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Aviation History
1940
1940 - 0654.PDF
MARCH 7, 1940 An accurate photograph of the transverse section of themiddle of an undercut tooth of a special bevel pinion taken by the Section Projector. light the profile oi the work placed in the field. The beamthen passes through a projection lens which forms an image of the profile and this is reflected upwards by an inclinedmirror and onwards to a second overhead mirror. This finally reflects the magnified image downwards onto a large horizontal screen 5ft. in diameter, where it can be examined and measured. The horizontal screen hasthree controls, duplicated for convenience on opposite sides, which are employed for focusing and positioning the image.One method of using the instrument for repetition examina- tion work is to place an accurate enlarged drawing on thescreen and then to project the image accurately into posi tion upon the drawing, when any divergences are madeapparent. The complete apparatus occupies a space of 11ft. 6in. by 7ft. 6in. on the floor, and 11ft. gin. high,and is constructed very rigidly Kso as to be unaffected byvibration. Perhaps the most marvellous of all these highly scientificmeasuring instruments is the Section Projector, for it can deal with work which otherwise cannot be measured withthe degree of accuracy necessary in modern production. Take, for example, the tooth of a helical bevel gear. Theends of the tooth are visible enough, but are of different size. What may be the exact profile in the middle of thetooth, or what is the profile in the plane of the rolling angle ? Such profiles cannot normally be projected becausethe curved flanks from end to end of the gear tooth obscure the field of view. The manner in which this job is tackledis extremely clever. By means of a special kind of illuminating system the Section Projector instrumentthrows a fine plane sheet of bright light across the tooth in the direction in which the section to be measured isrequired. A line of light is thus formed by the intersec- ting of the tooth with the plane of the sheet of light, andthis line traces the section of the tooth. The illuminated section thus obtained is then photo-graphed by means of a special camera whose lens may be positioned to view the section from a suitable oblique viewpoint. The camera has a specially devised lens system whose geometry is such that despite the obliquity of theview point, and the selection of one view point or another, the resulting unit size photograph is free from distortion,and is sharply defined all over the plate. The photograph can afterwards be magnified and projected on to a screen.ThiB instrument is even able to deal with pinion teeth which are undercut at the roots, as shown in the photo-graph reproduced. The STINSON MODEL 105 DETAINING the fixed wing slots, three-position flaps, •*-*• hydraulic brakes and the other characteristics embodied in the original model of 1939, the Stinson Model 105 for 1940 is an improved version with more power, higher cruising speed, faster take-off and climb, greater service ceiling and a full four-hour cruising range. Powered by an 80 h.p. Continental engine, the " 105 ' has a cruising speed of 111 m.p.h. at the optimum altitude of 4,800ft. It is also available with a 75 h.p. engine and this model is priced at $3,295 at the factory, Wayne, Michigan. Tt has a cruising speed of 107 m.p.h. at opti- mum altitude. The extra cost of the 80 h.p. model is only $75- The rate of climb on the new model has been increased 12 per cent, and now is 500ft. per minute. Service ceiling is increased 20 per cent, to 12,100ft. Ground handling in high winds has been improved by an increase in the size of the hydraulic brakes. A steerable tail wheel is also available. The engine cowling has been redesigned for easier accessibility and is now of the hinged automobile type. Other improvements include improved cabin venti- lation and additional capacity in the cabin heating system. Wins span Overall length Overall height Wing area Empty weight 34ft. 22ft. 2in. 6ft. Sin. 155 sq. ft. 900 1b. Specification Useful load Payload ... Gross weight Wing loading Power loading and Performance 680 lb. 382 lb. 1,580 1b. 10.21b. per sq.lt 19.81b. per sq. ft. Cruising speed at optimumaltitude of 4,800 ft. .. Rate of climbService ceiling Cruising rangeLanding run 111 m.p.h.500ft. permin. . 12,100ft.425 miles. 150ft.
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