Simple Gear Research Articles

A Lightweight Split-Torque Transmission for a 330 KW Helicopter

A simple split-torque gear train is used as the main rotor transmission of a single-engine helicopter. Overall speed reduction ratio achieved is 103:1 between the engine at a nominal 36 000 rev/min and the main rotor at 350 rev/min. This ratio is generated from three stages of fixed-axis gear trains containing only eight gears. Alternative configurations are outlined and discussed. Comparison with a current production design shows the split torque arrangement offers reductions in weight, height, and drive train losses. A low total of gears and bearings offers the potential for improved reliability.

A multielement magnetic gear

The paper presents an appraisal of the problems inherent in the production of a magnetic gear. A new form of gear is presented, together with the theoretical basis of its operation, and is compared with a simple wheel gear. Experimental results are included for a complete gear and for the constructional elements.

A problem of astronomical proportion

It is easy to design simple gearing enabling a clock or instrument to indicate hours, minutes and seconds, since the ratios are ‘man-made’ integers. If an instrument is required to indicate astronomical data we find that nature is not so considerate, and the gearing presents an interesting problem.

Conditions for the Neutralization of Excitation by the Teeth in Epicyclic Gearing

Excitation of vibration by the teeth in a simple epicyclic gear system is considered, and it is shown that some of the potentially troublesome harmonic components can be neutralized by suitable choice of tooth numbers. In particular, the tooth frequency components acting on the central members are found to be neutralized if the number of teeth on the sun divided by the number of planets ( ZS/n) ≠ integer and ( ZS ± 1)/ n ≠ integer, provided that one of the central members is fixed. The practicability of satisfying the conditions and factors which tend to reduce their effectiveness are discussed.

Contribution to the geometry of elliptic gears

It is shown that the motion of elliptic wheels, usually derived from the antiparallelogram, can be constrained by a crossed transmission belt which is wound around two equal elliptic disks, confocal with the rolling ellipses. By considering the relative paths of belt points, one arrives at a simple gearing system for wheels of this kind which is the natural generalization of the usual involute system for circular wheels.

Three-speed single-winding squirrel-cage induction motors

A 2-speed single-winding squirrel-cage induction motor, with only six terminals and of excellent rating and performance, has been described in several previous papers. The same principles have now been extended to give a 3-speed motor of comparable quality. Only twelve terminals and reasonably simple control gear are required for three speeds. Almost any speed combination can be obtained, the example given in the paper being a motor for 6/8/10 poles, particularly suitable for fan or pump drives.

Instrumentation for a Consolidation Study of a Clay Deposit Beneath an Embankment

Synopsis In order to instrument a deep clay deposit for measurements of consolidation beneath a 23-ft-high embankment, it was necessary to develop a settlement gauge which could be installed just below the natural ground surface before the embankment was constructed. The Paper presents the considerations involved in the design of such a gauge and describes the one finally adopted. Measurements of settlements between the natural ground surface and reference elevations within the clay deposit are made by determining electrical resistances which are proportional to vertical displacements. This is accomplished by the simple gearing of a chain and sprocket to the shaft of a spirally wound potentiometer. By a judicious choice of potentiometer and sprocket pitch diameter it is possible to determine displacements to an accuracy of 0·05 in or 1·3 mm. The field installation is described in detail and, finally, time-settlement curves for four gauges are shown. Afin de mesurer scientifiquement le tassement d'un profond dépôt d'argile situé sous un remblai mesurant 23 pieds de haut il a fallu concevoir une jauge spéciale qu'on pourrait installer sous la surface du terrain naturel avant de faire le remblai. On passe en revue les considérations dont on a term compte dans la mise au point de ce type d'instrument et on décrit la jauge qu'on a finalement adoptée. La mesure des tassements produits entre la surface du sol naturel et les points de référence choisis à différentes hauteurs dans le dépôt s'est effectuée en déterminant les résistances électriques lesquelles sont proportionnelles aux déplacements verticaux. On a réalisé cette mesure en engrenant simplement une galle à l'axe d'un potentiomêtre hélicoïde. En choisissant comme il faut le diamètre du pas on a pu déterminer les déplacements à 0·05 pouce ou 1·3 mm près. L'installation utilisée pour la mesure est décrite en détails et l'étude est complétée par des courbes de tassement établies en fonction du temps.

A Note on the Vibration of Systems Containing Epicyclic Gears

The Purpose of this note is to present a table of the receptances of simple epicyclic gears and to show how they may be used. This table of results has two main uses. In the first place the receptances simplify the calculation of the natural frequencies of torsional systems containing these gears by the methods explained previously. Secondly, responses of systems (which incorporate these gears) to given harmonic excitations may be estimated, either in the absence of damping, or when there is damping present of known amount in the component sub-systems. This second use of receptances is illustrated by a simple example in this note; it is based upon the fact that the receptances of a compound system may be built up from those of its sub-systems irrespective of whether there is damping present or not.

