Both the belts and pulleys are manufactured in similar materials to the standard timing belt range. In either case, it should be positioned so as to preserve the arc of contact on the powered small pulley and any adjustment to the service and arc of contact factors, occasioned by its use, made to the design calculations. By clicking Accept, you consent to the use of ALL the cookies.

Their design and performance are usually agreed between manufacturers. The letters refer to Figure 1.7 and Figure 1.12. By observation it can be seen that a 160 SPB pulley running at 1440 rev/min transmits 9.00 kW, Belt length required = 2 730 + (200 160)2 4 730 + 1.57 (200 + 160) = 2026 mm (SPB 2020 will suffice), From BS 3790, belt length factor for SPB 2020 = 0.93, N=221.39.000.990.93=3.45(say,4belts). Pulleys employing split-taper bushings are most convenient for installation and removal in that they avoid the need for interference fits, keys, etc. 1.5(b). BS 3790: 1981 specifies six sizes of classical belt, designated Y, Z, A, B, C and D, and four sizes of wedge belt, SPZ, SPA, SPB and SPC. The V-Belt, in its different forms, became the generally accepted method of efficiently transmitting power. The Flexible section: withstands bending stress without fatigue. The wedge belt differs from the classical belt, from which it was developed, in having a greater height-to-top width ratio.

The driven pulley can be set at any angle in relation to the driving pulley provided it is turned about point A, as indicated by the dotted lines. Belts should initially be tightened to the higher values. The cross-sectional dimensions of the sections are shown in Table 10.1 It should be noted that while the overall dimensions are given for recognition purposes, the pitch dimensions are used for the calculation of power, centre distance, etc. See Figure 18.3. Figures 10.56 and 10.57 show the tooth profile and dimensions for L and H pitch. Improvements in materials with the introduction of rubber and rubber/cotton composite belts followed by plastics belts ameliorates some of these disadvantages. Nevertheless, there are still some applications for flat belt drives and the following information will help the engineer to arrive at a belt size for specific applications. This conformity with ISO permits a high level of international interchangeability. The chart gives the groove gauge diameter in terms of the nominal wire rope diameter plus a percentage thereof. 170 pitches, C=1424mm. Any sheave with a groove smaller than this must be re-grooved or, in all likelihood, the existing rope will be damaged. The drives are quiet in operation and the use of multiple belts removes the likelihood of a sudden breakdown. Tooth form and size are covered by BS 4548. Progress in power belts has been considerable within the last decade and much of this effort has been concerned with finding improved materials more suited to specific types of transmissions. Neeraj Niijjaawan, Rasshmi Niijjaawan, in Modern Approach to Maintenance in Spinning, 2010. Figure 58.4. Multigroove pulley cross section. These are made from thin metal strips ranging from carbon steel through beryllium copper to stainless steel, titanium and, in the case of high temperatures, Inconel. If the measured force falls within the values given in Table 11.5 the drive tension should be satisfactory. The drive should be re-tensioned at regular maintenance intervals.

Laundry machinery. Therefore, the code symbol 24H200 represents a timing pulley with 24 grooves, 1/2-inch pitch and accepts a 2-inch wide belt. The power rating given in the table for the particular pulley diameter and shaft speed is multiplied by the correction factors for belt length, arc of contact, etc., and then divided into the design power (actual power service factor) of the drive. Power ratingsTable 10.4 shows typical power ratings for each of the belt sections. The load must not in any case be applied beyond the end of the fan or motor shaft extension. There was still the need for drives, but these were considerably shorter while the power requirements were still rising. The HTD belt was developed to handle the higher torque capabilities normally associated with chain. This latter gauge is intended to act as a sort of no-go gauge.

