Shaft Location Research Articles

On the shaft locations of two contra-rotating counterweights for balancing spatial mechanisms

It has been shown in a previous work that a frequency term of the shaking force of spatial mechanisms, whose hodograph is proved to be an ellipse, can be eliminated by a pair of contrarotating counterweights. In this work, it is found that the relevant frequency term of the shaking moment is minimized if the balancing shafts are coaxial at the centre of a family of ellipsoids, called isomomental ellipsoids, with respect to (w.r.t.) any point on an ellipsoid, as is also the root mean square (r.m.s.) of the relevant frequency term of the shaking moment. It can also be minimized even though the location of either shaft, but not both, is chosen arbitrarily on a plane. The location of the second shaft is then determinate. In order to locate the centre, a derivation for the theory of isomomental ellipsoids of a frequency term of the shaking moment of spatial mechanisms is given. It is shown that the r.m.s. of a frequency term shaking moment of a spatial mechanism w.r.t. the concentric centre of the isomomental ellipsoids is the minimum. Examples of a seven-link 7-R spatial linkage and a spatial slider-crank mechanism are included.

From the RSNA refresher courses. Freehand interventional sonography in the breast: basic principles and clinical applications.

The skills needed to perform ultrasonographic (US)-guided interventional procedures in the breast can be learned by practicing the key maneuvers on a tissue phantom. Use of a tissue phantom rather than a synthetic phantom provides the tactile feedback from transducer movement against tissue and from needle insertion into tissue, which more closely simulates the performance of the procedure in a real breast. There are three key transducer motions--sweeping, rocking, and rotating--that are used to achieve three important goals in US-guided procedures: finding the needle, maximally visualizing the needle, and correctly aligning the needle shaft and ultrasound beam. For each transducer maneuver, there is a corollary needle motion that can be used to achieve the same goal. Either the transducer or the needle should be moved during a procedure, not both simultaneously. Longitudinal alignment of the needle shaft with the ultrasound beam is best achieved with the perpendicular approach. The perpendicular approach is preferred because it allows superior needle visualization, orientation parallel to the chest wall, and location of the needle shaft at the focal zone. With use of a tissue phantom, the radiologist-in-training can practice the key procedures and tailor them to his or her individual preferences.

The ideal shaft locations of three-rotating-mass balancers for spatial mechanisms

The k th frequency term of the shaking force of high speed spatial mechanisms can be represented by three rotating force vectors of constant, but generally unequal, magnitude rotating on three mutually perpendicular planes at k times cycle frequency. The forces can be eliminated by equal and opposite forces exerted by counterweights mounted on the shafts rotating at the same speed. However, if the locations of these shafts are all arbitrarily chosen, the k th frequency term of the shaking couple will generally remain unbalanced. The equivalent system of the moment as well as the force components enables suitable shaft locations to be determined in such a way that this couple vanishes. The couple can be eliminated even though the location of one shaft among three is chosen arbitrarily, the locations of the other two shafts are then determined. An example of a 7 link 7-R spatial linkage is given to demonstrate the theory and the balancing effects of the three-rotating-mass balancers.

Application of sedimentology to the development and extraction of deep-mined coal

Abstract Most deep-mined coal in the UK comes from the Westphalian A and B (Langsettian-Duckmantian) of the coalfields of the Pennine Basin, in which several sedimentary facies have been identified. Deep mining of coal may be divided into four main operations: shaft sinking and driving of access drifts; drivage of underground roadways; excavation of coal faces; and the provision of temporary underground storage. The prediction of the lithological, geometrical and geotechnical properties of the various sedimentary facies likely to be encountered during mining is important for the success of all these operations. Roadway location may be influenced by the geotechnical attributes of the sedimentary facies, which also govern the type of machinery and methods used to cut and support the roads. The thickness, quality and continuity of the coal, and the properties of the roof and floor, are important in selecting the location of longwall faces and in their productivity. Facies composed of strong sedimentary rocks are likely to be the most suitable for the location of staple shafts and bunkers for coal storage. The geotechnical properties of each of the sedimentary facies is described, with particular reference to their excavation and support characteristics, and the discontinuities of sedimentary origin that are likely to be present. Distal lacustrine delta facies appear to provide the optimum roof conditions for coal faces and roadways. A simple scheme for the prediction of the sedimentary facies which may influence mining is presented, and a variety of mapping techniques, including facies maps, isopach maps and palaeocurrent analysis, are outlined. An improved knowledge of the properties and distribution of the various sedimentary facies at a mine site should lead to improved productivity and a reduction in risks and costs.

