mercial caustic soda. This corresponds to hood of cracks developing in any of the present keeps the air from it. a ten to twenty per cent. aqueous solution. designs, this procedure is recommended as an (b) Nitric Acid Solution: to each five additional safety precaution. gallons of water, add one gallon of com­ Glare from Airscrew Blades mercial nitric acid. This corresponds to a Glare is caused by the direction of flying twent y per cent. aqueous solution. Straightening Alloy Airscrew Blades relative to the sun, the altitude of the sun, the I t is essential that wood, glass or earthen­ height of eye of the pilot relative to the axis ware containers be used for both the caustic I t is usually possible to straighten aluminum of the airscrew and the distance of the pilot's soda and nitric acid solution. In mixing the alloy airscrew blades which have been bent or eye from the airscrew disc. When necessary, acid, always pour the acid slowly into the twisted in a minor accident. If the deformation th e "face " of the blade may be covered from water. Rubber gloves should be worn at all is very slight, the blades can be straightened by th e tip to about the 20 in . radius with a good a qualified engineer. If, however, the deforma­ times while working with these solutions. grade of varnish to which some colouring dye tion is considerable, it is necessary to anneal Where there are only a few airscrews to (aniline) has been added. The most effective th e blades before re-forming to approximate inspect, the following procedure may be colours are dark brown, deep blue or black. shape, the n to heat-treat and finally to complete adopted: — The coating should be applied very thinly and th e straightening. The straightening of serious Small quantities of the caustic soda solution all blades of the same airscrew coated as nearly deformations requiring annealing and heat may be applied to the airscrews by means of alike as possible to preserve balance. It is swabs or fibre brushes. A convenient swab is treatmen t should never be attempte d except by not necessary to cover the whole blade, as it is provided by cotton rags wound around a wooden th e manufacturer. After straightening, the desirable to keep as much uncovered metal blades should be etched and examined for stick approximately two feet in length. The as possible in order that better inspection can cracks or surface defects. The hubs should whole surface is well blackened, rinsed immed­ be had. also be checked for cracks and deformations iately with water and swabbed in similar before the airscrew is pu t back into service. H . E . F . manner with a nitric acid solution until it is http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

Improved Jack for Load Tests

Aircraft Engineering and Aerospace Technology , Volume 4 (12): 1 – Dec 1, 1932

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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb029638
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Abstract