Reduce the centre distance until belts can be placed in the pulley grooves without forcing. Both belt and chain CVT systems fall into the category of friction-limited drives as their dynamic performance and torque capacity rely significantly on the friction characteristic of the contact patch between the belt/chain and the pulley. For light loads, and where small-diameter pulleys are in use, a flat belt made from woven fibres provides a highly flexible drive. Pulleys must be balanced either statically or dynamically, depending on the rim speed and ratio of face width to diameter. Normally, pulleys should be chosen which will give a belt speed in the 1520 m/s speed range and are of adequate diameter in relation to the motor bearings (see Table 10.4). Similar details are usually given in the catalogues of manufacturers, some of whom operate a technical advisory service. It is recommended that only direct coupled drives be used for motors in sizes D160M and above at 2-pole speeds. Before installing onto a pulley, it is always a good idea to place each belt into its pulley groove. Experience has clearly demonstrated that the service life of the wire rope will be materially increased by strict adherence to these standards. A Fenner TaperLock bushing for securing a large pulley to a shaft. Papermill beaters. Power rating of curvilinear tooth belts, Figure 1.9. Power rating of Vee-ribbed belts, Figure 1.7. Z-SPZ) dimension h can be reduced by 20% if it is intended to use only classical belts. Nilabh Srivastava, Imtiaz Haque, in Mechanism and Machine Theory, 2009. Automotive belt drives are selected and operated under quite different conditions to industrial belts and are the subject of BS AU150: 1984.

Nicks, scratches, or gouge marks on a pulley can cut into a belt. Mechanical Design Engineering Handbook (Second Edition), Modern Approach to Maintenance in Spinning, The cover is made of fabric molded with rubber in order to provide strong abrasion resistance on the, Before installing onto a pulley, it is always a good idea to place each belt into its, Mechanics and Calculations of Textile Machinery, matrix which is encased in a wear-resistant cover. Power rating of trapezoidal tooth belts, H. Zhu, W. Fan, in Journal of Sound and Vibration, 2021. Figure 10.60 shows the basic dimensional details. The very first item to be checked when examining sheaves and drums is the condition of the grooves (Figs. Raw-edge V-BeltsRecent years have seen the development of the raw-edge V-Belt. When starting up, a new drive should be tensioned to the higher value to allow for stretch during the running in period. By continuing you agree to the use of cookies. ScienceDirect is a registered trademark of Elsevier B.V. ScienceDirect is a registered trademark of Elsevier B.V.

In many industries such as food handling, strict process restrictions do not permit the use of lubricants in close proximity to the products being processed. Light-duty conveyors. Depending on the application, timing belts have considerable advantages over chains, gears, V-Belts and flat belts due to one or more of the following features: Owing to the use of a fibre-glass cord the timing belt has no stretch whatsoever in service, and this in itself eliminates the necessity of expense on automatic take-up devices and/or periodic maintenance. With cotton ropes, the pulley grooves should be highly polished to minimize the wear of the cotton. The accepted method of belt tensioning is by the application of a force normal to the belt spans, at the span centre, to achieve a stated deflection. This website uses cookies to improve your experience while you navigate through the website. Table 11.5.

Special drives for shafts at right angles and V-flat drives, where the driven pulley is flat and can be part of the machine (such as a tanning drum), can be designed, although particular criteria must be observed.

The idea of cogged, rubber driving belt for synchronous power transmission originated with the Singer Sewing Machine Company in America. Narrow V-Belts (better known as wedge belts) have a narrower profile than classical V-Belts, with a relative height of approximately 0.9. The pulley surfaces and especially the groove sidewalls should be machined such that the surface finish is a maximum of 3-2 m when determined by the method described in BS 1134. When the belt teeth in mesh are 5 or less the shear strength of the tooth becomes the critical factor in design, and this invariably results in an increase in belt width. However, the 3D FE models or multibody dynamic models can be used to accurately describe the contact mechanics between a V-ribbed belt and pulley if the deformations of the belt ribs are ignorable. 1, 2 and 3). 6, 6, 1.0, 1, 3kW, 9.525mm pitch simple or 8mm duplex, 136.7 pitches, 138 pitches, 306.7mm. Printing machinery. For belt speeds above 40 m/s special pulleys may be necessary. Positive-displacement blowers. Pump pulley: 80 groove pulley with a 55-mm belt width. As shown in Figure 1, the gauge should contact the groove for about 150 of arc. The number of belts required for a particular drive can be obtained using the power table for the selected type and size of belt. Frequent installation faults for vee rope drives. Illustrating the various dimensions of a sheave and the use of a sheave gauge. These drives were very tolerant of misalignments and were also highly flexible since they could be crossed to give opposite direction of rotation and could be used to drive shafts which were not necessarily in the same plane (see Figure 10.50). We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Hence, the creep theory and the shear theory only suitable for one dimensional or planar numerical models of V-ribbed belt drives without considering the specifications of the contact deformations between the belt ribs and the pulley grooves. These profiles, which are defined in BS 3790, also conform to ISO 4183. The V-belts are available in A, B, C, D, E sections. If the belt top is deeper in the groove, the groove or belt is worn, which can shorten the remaining belt life by as much as 50 per cent. Figure 58.5 shows a belt gage, an alternate means of determining belt wear, which measures belt total width (TW).

