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Aviation History
1933
1933 - 0863.PDF
OCTOBER 26, 1933 71 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT Flf^ 1 No ''i 1 1 X- POINT OF MAX.THICKNESS \ •28 29 30 r -31 32 33 34 1-3 1-2 10 K •y •5 •/ ru.j | y ri / /\ / i i i . i X,-POINT OF MAX.THICKNESS ! ! Mill ! i 1 •28 -29 3C •31 -32 -33 54 •6 •5 •4 HE C •3 •1 HG.b. \ft // j > i N Mil it / ' ! ! 1 ' ' ' ! 1 II PROFILE SHAPES i ! |Vj Ts I l i ps i i 1 Sc • 0 9315 t(l-X)(xW0-2961 xi) i N.AC A PROFILE 1 | ! 1 1 i i i i N^ \ 0 1 2 3 -4 -r -5 6 7 -8 -9 10 tube. This can easily be arranged for on any of the suggested family of curves by designing the profile for a chord slightly in excess of the required chord. The amount by which the design chord is in excess of the machine chord is given by Ac = Kt (a + 1) di (4) d1 = half depth required at T.E. (ins.) Then the chord for calculating profile is C+A<" = l-0. Probably a simpler way is to add to the half-ordinate- the amount d,ar, so that the finally adjusted profile is given by yt = Kt (1 —x) (xi + axi) + dxx2 (5) Where dt is in terms of the chord length. This small correction will not seriously affect the values of " K " and " a " already deduced. So far as the writer is aware, there are no published results of tests in the V.D. Tunnel showing the effect of moving the position of maximum thickness. Where structural considerations do not demand any thing abnormal in spar depths at any particular point along the chord, it would seem unwise to depart from the N.A.C.A. profile shape, or similar, having maximum thickness at 0.3 of the chord. The foregoing alternatives are only given to cover cases where this standard is not desirable, or possible. from structural considerations only. (To be continued.) REFERENCES 1 II. & M. 910. " A Theory of Thin Aerofoils." H. Glauert. B.A. 2 "The Estimation of Profile Dra<*." W. E,. Andrews. AIRCRAFT ENGINEER, June 17, 1932. i N.A.C.A. Technical Note No. 38S Aerofoils." E. N. Jacobs. ; Characteristics of Symmetrical 4 N.A.C.A. Technical Note No. 391. Jacobs and B,. M. Pinkerton. 5 N.A.C.A. Technical Note No. 392. E. N. Jacobs and B,. M. Pinkerton. 5 N.A.C.A. Technical Note No. 401. V.D. Wind Tunnel." E. N. Jacobs and K. M. Pinkerton. ' Characteristics of Aerofoils." E. N. "Aerofoil Tests in V.D. Channel." Tests on N.A.C.A. Aerofoils in the TOOL ROOM TEMPERING EQUIPMENT The letters " TET " are used to denote the Tool Room Tempering unit recently introduced by Wild- Rarfield Electric Furnaces, Ltd., of Elecfurn Works, London, N.7. That firm has, of course, had long ex perience in the construction of large furnaces with rorced-air circulation for production tempering, and this experience has been applied in the production of the new smaller unit, which, as its title implies, is intended for the simpler equipment of the tool room. -I wo models are available, one being suitable for tem peratures up to 400 deg. C. and the other up to 650 deg. C. The only difference between the two models hes in the design of the temperature regulator. The 400 deg. model is suitable for tempering carbon steel parts, while the 650 deg. pattern covers the 'whole ''(inge of tool-room tempering, both of carbon and of high-speed steels. The powerful air circulation pro vided by the centrifugal fan produces exceptionally rapid heating, and also a very uniform temperature. The running cost will, of .course, depend to some extent upon the locality in which the unit is installed, but it is claimed that in many cases the cost is definitely TEMPERATURE INDICATOR o COMPLETE SWITCHGEAR WORK BASKET .TEMPERATURE CONTROLLER INSULATION DIRECT DRIVE FAN MOTOR Sectional Elevation of Wild-Barfield " TRT " Unit. smaller than can be obtained with oil, lead or salt tempering baths which involve frequent replacement of the liquid. The maximum range of the outfit is 4 kw., but once the maximum temperature has been reached, the consumption is only about 1.5 units per hour. In order to combine the desirable features of rapid initial heating with close temperature control, a switch is provided on the panel, by means of which one sec tion of the heating elements may be cut out. By thus reducing the rating of the furnace, exceptionally close temperature control is provided, even at temperatures down to 200 deg. C, and it is claimed that the most delicate dies, press tools, milling cutters, etc., can be treated without the slightest risk of damage. The whole equipment has been designed with a view to the utmost simplicity in operation and installation. All connections between the furnace and its associated electrical gear are made before despatch, and the user is merely required to connect the mains supply leads to the switch panel, when the furnace is ready for imme diate operation. The chamber is cylindrical, lined with 1072 C
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