Workshop and Production Section AIRCRAFT ENGINEERING December, 1932 Japanese Modifications to the Standard Type N carrying out load tests on aeroplanes a t the steel plate partition separating the two springs. which rotates about the centre of a dial (10) Aeronautical Research Institute at Tokyo, These springs support a piston (4) and a made of fibre. The graduations (8) on the dial the ordinary motor-car typ e of jack used was receptacle (11) for holding the wooden block consist of shor t lengths of copper wire embedded found to have certain disadvantages liable to tha t comes in contact with the object to be in th e fibre, and when the pointer coincides with lead to overstressing of the spars in th e destruc­ tested. The displacement of the piston is one of these graduations, the circuit connecting tio n test and possible reversal of stress in the indicated by means of a rack-and-pinion (5) (6), th e terminal (9) on th e dial and some electric cells elastic test. Certain modifications to the jack an d a pointer (7) made of thin copper plate, wit h the lamps on a lamp board are short- used, which has a capacity of 2,720 k.g. (5,800 circuited. When there are no external forces lb.) and a stroke of 20 centimetres (7⅜ in.), a t work on the jack, the position of the pointer were therefore made, which are described in the corresponds to —1 of the graduation. When a Institute' s Report No. 78, July 1932. As ver y small force is exerted on the head of the these seem likely to be of general interest they jack by its coming into contact with the object are reproduced here. The jack's mechanism tested, the weaker spring is compressed and was altered somewhat by inserting a long steel moves the pointer to 0 on the dial, and, as the rod and a universal coupling between the re­ head of the piston comes into contact with the volving handle and th e jack itself, thu s enabling plate separating the two springs, the first lamp th e operator to work it without noise and with is lighted. Thenceforward the stiffer spring considerable free play for the handle so that alone receives the force of the object tested. he could work from any angle. Furthermore, The stiffness of the springs in the jacks thus th e joint between the rod and the universal improved was 1 kg . per millimetre for th e stiffer coupling, and that between the handle and the spring and 0·1 kg. per millimetre for the weaker. rod, are made readily detachable to prevent A piston displacement of 1 millimetre moves injury to the operator should destruction of the th e pointer one unit graduation, while a pointer tested object cause upsetting of the jack. movemen t of 41 mm . means that the piston The improved part of the jack is seen in detail has hit the cylinder. The five terminals are in Fig. 1. The cylinder (3) is screwed into the connected to graduations 0, 2, 5, 15, and 30, telescoping body of the jack. In the cylinder a respectively, and when the position of the fairly stiff helical spring (1) is inserted, and pointer coincides with any one of these gradua­ abov e it a very flexible spring (2) is added, a tions, one of the lamps on the board is lighted. Each vertical row of lamps on th e lamp board * Extracted from Report No. 7S of the Japanese Aeronautical is connected to a different jack. Research Institute. More Hints on Airscrews brigh t and all traces of the black deposit are Corrosion and Erosion of Metal Blades Etching Aluminum Alloy Airscrew Blades removed. These operations will be repeated Whe n duralumin airscrews encounter salt I t is good practice to carry out the etching until the desired depth of etch is obtained. air, a light film of aluminum hydroxide is process about every 300 to 350 hours of flying After the etching process is completed, the formed on the surface. This appears as a fine time . The purpose of etching is to clean the airscrews should be examined thoroughly for white powder and in itself does little harm. surface of the metal, and show up any cracks an y minute hairline cracks which may have I t is best removed by wiping the blade with which may have started as a result of continual started as the result of repeated stresses in the a rough cloth, followed by rubbing with a coat use. In order to carry out the etching process, blades. Cracks of a dangerous nature are of oil. Ordinary old oil drained from aero­ it will be necessary to prepare the following usually at right angles to the length of the engines proves very effective, as th e free carbon solutions:— blade, and usually start as very small cracks in it acts as a mild abrasive and the trace of (a) Caustic Soda Solution: to each gallon and gradually grow as the use of the airscrew sulphuric acid in the oil removes the hydroxide of water, add one to two pounds of com­ is continued. While there is very little likeli­ deposit, while the oil film left on the blade mercial caustic soda. This corresponds to hood of cracks developing in any of the present keeps the air from it. a ten to twenty per cent. aqueous solution. designs, this procedure is recommended as an (b) Nitric Acid Solution: to each five additional safety precaution. gallons of water, add one gallon of com­ Glare from Airscrew Blades mercial nitric acid. This corresponds to a Glare is caused by the direction of flying twent y per cent. aqueous solution. Straightening Alloy Airscrew Blades relative to the sun, the altitude of the sun, the I t is essential that wood, glass or earthen­ height of eye of the pilot relative to the axis ware containers be used for both the caustic I t is usually possible to straighten aluminum of the airscrew and the distance of the pilot's soda and nitric acid solution. In mixing the alloy airscrew blades which have been bent or eye from the airscrew disc. When necessary, acid, always pour the acid slowly into the twisted in a minor accident. If the deformation th e "face " of the blade may be covered from water. Rubber gloves should be worn at all is very slight, the blades can be straightened by th e tip to about the 20 in . radius with a good a qualified engineer. If, however, the deforma­ times while working with these solutions. grade of varnish to which some colouring dye tion is considerable, it is necessary to anneal Where there are only a few airscrews to (aniline) has been added. The most effective th e blades before re-forming to approximate inspect, the following procedure may be colours are dark brown, deep blue or black. shape, the n to heat-treat and finally to complete adopted: — The coating should be applied very thinly and th e straightening. The straightening of serious Small quantities of the caustic soda solution all blades of the same airscrew coated as nearly deformations requiring annealing and heat may be applied to the airscrews by means of alike as possible to preserve balance. It is swabs or fibre brushes. A convenient swab is treatmen t should never be attempte d except by not necessary to cover the whole blade, as it is provided by cotton rags wound around a wooden th e manufacturer. After straightening, the desirable to keep as much uncovered metal blades should be etched and examined for stick approximately two feet in length. The as possible in order that better inspection can cracks or surface defects. The hubs should whole surface is well blackened, rinsed immed­ be had. also be checked for cracks and deformations iately with water and swabbed in similar before the airscrew is pu t back into service. H . E . F . manner with a nitric acid solution until it is

Journal

Aircraft Engineering and Aerospace TechnologyEmerald Publishing

Published: Dec 1, 1932

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