Belt deflection measurement. As in gears, the ratio of speed of driven to drive shaft is a matter of pulley diameter and is derived from the following formulae (see also Figure 10.52): The length of a belt is derived from the formula: Allowable power that can be transmitted by a particular belt is best derived in conjunction with manufacturers' literature, as it will be dependent on the choice of belt material. The timing belt drive requires no lubrication and this allows for very substantial economies in initial drive design since oiltight housing and gear cases, seals, lubrication lines and accessories are all completely eliminated, while, at the same time, maintenance costs are also drastically reduced. Hammer mills. The original form of round belting for power transmission was the rope drive using cotton ropes and, while this form of drive is still used, the modern round belt is usually elastomeric or woven from synthetic fibres. The rope or V-belt does not rest on the bottom of the groove but wedges itself into the groove. All timing pulleys up to and including 48 grooves in L and H pitch are supplied with flanges.

Stock lengths, varies with manufacturer, other lengths to special order. A general rule for aligning belt pulleys connecting non-parallel shafts. Light alloys are not usually employed for continuous industrial duty because groove wear would cause damage to the belts. number of belts per pulley width of one. Correct vee belt tensions: required force N at centre of span for belt speed (To obtain kgf divide N by 10 to give approximate value). d= pitch diameter of smaller pulley (mm), R= prime mover speed driven machine speed. Even on perfectly aligned pulleys, a standard construction timing belt will track, and it is for this reason that one pulley (generally, the smaller of the two) is flanged to prevent the timing belt 'walking off the drive. 19.05mm pitch simple BS chain drive. For better comprehensibility, the literature reviewed has been categorized into different sections. The drive should be re-tensioned at regular maintenance intervals. From: Mechanical Design Engineering Handbook (Second Edition), 2019, WTW (Bill) Cory, in Fans and Ventilation, 2005. Similarly, the size of the no-go gauge is given, against which worn grooves are judged. The simplest form of power transmission is probably the belt drive. Hence, excitation mechanisms exist, which are strongly connected to the polygonal action of chain links. Punches, presses and shears. Childs, in Mechanical Design (Third Edition), 2021. When replacing belts always order a matched set and do not mix old and new belts. The endless V-Belt drive, used either singly or in multiples, has a very wide range of uses and has applications in almost all types of machinery. Make adequate provision for tensioning the belts during their life. These sheave groove cross-sections represent three wire rope seating conditions: A is a new rope in a new groove, B is a new rope in a worn groove and C is a worn rope in a worn groove. Dough mixers. Such inspections usually include the drum, sheaves, and any other parts that may come into contact with the wire rope and subject it to wear. Light duty Agitators for liquids, blowers and exhausters. In general, for all pulleys operating below 10 m/s rim speed, and for pulleys with face widths half or less of the diameter operating below 20 m/s rim speed, static balancing is adequate. *** Minimum pulley diameters vary with belt thickness, H. H can take a wide range of values for any k1%, as the ratio of friction material to tension member thickness varies with application. 200 pitches, C=1360mm. Pitch dimensions must be regarded as absolute and used for the derivation of other dimensions, which can be nominal or toleranced. Make adequate provision for tensioning the belts during their life. It is the most widely used type of belt, particularly in automotive and industrial machines. Unlike a belt CVT, the contact forces between the chain and the pulleys are discretely distributed in a chain CVT drive. The four separate groups of driving machines are defined as follows: Table 10.3. D1=212mm, D2=100mm, speed ratio=4.72, C=1805mm (SPB5600), 1 belt. Figure 1.8. Raw-edge V-Belts are normally manufactured in the wedge belt sections but they are also available from some manufacturers in the classical sections. There is a more even distribution of the tension forces between the reinforcing cords and thereby a higher power rating compared to classical V-Belts of the same top width. This causes vibrations in the entire chain CVT system, which further affects its dynamic performance. The wedging action of a V-belt in a, Mechanical Engineer's Reference Book (Twelfth Edition). Note:Although contemporary practice uses pitch dimensions for all calculations, in the past it was common to define classical belts by inside length. Reduce the centre distance until the belts can be placed in the pulley grooves without forcing. In this connection, a general rule for aligning belt pulleys connecting shafts which are not parallel is for the centre of the face of the driven pulley to be aligned with the centre of that face of the driving pulley from which the belt leaves, as at A in Figure 10.51 The manner in which the belt passes over the pulleys is indicated by the arrows showing the direction of rotation. The belt profile also allows for very high belt speeds of up to 60 m/s, although drives of above 30 m/s must be carefully considered because of pulley material. Centrifugal pumps and compressors. Conveyors (drag-panscrew). As with chain, the tooth pitching became standardized and the early types were based on the inch system of units. When the sheave is re-grooved, it should be machined to the dimensions for recommended minimum new groove given. Sawmill and wood-working machinery.

