Spring Height Research Articles

Natural Frequency Study of Automotive Engine Valve Spring by Experimental Method

This paper presents a frequency response function method to measure the natural frequency of automotive engine valve springs with respect to different spring height. A new apparatus is developed for changing the spring height within the range of valve lift. The test results indicate that the natural frequency changing highly depends on the different pitch type of the spring. The measured natural frequencies of valve spring can be direct applied to the estimation of valve spring surge characteristics.

Development and analysis of an air spring model

The analytical model of an air spring can be effectively used for the design of air spring equipped vehicles to provide better ride and handling characteristics along with various functions for passenger convenience. However, establishing a general model of an air spring poses particular difficulties due to the severe nonlinearities in the stiffness and the hysteresis effects, which are hardly observed in conventional coil springs. The purpose of this study is to develop a general analytic model of an air spring — one which represents the main characteristics of stiffness and hysteresis and which can be connected to a model of pneumatic systems desigined to control air spring height. To this end, the mathematical model was established on the basis of thermodynamics with the assumptions that the thermodynamic parameters do not vary with the position inside the air spring, that the air has the ideal gas property, and that the kinetic and potential energies of the air are negligible. The analysis of the model has revealed that the stiffness is affected by the volume variation, the heat transfer, and the variation of the air mass and the effective area. However, the hysteresis is mainly affected by the heat transfer and the variation of the effective area. In particular, it was revealed that the increase of the volume due to the cross-sectional area increases the stiffness, while the increase of the volume due to the other reason decreases it. In addition, the model was used to develop the sufficient stability condition, and the stability of the model was analyzed. The paper also presents the comparison between the simulation and experimental results to validate the established model and demonstrates the potential of the model to be usefully employed for the development of the air spring and its algorithm for use in a pneumatic system.

Low-frequency two-dimensional resonators for vibrational micro energy harvesting

The fabrication, characterization and theoretical analysis of a novel two-dimensional silicon resonator with threefold rotational symmetry are described. The resonator consists of a 4 mm wide disk-shaped seismic mass having the full-wafer thickness of 525 µm and suspended by a system of concentric circular springs. The device is structured using two-sided deep reactive-ion etching of silicon. With its current spring thickness and height, the device has two closely spaced resonance frequencies at 370.5 and 373.9 Hz and a quality factor of 1800 at ambient pressure. The spring height and thus the resonance frequency of the device are easily tuned by simple adjustment of a single etch duration in the entire fabrication process. The dynamic response of the structure is modeled under the two assumptions that silicon is elastically (i) isotropic and (ii) anisotropic. In comparison with the isotropic model, the elastic anisotropy leads to a predicted mode splitting by 6.2 Hz, with oscillation directions aligned with the cubic crystal axes. Even small geometrical imperfections are found to significantly rotate the eigenmodes and to further modulate their frequency splitting. Experimental and numerical results corroborate these conclusions. Overall the present resonator design has the potential for a higher energy harvesting efficiency than a combination of two separate one-dimensional oscillators.

A Control Method for Hybrid Tilting Systems using Tilting Beams and Air Spring Inclination

To further increase the speed of railway vehicles running on existing narrow-gauge track, we developed a new tilting system that enables the car body to tilt at a larger angle than conventional tilting trains. The system coordinates tilting beams and a controlled air spring height, thus reducing losses in wheel-load and avoiding lateral displacement of the car body caused by the larger tilting angle. This paper reports the features of the hybrid tilting system, the control method applicable to such tilting and the results of the bench tests carried out.

On the New Air Spring Control System for Railway Vehicles.

A new air supply / exhaust control system was developed for pneumatic suspension of railway vehicle. This system which equalizes unbalanced inner pressure of air spring and horizontalizes the vehicle floor when the vehicle is slowed or stopped. It counters such defects experienced in the conventional leveling valve (LV) system as large unbalance of air spring inner pressure when stopping at distorted track of transient curve that might cause wheel unloading and decrease the derailment safety margin. The new control system is composed of solenoid valves, height and pressure sensors, clinometer and controller (CPU). Major control laws are (1) detect forced deflection of air spring caused by track distortion, (2) equalize the air spring height distortion when running, (3) horizontalize vehicle when slowed or stopped, and (4) equalize air spring pressure unbalance. These functions are implemented in a computer program.

A parametric study of the force/moment systems produced by T-loop retraction springs

This study considers the effects of several parameters on the force/moment systems produced by T-loop retraction springs. The springs are studied by using the finite element method and by experimentally measuring the forces and moments from the various designs. The results show that varying the spring height can produce larger moment to force ratios as the height increases. Changes in the preactivation bends result in unsymmetric moment characteristics and also produce large intrusive/extrusive forces. The addition of helices at the bends did little to alter the springs' mechanical characteristics.