Wider Application of the Electrical Method of Collecting Fish

Limitations of the electrical-shock method of collecting fish, as commonly used, are reviewed. Among these are the facts that the equipment considered necessary is cumbersome and costly; that the method is effective only on quite narrow, clear-water streams; that effectiveness varies greatly with chemical content of soil and water; and that it is dangerous. Equipment and techniques that overcome these limitations to a greater or lesser extent are described. It has been found that less and more simple gear can be used effectively and safely. Methods of handling equipment which eliminate many time-consuming delays have been developed. Equipment and procedures which are fully satisfactory on wider streams and in turbid waters are described. An electric “seine,” effective in streams 90 to 100 feet wide, has been developed. By employing special techniques, it can be used quite effectively in wider streams. In turbid water the method is less efficient but quite satisfactory sampling of the fish population can be made. Preliminary experiments have been made on the amount of electric current needed to stun fish without killing them. Apparently, most species of fish will be stunned but will recover in a few minutes from shock caused by 5 to 6 amperes of alternating current at 110 volts. Larger fish seem to be stunned more readily than those of fingerling size. Experiments on the efficiency of the method have been started. Factors influencing efficiency are believed to be chiefly those related to the recovery of stunned fish. Turbid water, swift current, and rough bottom all seem to decrease efficiency. Experimental evidence to confirm these beliefs is incomplete and inconclusive but it is evident that the method is highly effective in sampling qualitatively areas which otherwise could not be worked.

Single‐Stage Superchargers

IN many types of engine the supercharger is built on to the accessory‐drive end, that is the rear of the engine, so that the supercharger shaft lies co‐axially or parallel with the crankshaft. This has the great advantage of permitting the use of simple spur gearing, but suffers from the disadvantage that in passing through both intake and delivery section, the working fluid is subjected to several right‐angled changes in direction. In the case of the Rolls‐Royce Merlin for example, with air intakes on either side, there are 2 × 2 right‐angled bends before the inlet to the impellor is reached and two more at the delivery side. Such bends naturally involve losses in supercharging which should definitely be avoided. Hence in Germany in the two liquid‐cooled inline types the Jumo 211 (Fig. 1) and Mercedes‐Benz DB600 (Fig. 2) the supercharger shaft is built square to the engine crankshaft and the supercharger located at the side of the transmission casing, so that a single right‐angled bend suffices to change the direction of flow of intake air from that of flight and lead it axially to the impellor. If, at the same time, care is taken in nacelle design to ensure an undisturbed flow of air to the intake duct, then the total static head of flight may be utilized in supercharging the engine, resulting in an increased altitude rating. The proportion of this increase due to full utilization of the flight static head is shown in Fig. 3. For example, at a speed of 600 km.p.h. (373 m.p.h.) its value is about 1,400 m. (4,600 ft.)

A simple reduction gear and clutch

A simple reduction gear and clutch

Societies and Academies

PARIS. Academy of Sciences, August 4.—M. Leon Guignard in the chair.—G. Humbert: The formation of a fundamental domain of an automorph group.— P. Marchal: The evolutive cycle of the woolly Aphis of the apple-tree (Eriosoma lanigera). It has been proved that in America the American elm harbours the sexual generation of American blight, whilst the apple and some other trees of the same group act as intermediate hosts. In Europe the cycle would appear to be different; the sexual generation does not occur, and the species is continued during the winter by hibernation on the apple-tree, the reproduction being parthenogenetic.—E. Ariès: The density of the saturated vapour of propyl acetate and the density of the liquid emitting this vapour.—A. Denjoy: Riemannian integration.—N. E. Nörlund: The polynomials of Euler.—R. Gamier: The irregular singularities of linear differential equations.—E. Kogbet-Hantz: The integral of Angelesco.—C. Frémont: New methods for the mechanical testing of metals. Description and diagrams of two simple pieces of apparatus for measuring the tensile strength and resistance to shock of metal test-pieces of very small dimensions.—E. Esclangon: The mechanical transformation of sidereal time into mean time. Calculations of simple gears show that with four wheels having 119, 330, 317, and 314 teeth the conversion can be made with the loss of only one second hi eight years; with wheels having 188, 465, 563, and 227 teeth the error can be reduced ito one second in 249 years.—P. Roubertie and A. Nemirovsky: Some new fluorescent screens for use in radioscopy. As a substitute for platinocyanides in radioscopic screens, cadmium tungstate has given good results. This material forms screens which are stable in air, and unaffected by prolonged exposure to X-rays. —R. Levaillant and L. J. Simon: The action of chloro-sulphonic acid on methyl sulphate. The preparation of methyl ehlorosuiphonate.—G. Mignonac: The synthesis of ketiminesi by the catalytic method. A mixture of ammonia and the vapour of a ketone passed over thoria at 3oo°–4oo° gives a ketimine of the type R.C(N,H).R′. The method fails with fatty ketones, condensation products of the ketimines being produced. The preparation and properties of methylphenyl-, ethylphenyl-, cyclohexyl-, and diphenyl-ketimines are described.—L. Daniel and M. Thoulet: Shell deposits in the neighbourhood of Erquy (Côtes-du-Nord).—H. Conpin: The absorption of mineral salts by the root-tip. The root-tip can absorb mineral salts in solution, and these are freely utilised by the growing plant.—P. Vayssiere: Some methods for the destruction of crickets and their application. Trials were made of flame projectors, poison gas, and arsenical pastes, and all of these can be used with success under certain conditions. Sprays of chloro-picrin (50 per cent.) can be used where a flame is inadvisable, and arsenical pastes in places where there are no animals at pasture. Special organisations under direct State control will be necessary if these measures are to be carried out effectively.—H. Violle: The peroxydases in milk. The peroxydase reaction cannot be used to judge the quality of a milk; normal milk from o a healthy cow may contain very little peroxydase, whilst milk from a diseased udder may contain peroxydase in quantity.—W. Kopaczevski and A. Vahram: The suppression of anaphylactic shock. The injection of solutions of sodium oleate, sodium taurocholaite, sodium glycocholate, or of saponin five minutes before the second injection of serum completely suppresses the anaphylactic shock in guinea-pigs.—J. Amar: The elastic force of diseased lungs.–V. Galippe: New researches on the presence of living organisms in the cells of the male genital glands (microbiosis, normal or accidental parasitism).