Thermal Analysis of As-received and Clinically Retrieved Copper-Nickel-Titanium Orthodontic Archwires

Objective: To compare as-received copper-nickel-titanium (CuNiTi) archwires to those used in patients by means of differential scanning calorimetry (DSC). Also, the thermal or phase properties of 27°C, 35°C, and 40°C CuNiTi archwires were studied to ascertain if their properties match those indicated by the manufacturer. Materials and Methods: Six wires of 27°C, 35°C, and 40°C CuNiTi were tested as-received, and six each of the 27°C and 35°C wires were examined after use in patients for an average of approximately 9 and 7 weeks, respectively. Segments of archwire were investigated by DSC over the temperature range from −100°C to 150°C at 10°C per minute. Results: There were no significant differences between as-received and clinically used 27°C and 35°C wires for all parameters (heating onset, endset, and enthalpy and cooling onset, endset, and enthalpy), except the 27°C wires exhibited a significant decrease in the heating enthalpy associated with the martensite-to-austenite transition after clinical use. The heating endsets (austenite finish temperatures) of the 27°C and 35°C wires were within 2°C of those claimed by the manufacturer, but the 40°C wires were found to be nearer to 36°C than 40°C. Conclusions: Clinical use of CuNiTi wires resulted in few differences when compared with as-received wires analyzed by DSC. Two temperature varieties of CuNiTi are reasonably within the parameters of those identified by the manufacturer

Relative Efficiencies and Design Charts for Various Engine-Propeller Combinations, Special Report

The relative efficiencies of various engine-propeller combinations were the subject of a study that covered the important flight conditions, particularly the take-off. Design charts that graphically correlate the various propeller parameters were prepared to facilitate the solution of problems and also to c1arify the conception of the relationships of the various engine-propeller design factors. It is shown that, among the many methods for improving the take-off thrust, the use of high-pitch, large-diameter controllable propellers turning at low rotational speeds is probably the most generally promising. With such a combination the take-off thrust may be further increased, at the expense of a small loss in cruising efficiency, by compromise designs wherein the pitch setting is slightly reduced and the diameter is further increased. The degree of compromise necessary to accomplish the maximum possible take-off improvement depends on such design factors as overspeeding and overboosting at take-off as well as depending on the design altitude. Both overspeeding and designing for altitude operation have the same effect on the take-off thrust as compromising in that the propulsive efficiency is increased thereby; boosting the engine, however, has the reverse effect on the propulsive efficiency, although the brake horsepower is increased

A study of the factors affecting the range of airplanes

A study was made of the most important factors affecting the range of airplanes. Numerical examples are given showing the effects of different variables on the range of a two-engine airplane. The takeoff problems of long-range airplanes are analyzed

Wind-tunnel Tests of Eight-blade Single and Dual-rotating Propellers in the Tractor Position

Tests of 10-ft. diameter, eight-blade, single - and dual - rotating propellers were conducted in 20-ft propeller research tunnel. Propellers were mounted at front end of a streamline body in spinners that covered hubs and parts of shanks. Effect of a symmetrical wing mounted in slipstream was investigated. Blade-angle settings ranged from 20 Degrees to 65 Degrees. Results indicated that dual rotation resulted in gains of from 1 to 8 percent in efficiency over single rotation for eight-blade propellers, but presence of a wing reduced gain about one-half. Greater power absorption caused by dual rotation over flight range and higher efficiency or thrust for range of take-off and climb was indicate

Preliminary Model Tests of a Wing-Duct Cooling System for Radial Engines, Special Report

Wind-tunnel tests were conducted on a model wing-nacelle combination to determine the practicability of cooling radial engines by forcing the cooling air into wing-duct entrances located in the propeller slipstream, passing the air through the engine baffles from rear to front, and ejecting the air through an annular slot near the front of the nacelle. The tests, which were of a preliminary nature, were made on a 5-foot-chord wing and a 20-inch-diameter nacelle. A 3-blade, 4-foot-diameter propeller was used. The tests indicated that this method of cooling and cowling radial engines is entirely practicable providing the wing of the prospective airplane is sufficiently thick to accommodate efficient entrance ducts , The drag of the cowlings tested was definitely less than for the conventional N.A.C.A. cowling, and the pressure available at low air speed corresponding to operation on the ground and at low flying speeds was apparently sufficient for cooling most present-day radial engines

The Torsional and Bending Deflection of Full-Scale Duralumin Propeller Blades under Normal Operating Conditions, Special Report