These cookies do not store any personal information. For new or re-machined grooves, the groove gauge is nominal plus the full oversize percentage. Any cookies that may not be particularly necessary for the website to function and is used specifically to collect user personal data via analytics, ads, other embedded contents are termed as non-necessary cookies. (See also Figure 10.54). V-belts comprise cord tensile members located at the pitch line, embedded in a relatively soft matrix which is encased in a wear-resistant cover. While most of these belts are made from various polymers in combination with fibre reinforcements, there are also all-metal belts. Figure 10.50. To obtain kgf divide N by 10 to give the approximate value.

In the cushion section, adhesive rubber binds cord firmly and acts as a binding force between topping and base section. Different belt constructions are available which provide anti-static capacity, oil tolerance and flame-resistance properties. Textile machinery. R Keith Mobley, in Plant Engineer's Handbook, 2001. However, when cogged belts are used in larger pulleys the contact area and therefore the power-transmission capability are somewhat reduced. These cookies will be stored in your browser only with your consent. These belts are not in common use but offer potential in new projects. When flexing round a pulley, V-link belting does not suffer distortion as does the solid V-Belt; adjacent links slide over one another and there is little or no internal stress generated and in consequence, lower heat. Pulleys must be produced from materials with adequate strength for the power and speed requirements of the drives. Arc of contact correction factorThe arc of contact x on the small pulley can be calculated from the following formula (see Table 10.6): Note: Arcs of contact below 120 should not be used without confirmation of the drive details by the belt manufacturers. Table 10.3 gives the factors for periods of up to 10 hours, 10 to 16 hours and over 16 operational hours per day. Figure 10.53. Necessary cookies are absolutely essential for the website to function properly. N. Gokarneshan, C.B. Both flat belts and V-Belts lose a very small amount of speed (less than 1%) due to belt creep (a condition not to be confused with slip) which is due to the change in belt section and tension as it moves around the pulley. Today glass-fibre reinforcement is common and aramid is used if maximum capacity is required. Check that the vee belts are correctly tensioned: Apply a force at right angles to the belt at the centre of the span. Unlike any other type of drive, the pitch diameter of the timing pulleys is so arranged that it is actually in the centre of the flexing part of the timing belt where the load-carrying cords are situated. To avoid the danger of imposing excessive stresses, it is advisable to consult the fan and motor manufacturers for all drives on shafts above 48mm diameter.

