Belt Friction Research Articles

Force distribution for a flat belt drive with a concentrated contact load

An equation based on the classical Euler formula is derived to investigate the normal and tangential belt force distribution of a flat belt drive when a concentrated contact load is applied on the pulley. This loading condition occurs in an abrasive belt grinding. The belt force equation presented in this paper has a constant coefficient of friction. Analytical results show good agreement with the experimental results and the authors' previous work, which is based on a surface model of the belt friction face with a varying coefficient of friction. The equation developed from the Euler formula is suggested for practical design due to its sufficient accuracy and simplicity.

A new stretcher design for easy manoeuvreability on narrow staircases and rough ground for developing countries.

Rough terrains with obstacles, narrow staircases and inadequate space to position the ambulance conveniently in relation to the exit door of houses, often encountered in developing countries like India, make it difficult if not impossible to carry patients using conventional stretchers. A novel two-wheeled stretcher to overcome the limitations has been designed, fabricated and tested for a decade. The special features allow even one stretcher operator to transport a patient over all types of ground, down staircases with landings so small as not to provide space for a regular stretcher to turn into and out from the ambulance. This wide range of facilities has been obtained by incorporating very simple and low-cost devices such as a metal guard over two wheels, friction belts and an ergonomically designed tie bar system. Usage in handling various medical and surgical emergency cases has proven the efficacy and acceptability of the design.

Axial forces of a V-belt CVT

A simple analytical formula is derived for the axial forces of a V-belt CVT drive. For the driver pulley axial force, belt tension is assumed to be constant by self-locking. For the driven pulley axial force, the whole arc of contact between the belt and the pulley is divided into two regions; (1) inactive and (2) active area. The sliding angle o for the belt friction is approximated as o=0 in the active area. It is found that the results of the new formula are in close agreement with the exact solution. The new formula is suggested for the V-belt CVT design due to its simplicity and sufficient accuracy.

Toothed Belt-Load Distribution

A mathematical model was developed to study the effect on belt load distribution of belt material properties, pitch variations, friction force, and pulley rotation. Results are presented which show the influence on load distribution of pitch difference, tight side tension, slack side tension, belt tooth spring constant, and coefficient of friction, for the belt on stationary, driver, and driven pulleys. Data from the mathematical model compared well with experimental results available in the literature.

In-line Application of Porous Wax Coating Materials to Reduce Friction Discoloration of ‘Bartlett’ and ‘d’Anjou’ Pears1,2

Abstract ‘Bartlett’ and ‘d’Anjou’ pears (Pyrus communis L.) were passed through several brushrollers during washing, rinsing, waxing, and drying sequences of a simulated packing process. In-line application of Fresh-Cote, a wax coating formula with porosity, to the pear surface at waxing location of the packing line reduced peel discoloration of ‘Bartlett’, but not ‘d’Anjou’, due to brush friction. Fruits also were subjected to a return flow belt for 5 minutes to simulate the sorting sequence during packing. Fresh-Cote substantially reduced the susceptibility of both ‘Bartlett’ and ‘d’Anjou’ pears to peel discoloration due to belt friction.

Modification of the Monark bicycle ergometer for underwater exercise.

A standard Monark bicycle ergometer was modified for underwater exercise by removal of the friction belt and attachment of one to six metal fins to the flywheel. Three fins could be fastened to either side of the flywheel. The fins used on the left side of the wheel were made of standard perforated angle iron with the perpendicular side measuring 38 mm; those on the right side were made from the same length of nonperforated angle iron but with a perpendicular side of only 26 mm. Net surface area of the two types of fins (excluding area of perforation) was the same. Oxygen uptake (VO2) was found to be: VO2 = a(rpm)b + 0.25, 1.min-1, with a = 0.00164 -- 0.00104n + 0.000266n2 -- 0.00002n3; b = 1.64 + 0.506n -- 0.104n2 + 0.00667n3, when n is the number of fins. The correlation coefficient (r) between measured and predicted VO2 was r = 0.98. The preferable range of pedaling speeds was 29-40 rpm to maintain a constant speed for up to 1 h. Major advantages of this modified ergometer for underwater exercise are 1) the modification is simple and the same ergometer can be used for land exercise, 2) the ergometer can be biologically calibrated and used for a wide range of exercise oxygen uptakes, and 3) subjects can perform for a proportionally longer time period than other modifications of the same ergometer.

A Machine that Separates Rough from Smooth Seed

ABSTRACT Anew machine has been developed to separate con-taminants from seed by sensing differences in sur-face textures. A moving friction belt carries the seed mix-ture to intercepting pairs of bars that separate rough from smooth particles. The machine has effectively removed contaminants from 38 seed mixtures including dirt clods from beans, dodder from alfalfa, and inert material from many seeds.