Prediction of engineering properties of a selected litharenite sandstone from its petrographic characteristics using correlation and multivariate statistical techniques

The determination of rock strength and elastic parameters in laboratory tests requires high quality core samples which are not always available from fractured and/or weathered strata. The purpose of this study is to apply a correlation analysis in conjunction with multivariate statistical techniques to petrographical and laboratory geomechanical data for the investigation of correlations that exist between these properties of a selected sandstone, and to suggest inexpensive predictive models in a preliminary investigation. Sandstone samples from a borehole drilled for a preliminary investigation of a shaft location at a hard coal region (Black Sea, Turkey) were tested to determine uniaxial compressive strength, elastic parameters, unit weight, porosity, point load index and quality index. Secondly, fifteen selected samples were subjected to petrographic examination which included fifteen parameters and modal analysis. Based on the statistical analysis results, polynomial prediction equations were developed for estimating mechanical properties from petrographic characteristics and index properties. The study revealed that the influence of textural characteristics appear to be more important than mineralogy for predicting engineering properties. It is also noted that type of contacts, grain shape and size, rock fragments with packing density and proximity are the petrographic characteristics which have significant influence upon engineering properties of the sandstones. Results of this study were presented in the form of correlation coefficient models and predictive models.

The Ideal Locations for the Contra-Rotating Shafts of Generalized Lanchester Balancers

The inertia of the moving parts of high-speed planar mechanisms creates a shaking force that is variable in magnitude, direction and line of action throughout a cycle. Alternatively, the instantaneous shaking force vector can be represented by an equal parallel force acting through an arbitrarily chosen origin, together with a moment about that origin. The two components of the force and the moment can be computed by kinetostatic analysis at discrete intervals of a cycle to create three arrays. The discrete Fourier transform converts these arrays from the time to the frequency domain. The lowest frequency term of order k = 1 is of cycle frequency. Terms of higher order k > 1 have frequencies that are k times cycle frequency. The shaking force frequency term of order k can be represented by two contra-rotating force vectors of constant, but generally unequal, magnitude rotating at k times cycle frequency. The forces can be eliminated by equal and opposite forces exerted by counterweights mounted on contra-rotating shafts rotating at the same speed. However, if the locations of these shafts are both arbitrarily chosen, a shaking couple of order k will generally remain unbalanced. Fast Fourier transform (FFT) analysis of the array of moments as well as the force components enables suitable shaft locations to be determined in such a way that this couple vanishes. The couple vanishes if the balancing shafts are coaxial with a centre at an invariant location in the plane. The couple can also be eliminated even though the location of either shaft, but not both, is chosen arbitrarily. The location of the second shaft is then determinate and two procedures are explained to determine that location.

Measured effect of step axial location on labyrinth seal leakage

An advanced, finite volume code has been extensively used in a parametric design study of simple stepped seals, in order to ascertain a leakage-minimizing optimal design and test it, in conjunction with the baseline case of the wear-ring seal of a high pressure pump. It is found that a significant leakage effect arises from this shifting of the rotor and stator sealing surfaces; at extremely low rpm, a significant shaft speed effect occurs for the optimized design in some shaft locations.

Measurement of torque in steam turbine-generator shafts following severe disturbances on the electrical supply system-analysis and implementation

Phenomena that affects the performance of transducers that measure torque at positions along a turbine-generator shaft are reviewed, and the design of a transducer for precise measurement of torque at positions on a steam turbine-generator shaft that results from severe disturbances of the electrical supply system is discussed. Torque at shaft couplings following severe supply system events predicted using continuum models of turbine-generator shafts are analyzed and compared with that obtained over a section of the shaft by shaft twist and overall stiffness of the section. Algorithms for processing torque deduced from twist over a section to estimate true torque at specific shaft locations are discussed. Studies are performed for severe L-L-L short circuits with clearance. The design of a transient shaft torque transducer which uses disks with slits which are secured to the rotating shaft is described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Intraoperative femoral fractures associated with cementless total hip arthroplasty.