Optimizing anterior and canine retraction

Vertical loops or modified vertical loops are basically frictionless springs which are used for canine and anterior tooth retraction. The design and selection of a proper loop or retraction spring should be based on a number of scientific criteria. Foremost among these would be a sufficiently high moment-to-force ratio so that root apices are not displaced mesially or anteriorly. A retraction spring with zero angulation of its horizontal-occlusal arms delivers a moment when activated to produce a force. The ratio of this moment and force is constant throughout the elastic range of activation of the spring. The higher the moment-to-force ratio, the greater is the clinician's control over the apices of the anterior teeth. An analysis of design factors demonstrates that the higher the loop occluso-gingivally, the shorter its horizontal length occlusally, and the greater the gingival horizontal length as in a T loop; these are significant factors in increasing the moment-to-force ratio. The placement of helices is a useful design consideration but the main effect is in reducing the load-deflection rate. By keeping these design factors in mind, the clinician can build into his retraction springs, without the placement of any gable bend, the largest possible moment-to-force ratio so as to optimize his tooth movement. Although it may be possible to design retraction springs to deliver an adequate moment-to-force ratio for controlled tipping around the apex of an incisor or a canine, translatory movements are not possible, considering the intraoral limitations on spring height. This can be overcome by the placement of gable bends or angulation in a vertical loop or retraction spring. Unfortunately, with the typically used high-load-deflection-rate vertical loops, activation to achieve the desired moment-to-force ratio is too critical, exacting, and changeable with small displaced movements of the tooth. This can be partly overcome by utilizing designs that have not only the highest possible moment-to-force ratio during pure horizontal activation of their arms but low-load deflection rates as well. Because of the low load-deflection rate, moment-to-force ratios are relatively more constant if a gable bend (angulation) is placed. The science of spring design as applied to the problems of canine and anterior tooth retraction in this article allows the clinician to optimize the design of his retraction springs. More important, with properly designed springs, it allows him to estimate with relative accuracy the force systems produced and to avoid undesirable side effects which might not have been apparent from superficial observation.

Relationship Among Seedling Height, Greenhouse Regrowth, Fall Height, and Spring Height in Medicago sativa L.1

Crosses of early fall dormant ✕ early fall dormant,early dormant ✕ late dormant, and late dormant ✕ late dormant clones of Medicago sativa L. were planted in greenhouse flats and subsequently transplanted into the field. Seedling height, greenhouse regrowth, fall height (regrowth), spring height (regrowth), and percent winterkill were recorded. Correlation coefficients indicated that 25 to 36% of the variation in greenhouse regrowth could be associated with seedling height. Less than 5% of the variation in fall height and spring height could be associated with seedling height. A similar relationship was noted between fall height and spring height. This relationship, along with the range of types found in any seedling class, suggested that plants with good seedling vigor and good spring recovery could be selected from the early dormant ✕ early dormant group even though the tallest plants for fall height were only about half as tall as those in the early ✕ early or late ✕ late group. The segregation in the early ✕ late and late ✕ late group suggested that winterhardy plants with good seedling vigor, good regrowth, having tall fall and spring height could be selected.

Some parasitic deflexions in parallel spring movements

This paper analyses some parasitic departures from parallel and rectilinear movement in simple and compound assemblies. The following factors are considered: accuracy of construction, geometrical proportions, spring variations, spring distortion, platform bending, clamp distortion, and gravity effects. It is shown that the ideal height at which to drive a parallel spring element is at half the spring height, and it is concluded that while spring tolerances are surprisingly easy, care must be taken with the platforms and clamps if the highest performances are to be achieved. In compound movements, the possibility of slaving the intermediate platform, suggested by Plainevaux, has been tested in practice with good results.

Tide researches. Fourteenth series. On the results of continued tide observations at several places on the British coasts

Tide observations made at several different parts of the British and neighbouring shores, and in some instances continued for a considerable period, having been discussed by Mr. D. Ross of the Hydrographer’s Office, with great labour and perseverance, a brief statement of the results which his labours afford is here presented by Dr. Whewell. The discussions here referred to relate to the height of high water, and the variations which this height undergoes in proceeding from springs to neaps, and from neaps to springs. It is found, by examining the observations at 120 places, and throwing the heights into curves, that the curve is very nearly of the same form at all these places. Hence the semi-mensual series of heights at any place affords a rule for the series of heights at all other places where the difference of spring height and neap height is the same. For instance, Portsmouth, where the difference of spring height and neap height is 2 ft. 8 in., is a rule for Cork, Waterford, Inverness, Bantry, Arcachan on the French coast, and other places: and the tables of the heights of high water at one of these places suffices for all the others, a constant being of course added or subtracted according to the position of the zero-point from which the heights at each place are measured.

XI. Researches on the tides.—fourteenth series. on the results of continued tide observations at several places on the british coasts

Tide observations made at several different parts of the British and the neighbouring shores, and in some instances continued for a considerable period, have been discussed by Mr. D. Ross of the Hydrographer’s Office, with great labour and perseverance; and as the results which his labours afford may be of use to mariners, I offer to the Royal Society a brief statement of these results. The discussions at present referred to relate to the height of high water, and the variations which this height undergoes in proceeding from springs to neaps and from neaps to springs. It is found, by examining the observations at 120 places and throwing the heights into curves, that the curve is very nearly of the same form at all these places. Hence the semimensual series of heights at any place affords a rule for the series of heights at all other places where the difference of spring height and neap height is the same. For instance, Portsmouth, where the difference of spring height and neap height is 2 feet 8 inches, is a rule for Cork, Waterford, Inverness, Bantry, Boucout on the French coast, and other places.