Pulley Diameter Research Articles

Tests on V-Belt Drives and Flat-Belt Crowning

Abstract The investigations here reported were undertaken with the liberal support of the Goodyear Tire and Rubber Company, at the instigation of the company’s well-known belt engineer, the late Mr. Ray S. Carter. The immediate reason for the investigation was the desire to clear up under just what tension the front-end belt drives on certain important automotive vehicles ought to be applied to insure dependable power transmission even under sustained heavy load, and yet insure a reasonable belt life. These drives involve high speeds, small contact angles, and also small pulley diameters. Hence it was necessary to clear up the influence of contact angle on transmissive power with the small pulley diameters used. Also belt-life determinations were in order. The project then involved, in fact, all the fundamentals of power transmission with modern V-belts. While the work was in progress Mr. Paul D. Suloff, who throughout maintained current liaison between the company and the experimenters, suggested that the effectiveness of pulley crown on modern flat belts should be investigated, since with these belts customary crown practice might not be salutary for the belt. Such investigations were then added to the program. In September, 1945, the project suffered a very serious loss in the death of Mr. Carter at the height of his powers and usefulness. The work, however, continued under the detail supervision of Mr. Suloff as before, and by the spring of 1946, it was felt that the fundamentals had been determined; but for one belt size only. Experiments on other belts continued into 1947, at which time it was necessary for the author to curtail his activities. This made it impossible to give a complete experimental answer to the practical question originally posed by Mr. Carter. However, so much fundamentally important material had been accumulated that a delay in making it available to belt users would not seem justifiable. Supplementary tests (see p. 347) extend the findings to higher loads and speeds.

Effect of Operating Conditions on the Life of Rubber Belts

Abstract The variation in life of rubber belting has been a major technical problem of the rubber industry for many years. Although rubber compounds have been greatly improved, both in flexing life and aging properties, the life of belts on certain types of drives has not increased accordingly. To determine the cause of this variation, a survey was made of the performance records of belts on all types of drives. From this survey it was possible to obtain data on those drives wherein the belt life fell below the average expectancy. An analysis of this information divided these premature failures into two groups, which were designated as “external” and “internal”. The former classification includes failures due to excessive slip, high temperatures, misalignment and other detrimental operating conditions. The latter group includes those failures with no signs of external damage, and where failure involves that common condition, internal separation of the plies. A further examination of the reports on internal failures showed that practically all the drives concerned had one or more of the following characteristics: small pulley diameters, high belt tension, or high belt speed. The problem then resolved into a determination of the relative effect of these conditions on belt life.

Fifth Report of the Wire Ropes Research Committee

The present Report, like those which have preceded it, includes results which can be divided into two sections. The work of the first section follows from data recorded in earlier Reports. The Fourth Report included test results for ropes of 2 inches circumference which were tested on the larger machines, whilst the facilities for handling larger ropes allowed those consisting of more wires to be tested, since these more flexible constructions are not generally made of 1 inch circumference. Rope 20 of 2 inches circumference, 6 × 19, was included for comparison with the earlier 1-inch ropes of similar construction to indicate the importance or otherwise of the scale effect. The 2-inch rope was somewhat inferior to the poorer of two 6 × 19 1-inch ropes, Nos. 10 and 14, which differed appreciably in performance. Comparison of two 6 × 19 Trulay ropes, one about three times as large as the other, confirmed the superior life of a small compared with a large rope under corresponding conditions. Nos. 10 and 14 showed that appreciable differences may be met with in ropes supposed to be similar, so it was thought that the apparent inferiority of the larger rope was partly due to the fact that No. 20 belonged to the lower region of the range of performance which may be anticipated. Another 6 × 19 rope of 2 inches circumference, No. 26, of the same tensile strength as No. 20, was available, so it was tested to check this supposition and the probable range of behaviour. A few further tests of the 2–inch circumference ropes, arranged 6 × 19, 6 × 24, and 6 × 37, were made under more severe conditions than were covered by the data of the Fourth Report. The investigation of the effect of rope speed was carried a stage further by an attempt to discover whether slip between rope and pulley was a possible cause of a reduction of rope life at higher speeds. The lubrication of ropes has been the subject of more detailed study and an Appendix by Mr. P. G. Taigel, B.Sc. (Eng.), G.I.Mech.E., is included giving the results of many experiments and throwing further light on this important matter. The second section of the Report records the results of new work which, although it is necessarily related to, is not merely an extension of, the earlier experiments. Three flattened-strand ropes of different but typical constructions were fully tested over pulleys. A set of ropes made from the same wire but in 6 × 7, 6 × 19, 6 × 24, and 6 × 37 constructions was tested to confirm whether the pulley diameter should be related to the wire or to the rope diameter. Of another set of three ropes of similar construction and size, two were of wire having tensile strengths of 80–90 and 100–110 tons per sq. in. respectively, obtained by drawing, and the third was of wire of 80–90 tons per sq. in. tensile strength, secured by heat treatment, to confirm the effect of the tensile strength of the wire on the life of ropes and to determine whether heat-treated wire was as good as drawn wire. These ropes were made under the supervision of Mr. A. T. Adam, of Messrs. Bruntons, and were prepared for tests in connexion with his questions in the Discussion on the last Report. Experiments were carried out on a new machine designed to represent ropeway conditions. A rope under tension was traversed by a pulley taking a lateral load which caused the rope to bend through a small angle at the pulley. Comparative tests of ropes on chilled and ordinary cast iron pulleys were followed by similar tests on pulleys made of other metals or with linings at the tread. In most of the constructions dealt with, ropes were examined under an empirical static bending test and the measurements made were plotted and analysed. Little is said about the wire itself because, although more time and work have been devoted to it than to the complete ropes, many results have been negative, whilst experience has shown that hasty conclusions are likely to be wrong. It is considered that the new tests developed during this research should be given further trial before they are recommended for general use. This being the final Report of the Committee, the opportunity is taken to review the conclusions which have been drawn from time to time, and an attempt is made to stress the practical bearing of some of them.