Between 1982 and 1986, 56 femoral fractures associated with cementless total hip arthroplasty (THA) were evaluated and compared to a randomly selected cementless THA control group without fractures. Depending upon the femoral shaft location, these fractures were classified as Types I, II or III. There were 45 (80%) Type I, 9 (16%) Type II, and 2 (4%) Type III fractures. Patient evaluations were quantified using a modified d'Aubigne-Harris scoring system. Nonparametric statistical methodology was used for fracture and control group comparisons. Treatment protocols were divided into various modalities, depending upon fracture classification. Type I and Type II fractures have no long-term prognostic hazards associated with them (P greater than 0.1), while Type III fractures appear to have analogous clinical results (sample size was too small for statistical analysis).

886195 Land development. State-of-the-art in the location of old mine shafts : Bell, F G Int Assoc Engng Geol BullN37, April 1988, P91–98

886195 Land development. State-of-the-art in the location of old mine shafts : Bell, F G Int Assoc Engng Geol BullN37, April 1988, P91–98

Land development. State-of-the-art in the location of old mine shafts

Because mining has gone on in the United Kingdom for centuries there is a legacy of the shafts left behind, most of which are unrecorded. Where land is to be developed and the presence of an old shaft is suspected, the location of the shaft must be determined so that shaft can be dealt with. The primary reason for this is that an abandoned shaft may pose a potential danger. Frequently when shafts were abandoned they were inadequately filled or simply sealed over at the surface. Hence the possibility of shaft collapse exists or the land around a shaft may subside. If superficial deposits surround the shaft, collapse leads to the formation of a crater at the surface, the diameter of which is much larger than that of the shaft.

Effect of Fault Clearing and Damper Modelling on Excitation and Decay of Vibrations in Generator Shafts Following Severe Disturbances on the System Supply

The paper examines the effect damper circuit modelling and the current interruption process has on amplitude and decay of torsional vibrations in turbine-generator shafts following severe supply network disturbances. A phase-variable model of a synchronous-generator with up to 2 direct-axis and 3 quadrature-axis dampers where fault current is cleared at fault current zeros is employed to calculate generator airgap torque which results from a severe disturbance on the electrical supply. Using airgap torque, effective amplitude of torque excitation acting on the generator rotor for each eigenfrequency is determined by Fourier analysis. Amplitude of torsional vibration at each shaft section for each modal frequency is then calculated. Shaft torque at each shaft location for each modal frequency is thereby deduced. These components, together with the steady-state component (and that due to rotor swing), are summed as absolute values for all modal frequencies to yield approximate peak torque at critical locations along the shaft following each disturbance. Approximate peak shaft torque estimated by frequency domain analysis is compared in some instances with peak torque predicted by solution of exact differential equations. Presented results illustrate amplitude of torque excitation and shaft torques as a function of fault clearing time for L-L-L and L-L high-voltage system short-circuits, and effect reactive power and system resistance has on damping predominant torsional vibrations in the shaft.

Shaft design criteria

Criteria for shaft design are described and methods of design developed. Among aspects covered in detail are: selection of shaft locations; shaft collar design and determination of collar dimensions; shaft lining design and estimation of side pressures; shaft insets and sump design. Factors considered, apart from geotechnical criteria include constraints imposed by surface structures, mineral handling and water flows.

The synthesis of fracture/strength logs using borehole geophysics: a new geotechnical service

Summary In the coal industry, the present energy situation and economic climate have increased the need for rapidly acquired, cost effective, reliable assessment of the strengths of rock which may be encountered in shafts, drifts and access tunnels, this need having hitherto been met by conventional sampling and testing procedures. This paper describes a new technique based on the processing of down-hole geophysical logs to provide a continuous, accurate record of these properties speedily and at relatively low cost. The basis of the technique is to include a Neutron-Neutron log in the standard logging package and process it with the caliper log either to generate a Hydrogen Index log or simply a caliper compensated Neutron-Neutron log. The derived log is then split into selected lithology-dependent sub-groups and modified according to a predetermined set of calibration constants. These calibration constants have been determined by the authors for the Coal Measures of Staffordshire but can be readily re-determined, if necessary, to suit other coalfields or prospects as required. The application of the technique has the potential to improve all forms of engineering site investigation where both stability and ‘extractability’ of rock are under consideration, often removing the need to acquire expensive rock core samples, and saving considerable labour costs. In the U.K. coal mining industry fracture logs synthesized using this technique are at present being supplied, so that their value, in the planning and location of shafts and tunnels, in the design of shaft insets and tunnel supports, in the selection of tunnelling machines and forecasting drivage rates and in predicting roof, floor and overburden characteristics may be assessed. It is believed that they will have applications in many other mining or site investigation environments. The technique described in this paper is the subject of a patent filed by N.C.B. Patents Ltd.

