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Aviation History
1915
1915 - 0051.PDF
JANUARY 15, 1915. [/ycHf] Edited by V. E. Models Driven by Compressed Air. Continued from page 33.) Heating tke Air. THIS point has already been dealt with to some extent, but there are one or two points to which further reference should be made. In the first place, the heating may be either direct or indirect. In the first case, the air from the reservoir in its path to the motor passes through a coil of tubing placed in the flame of a blow-lamp or vapour lamp, as the case may be. In the second case, the coil of metal tubing is surrounded by a suitable chamber or container nearly full of water, and it is this water which is directly heated by the lamp. As Mr. Hayden pointed out to the writer, in his case it would be impossible to use the direct or dry heat method because his leather cupwasher would at once shrivel up. In the case, however, where no leather cups, &c., are used, even with soft soldering a very fair amount of heat could be used. Soft soldering is, I believe, generally considered to be capable of standing a steam pressure of 100 lbs., provided any flame is kept well away from the soldered joints, &c. Owing to press of other work, the writer is compelled to postpone the experiments he intended to make in this direction, but the subject is undoubtedly one well worth experimenting with, and he trusts there will be no delay in the matter, but that some of the readers of FLIGHT will be able to carry out a little research work in this direction. It is, of course, a matter for bench testing, and therefore quite independent of weather conditions, and also very appropriate work for this time of the year. Soldering the Container. In the original steel container made by the writer, the flux used was zinc and spirits of salt ; in spite of every possible precaution, the container is now pitted with tiny pin holes and quite useless. By using brass or copper this difficulty is overcome, but steel is still used in the form of the steel wire wound around the container ; this should be soldered with " Fluxite." Fluxite is not so easy to use, but the writer has adopted a compromise by means of which the work can be done very quickly. For "timing" the soldering iron I use the old flux, and with a little streak of Fluxite smeared along the container and wire and the use of blowpipe solder, the soldering can be done very easily and quickly. Two Methods of Making the Container. There are two distinct methods ot forming the cylindrical con tainer : (i) by means of a straight longitudinal join or joins running from end to end, (ii) by means of spirally winding the metal foil on the wooden former. The latter method undoubtedly possesses some advantages, especially in the case when the diameter of the container would necessitate more than one longitudinal join. The method is also especially suited to the formation of the truncated cone type of container. It probably comes out rather the heavier of the two, but is undoubtedly the stronger. Testing for Leakages. This point has already been referred to, but I again raise it because I have reasons for believing that some consider it unneces sary to carry out a careful oil or water test. I can assure them that JOHNSON. M.A. they are absolutely mistaken ; you cannot hear little leaks or even feel them, but their presence makes all the difference in the results you will obtain. It is absolutely essential the most rigorous tests be made in this matter, and nothing but absolute airtightness be per mitted to pass. (To be continued.) Compressed Air Containers- Leslie Young, writing with reference to the above, 11. Mr. says :— " It may be of interest to you to know that I have constructed a very successful container, 22 ins. long by 2*5 ins. diameter, of very thin sheet tin, using copper half-balls (outside hilf) for the ends. " The joint is just an ordinary overlap with a strip of tin about 1 in. wide soldered over it. I evolved this joint after making two containers with S joints, both of which proved unsatisfactory, owing to the fact that the joint leaked badly (no matter how much solder was put on) with more than 100 pump strokes. The first of these two containers burst down the seam with only 100 strokes. " On the present container I have obtained 200 strokes, and I do not doubt but what more could be obtained, but I have not tried above this number so far. " The duration obtained with 200 strokes (autoplan pump) is app. 40 sec. using a horizontally-opposed oscillating engine, | in. bore by \ in. stroke, and a 12-in. Chauviere tractor. The engine was designed by Mr. H. J. V. Stevens (who is at present in training at Dorking with the Civil Service Rifles), and I think he is pre paring a few notes on same to send to you. " Below are particulars of cost of this container :— " Thin sheet tin, 20 ins. by 14 ins., t\d. ; 2 copper half-balls, 2'5 in. dia., 6d. (3d. each) ; solder, wire, valve, and tap, 2s. ; total, 2s. lod. Length, 22 ins. ; dia., z\ ins. ; weight (all on), between 9 and 10 ozs. " I am starting on a much smaller plant, to weigh about 7 ozs. with a single-cylinder piston valve engine, J-in. by J-in., and container, about 18 ins. by \\ ins., and I will let you have par ticulars with drawings when finished." A?romodelllsts Serving with the Colours. Epsom Aero Club. The Hon. Secretary of the above club, Mr. H. Ayles, Stanhurst, Epsom, writes us as follows :— " Noticing that you wish to publish the names of aeromodellists serving with the Colours, I give below a list of membeis of the above club now doing so :— " G. Butler, East Surrey (Territorials). " W. Coleman, Royal Engineers. " F. C. Corket, Royal Engineers. " H. Harlow, East Surrey. " A. Sanders, 8th Hussars. " The club has only been formed about six months, and the loss of these members reduces our numbers by nearly half. ,; I shall be glad if any aeromodellists in this district who would care to join the club will communicate with me." A CONTRAST.—A compressed air-driven Caudron biplane model by Messrs. D. Hiscox and C. Desoutter (on the left), and a flash steam-driven monoplane by Mr. H. H. Groves (on the right). Both are excellent examples of their respective types. 51
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