The torsional deflection of the blades of three full-scale duralumin propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10th of a degree was found at V/nD of 0.3 and a smaller deflection at higher values of V/nD for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading transit method used in the previous tests

Full-Scale Tests of 4- and 6-Blade, Single- and Dual-Rotating Propellers, Special Report

Test of 10-foot diameter, 4- and 6-blade single- and dual-rotating propellers were conducted in the 20-foot propeller-research tunnel. The propellers were mounted at the front end of a streamline body incorporating spinners to house the hub portions. The effect of a symmetrical wing mounted in the slipstream was investigated. The blade angles investigated ranged from 20 degrees to 65 degrees; the latter setting corresponds to airplane speeds of over 500 miles per hour. The results indicate that dual-rotating propellers were from 0 to 6% more efficient than single-rotating ones; but when operating in the presence of a wing the gain was reduced about one-half. Other advantages of dual-rotating propellers were found to include greater power absorption and greater efficiency at the low V/nD operating range of high pitch propellers

Wind-Tunnel Investigation of Rectangular Air-Duct Entrances in the Leading Edge of an NACA 23018 Wing, Special Report

A preliminary investigation of a number of duct entrances of rectangular shape installed in the leading edge of a wing was conducted in the NACA 20-foot tunnel to determine the external drag, the available pressure, the critical Mach numbers, and the effect on the maximum lift. The results showed that the most satisfactory entrances, which had practically no effect on the wing characteristics, had their lips approximately in the vertical plane of the leading edge of the wing. This requirement necessitated extending the lips outside the wing contour for all except the small entrances. Full dynamic pressure was found to be available over a fairly wide range of angle of attack. The critical Mach number for a small entrance was calculated to be as high as that for the plain wing but was slightly lower for the larger entrances tested

Preliminary Tests of Nose- and Side- Entrance Blower Cooling Systems for Radial Engines, Special Report

Two cowling systems intended to reduce the drag and improve the low-speed cooling characteristics of conventional radial engine cowlings were tested in model form to determine the practicability of the methods. One cowling included a blower mounted on the rear face of a large propeller spinner which drew cooling air in through side entrance ducts located behind the equivalent engine orifice plate. The air was passed through the equivalent engine orifice plate from rear to front and out through a slot between the spinner and the engine plate. The blower produced substantially all the power necessary to circulate the cooling air in some cases, so the quantity of air flowing was independent of the air speed, Two types of blowers were used, a centrifugal type and one using airfoil blades which forced the air outward from the center of rotation. The other cowling was similar to the conventional N.A.C.A. cowling except for the addition of a large propeller spinner nose. The spinner was provided with a hole in the nose to admit cooling air and blower blades to increase the pressure for cooling at low speeds. The tests show that with both cowling types the basic drag of the nacelle was reduced substantially below that for the N.A.C.A. cowling by virtue of the better nose shape made possible by the spinner . The drag due to the side-entrance ducts was nearly zero when the openings were closed or when the blower was drawing in a certain quantity of air in proportion to the air speed. The drag increased, however, when air mas allowed to spill from the openings. The nose-entrance blower showed considerable promise as a cooling means although the blower tested was relatively inefficient, owing to the fact that the blower compartments evidently were expanded too rapidly under the conditions imposed. by the design

Preliminary Tests of Blowers of Three Designs Operating in Conjunction with a Wing-Duct Cooling System for Radial Engines, Special Report

This paper is one of several dealing with methods intended to reduce the drag of present-day radial engine installations and improve the cooling at zero and low air speeds, The present paper describes model wind-tunnel tests of blowers of three designs tested in conjunction with a wing-nacelle combination. The principle of operation involved consists of drawing cooling air into ducts located in the wing root at the point of maximum slipstream velocity, passing the air through the engine baffles from rear to front, and exhausting the air through an annular slot located between the propeller and the engine with the aid of a blower mounted on the spinner. The test apparatus consisted essentially of a stub wing having a 5-foot chord and a 15-foot span, an engine nacelle of 20 inches diameter enclosing a 25-horsepower electric motor, and three blowers mounted on propeller spinners. Two of the blowers utilize centrifugal force while the other uses the lift from airfoils to force the air out radially through the exit slot. Maximum efficiencies of over 70 percent were obtained for the system as a whole. Pressures were measured over the entire flight range which were in excess of those necessary to cool present-day engines, The results indicated that blowers mounted on propeller spinners could be built sufficiently powerful and efficient to warrant their use as the only, or chief, means of forcing air through the cooling system, so that cooling would be independent of the speed of the airplane