Control systems for heavy multidrive conveyers

In heavy conveyer belts it is usual to take the optimum conditions of the friction pulleys and belt to be such as will effect equal, minimal reserves of tractive capacity in the driving drums. This can be achieved by redistributing the tractive forces between the drums and by regulating the tension in the belt by means of the instantaneous tractive force of the conveyer. To get optimum operation of the conveyer belt, the load on the conveyer bed must be equal to the nominal value; this can be achieved by means of an automatic dosing device in the loading unit of the conveyer with a receiving bunker of sufficient capacity, or by regulating the conveyer speed according to the load flow. A load control system must include the following subsystems: (1) an automatic dosing unit; and (2) control of the speed according to the load flow and the tension in the belt, starting with the required force. Under normal conditions only subsystem 1 operates (the conveyer speed and the tension in the belt are constant). Subsystem 2 is brought intoaction only when the fluctuations of the load flow are such that subsystem 1 cannot do its job. Speed regulation ofmore » a multidrive conveyer presents a number of problems concerning the regulation of the relations between the tractive forces of the driving drums and the tensions, and also the starting and stopping conditions. In practical conveyer design, one of the most promising measures to increase the lengths of monobar conveyers without altering their throughput is the use of distributed drives in the working branch, giving relatively uniform distribution of the tractive force among the parts of the traction unit. The theoretical principles of construction of control systems for multidrive conveyers with optimal technological parameters are given.« less

2798. A note on belt friction

2798. A note on belt friction

Ship waves: The relative efficiency of bow and stern

It seems fairly certain that one of the main causes of difference between theoretical and experimental results is the neglect of fluid friction in the calculation of ship wave, and further that the influence of fluid friction may be regarded chiefly as one which makes the rear portion of the ship less effective in generating wave than the front portion. The process may be pictured, possibly, in terms of a friction belt or boundary layer whose more important effect is equivalent to smoothing the lines of the model towards the rear. Some calculations were made from this point of view in a previous paper, the purpose then being to show how such an asymmetry, fore and aft, reduced the magnitude of interference effects between how and stern waves. We may also describe the frictional effect as a diminution in the effective relative velocity of the model and the surrounding water as we pass from how to stern. This is not very satisfactory from a theoretical point of view; but, on the other hand, it leads to a comparatively simple modification of expressions for the waves produced by the model. From a formal point of view, we may regard the modification as an empirical introduction of a reducing factor to allow for decrease in efficiency of the element of the ship's surface as we pass from how to stern. There are now available experimental results, for wave profiles as well as for wave resistance, which made it possible to attempt such a comparison. The following work is limited to a few simple cases, and the assumptions are made in as simple a form as possible for the purpose of the calculations; these deal with the wave profile and wave resistance of a model of symmetrical form, and also with the difference between motion how first and motion stern first for a simple asymmetrical model.

Ship waves: their variation with certain systematic changes of form

1. The following paper is an examination, by analysis and by curves, of a single definite problem in wave profiles. Consider a ship model, of great draught, in which at some point in the form, at bow, stern or shoulders, for example, there is a sharp corner giving a sudden change of slope of the hori­zontal lines of the model. What is the effect on the wave profile of replacing this sudden change by a gradual change of slope of the same total amount, but distributed uniformly over any given length of the ship’s form ? Apart from direct applications, the problem is suggested by certain other considera­tions. In comparing theoretical and experimental resistance curves, I sug­gested some years ago an indirect effect of the friction belt along the sides of the ship in that it may be equivalent to smoothing out the lines of the model, especially towards the stern. From an examination of interference effects with experimental models, it has been estimated that the effective length of the model is roughly 8 per cent, greater than the actual length, and this may probably be ascribed to some such frictional effect. The present paper deals with wave profiles since measurements of surface elevation are now becoming available, though the main results so far are for a simple model with straight lines and sharp corners; such a form simplifies the calculations but no doubt introduces other complications in practice, and a small correction for the smoothing effect of a friction belt would not be likely to account for the remain­ing differences between calculation and observation. It must be noted, moreover, that there are other approximations in the theory, apart from the neglect of fluid friction, but these need not be discussed here. For these reasons no attempt has been made to apply the results of the present paper directly to experimental data, but it is hoped that the progressive series of curves will be of interest in showing the changes in profile due to successive changes of form of a definite kind.

Wave resistance : some cases of unsymmetrical forms

1. One of the chief features of interest in curves showing the variation of wave resistance with velocity is the occurrence of oscillations about a mean curve, which may be regarded as due to interference between the waves produced by the front and rear portions of the model. In various comparisons made between theoretical curves and such suitable experimental results as are available, the greatest divergence is perhaps in the magnitude of these oscillations, the theore­tical curves showing effects many times greater than similar experimental results. There are, no doubt, many approximations in the hydro-dynamical theory which preclude too close a comparison between theoretical and experimental results in any particular case, but it seems fairly certain that the divergence in question must be largely due to neglecting the effects of fluid friction. For several reasons it is useless to attempt at present a direct introduction of vis­cosity into the mathematical problem, but a consideration of its general effect suggests one or two calculations which may be of interest The direct effect of viscosity upon waves already formed may be assumed to be relatively small; the important influence is one which makes the rear portion of the model less effective in generating waves than the front portion. We may imagine this as due to the skin friction decreasing the general relative velocity of model and surrounding water as we pass from the fore end to the aft end ; or we may picture the so-called friction belt surrounding the model, and may consider the general effect as equivalent to a smoothing out of the curve of the rear portion of the model. Without pursuing these speculations further, they suggest calculations which can be made for models in frictionless liquid when the form of the model is unsymmetrical in this manner ; and the particular point to be examined is the effect of such modification upon the magnitude of the inter­ference phenomena. The first sections compare, in this respect, two bodies entirely submerged in the liquid. The form in each case is a surface of revolution ; one is symmetrical fore and aft and has sharp pointed ends, while in the other the rear portion is cut away so as to come to a fine point. By inspection of the expressions for the wave resistance it is seen that the oscillating terms are of a lower order of magnitude in the latter than in the former case.