Correct vee belt tensions: required force N at centre of span for belt speed, Figure 11.13. (2) If idler pulleys are used, add the following to the service factors: (a) idler pulley on slack side, internal, 0; (b) idler pulley on slack side, external, 0.1. 25.4mm pitch simple BS chain drive. The teeth have an involute shape the same as gears to ensure smooth, rolling contact as the belt enters and leaves the pulley. Generators. Dirt abrades the belting material and wear grooves cause a belt to bottom-out in the groove, resulting in slippage and ultimate damage to the belt. Mazzella Learning Center Inspection of Wire Rope Sheaves and Drums. (a) Standard involute belt tooth profile showing loading concentrated at the point of contact; (b) HTD curvilinear design showing improved contact and substantial root stress distribution. The d values in the Figures 1.8 and 1.9 are nominal. XL is generally restricted to small business machines such as electric typewriters and photocopiers and XXH tends to be uneconomical for the power capacity, leaving L, H and XH in general industrial use. A force below the lower value indicates under-tensioning. To check the size, contour and amount of wear, a groove gauge is used. Pulleys should always be fitted so that the effective centre of the belt or rope is as near as possible to the motor or fan bearing. However, it will be time-consuming for these models to calculate transient responses of V-ribbed belt drive systems. V-Belt pulleys:Figure 10.52 and Table 10.2 show the standard profiles, which in four cases are equally suitable for either classical or wedge belts. Figure 10.54. Belts can be round, flat, V-form or toothed and some designs incorporate features of more than one type. Exciters. Because stable length is essential for synchronous belts they were originally reinforced with steel. Tension relationship between the slack side of the belt (which should be above the pulleys) is given by: Pulleys should slightly exceed the belt width and should be slightly crowned. The theoretical pitch line of a HTD belt lies within the tensile member (see Figure 10.63). There are five pitches generally available: XL, L, H, XH and XXH. Faced with this dilemma, establishing a model with both high accuracy and efficiency is the endeavor direction for researchers. Electric motors became smaller and more efficient and their price was low enough for them to be economically used on the basis of one motor to each machine, or indeed several motors to provide the power for different tasks in a single machine. The width, thickness, minimum sheave diameter increase from section A to E, in other words, belts become heavier from section A to E. James Carvill, (Section 10.2), in Mechanical Engineer's Reference Book (Twelfth Edition), 1994. Under normal conditions, machines receive periodic inspections and their overall condition is recorded. The ratings are based on the range of motor pulley diameters normally associated with each section and the speeds are for the faster shaft. 1.13. Second, since belt length can be adjusted by increasing or decreasing the number of links, fixed pulley centres can be used. 94 pitches, C=603.1mm. Locate the smaller pulley groove number speed combination and note the power rating. If absolute synchronization is required then some type of geared drive is called for. Ideal belt speed is around 18 m/s. 19.05mm pitch simple BS chain drive. The core supplies the tensile strength and the casing forms the friction surface in contact with the pulleys. Pulleys are also recognizable by type, which refers to the particular design of pulley. Fans up to 7.5 kW. The wedging action of a V-belt in a pulley groove results in a drive which is more compact than a flat belt drive, but short centre V-belt drives are not conducive to shock absorption. For wedge belts only the latter should be used. Senthil Kumar, in Mechanics and Calculations of Textile Machinery, 2013. A V-belt or rope meshing in a V-shaped groove of the pulley increases greatly the frictional resistance to slipping, for a given maximum belt tension, as compared to flat belt. If the measured force falls within the values given in Table 18.5 the drive tension should be satisfactory.

You also have the option to opt-out of these cookies. Figure 58.4 is an illustration of how a V-belt should sit in the pulley groove. The values are only a guide and can vary considerably and it is prudent to consult the Standards or manufacturers' catalogues for a precise selection. Pulverizers. A further advantage is that they can be fitted to pulleys without the need to first reduce the centre distance. performance, slip behavior, efficiency, configuration design, loss mechanisms, vibrations, operating regime, etc. To this are moulded the uniformly spaced and pitched neoprene teeth.

It also permits installation in otherwise inaccessible locations. On the other hand, in a chain CVT system, the plates and rocker pins, as depicted in Fig. The V-Belt is manufactured with a core of high-tensile cord embedded in rubber or synthetic rubber and encased in a fabric and rubber reinforcement. Figure 1.5. Note: These figures are reasonable for most applications but should be checked with the manufacturer for specific installations. Applicationally, V-Belt drives provide a high degree of flexibility, with a wide choice of speed ratios and shaft centre distances. 1 and 3). These newer synchronous belts with rounded curvilinear tooth design are known as HTD, which stands for High Torque Drive. The high performance of modern belts, especially wedge, can only be realized by proper tensioning and this is particularly important in the early life of the drive when bedding-in and initial stretch are taking place; nothing damages belts more rapidly than the heat generated by slip. Figure 10.59 shows a typical flanged pulley.

Selection of belt drives BS 3790: 1981 contains all the information necessary to design a drive; power ratings, standard pulley diameters, service factors, correction factors for belt length, arc of contact and speed ratio. In general, V-link belts are more expensive than the endless belt but some economic advantages may be gained by holding a stock of links rather than a variety of endless belts. This concept was developed and applied to other machinery and became more generally accepted during the 1950s. (see Figure 11.12), Figure 11.12. Belt: 14MXP-2310-55 torque drive plus three belts, 2310mm long 55mm wide belt. Bucket elevators. When multi-belt drives are installed, matched sets of belts, coded for length, must be used to ensure correct load sharing.