Stressing of Large Turbine-Generators at Shaft Couplings and LP Turbine Final-Stage Blade Roots Following Clearance of Grid System Faults and Faulty Synchronisation

The paper examines transient torque phenomena which can arise at LP turbine blade roots and at shaft couplings of large synchronous-generators following a grid network disturbance. Fault clearance and faulty synchronisations for two 3000 rpm 660 MW turbines and a 3600 rpm, 300 MW turbine is examined. Peak torque at various shaft locations and at the LP turbine final-stage blade roots is computed as a function of the fault clearing time or the synchronising angle respectively. Stresses induced at LP turbine blade roots where the shaft system is protected against excessive stress by use of a turbine/generator shearing coupling is examined for one turbine only. Sustained 3-phase and line-to-line faults at the generator stator terminals are also considered.

Sampling and In-Situ Density of a Saturated Gravel Deposit

Abstract Attempts to sample a saturated gravel deposit beneath a proposed nuclear power plant with standard drilling methods and sampling techniques were unsuccessful. To provide the necessary information on in-situ stratigraphy and density, an alternate exploratory method and sampling technique was designed. In this method, a 107-cm (42-in.) uncased shaft was drilled to a depth of 14.3 m (47 ft) after freezing the soil around the shaft location. The soil stratigraphy, composition, and structure in the uncased shaft were then exposed in great detail for mapping and photographing. Two frozen undisturbed samples were cut from the walls of the shaft in loose gravel layer and the in-situ density was determined using a fluid displacement technique. Maximum and minimum densities were obtained for the thawed soil for calculation of in-situ relative density. Standard Penetration Test (ASTM D 1586, Penetration Test and Split-Barrel Sampling of Soils) results successfully indicated the approximate location and thickness of the loose layer despite the sampling difficulties and high gravel content. Judging from inch-by-inch blow count data, the high gravel content increased the penetration resistance values (through the spoon pushing a large gravel piece) in only a small number of samples.

Location of old mine shafts by a geoelectric method (in Polish) : Podio, R Przegl Gorn, V34, N7–8, July–August 1978, .

Location of old mine shafts by a geoelectric method (in Polish) : Podio, R Przegl Gorn, V34, N7–8, July–August 1978, .

A Study of the Lubrication and Dynamics of Geometrically Perfect, Lightly Loaded, Cylindrical Roller Bearings with Particular Reference to Shaft Loci

The principal objective of this paper is to ascertain and quantify the cyclic movement of the centre of a shaft in a geometrically perfect, lubricated, cylindrical roller bearing exhibiting initial clearance and subjected to a light and steady load. The movement may be important in relation to the accuracy of location of shafts in roller bearings, and it is shown that a detailed consideration of the rolling element assembly predicts some interesting effects. The study also covers more conventional features of bearing performance such as lubricant film thickness and coefficient of friction, and shows the effect of squeeze to be negligible under steady bearing loads.

Depth location of shafts filling half the space between Mueller-Lyer fins.

Using luminous stimuli in a dark room, Ss were required to judge the apparent depth location of shafts filling half the space between the ingoing and outgoing fins of the Mueller-Lyer illusion. Under these conditions there is a reversal of the apparent depth location of the shafts as compared with the usual M-L illusion. This finding is contrary to a prediction derived from the misapplied size-constancy theory but can be interpreted in terms of the size-distance principle.

Effect of Eccentric Shaft Location on the Dynamic Performance of the Propeller of a Single-Screw Tanker

In this experimental research the effect of an eccentric shaft location on the propeller-excited vibratory forces in the propeller shaft has been investigated for a single-screw 32, 000-dwt tanker with a block coefficient of 0.769. Tests were carried out for a four and for a five-bladed propeller with conventional shaft location, as well as with a set-off of the propeller shaft of 5 and 10 percent of the propeller diameter, respectively.