Belts

How to choose a Belt Drive

Contents:1. Read the introduction to the guide 2. Specify the environment and operating conditions 3. Specify the performance of the belt drive 4. Select the belt drive required 5. Install the belt drive

Useful information

British Standards Belt drive types currently available Power ranges Belt drive manufacturers Further reading

1. Introduction

Use this Guide to determine the attributes required of a belt drive to meet a specific power transmission need and then to Select a drive from those offered by manufacturers.

The successful Selection of a suitable belt drive is the result of matching the requirements of the power transmission system with one of the range of belt systems offered by the manufacturers. Thus, information about both the system and the hardware available is necessary, and the Selection process entails six consecutive stages:

1. Gathering information about the system 2. Deciding on influential factors 3. Establishing limits of acceptability for factors 4. Collating information from manufacturers 5. Selecting a suitable element 6. Seeking follow-up advice

Reference should be made at every stage to the Product Design Specification (PDS) for the system (all the relevant factors should be described in a well written PDS).

Note that, before embarking on the Selection process, you should ensure that the need for a belt drive, as distinct from other forms of drive, has been carefully considered. The Guides at higher levels in the Mechanical Power Transmission Series provide assistance in this process.

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1.1 Gathering information about the system

The most important information about a system is usually related to its purpose and to the constituent elements, life, performance, environment, and economic situation for which it is required.

This information is needed in order to understand the total system so that the belt drive Selected is consistent with the rest of that system. The temptation for the engineer to consider only purpose, performance and perhaps environment should be strongly resisted.

Although this stage is sometimes difficult and time consuming, it must be completed thoroughly if an appropriate unit is to be identified.

1.2 Deciding on influential factors

Factors which influence the choice of belt drive must now be identified. A listing of most of the important and common factors is given in Section 2. Not all the factors described are important on every occasion, so careful study of the system is required to ensure that those considered are actually relevant. Reference must be made to the Product Design Specification for the system.

1.3 Establishing limits of acceptability for factors

Each factor should be defined in terms which are as objective as possible. Thus, where appropriate, numerical information should be given, terms must be explained, and vagueness avoided. Then the boundaries of satisfaction must be defined for each of the chosen factors. This helps the designer to decide which belt drives meet the requirements in each respect.

The boundaries must be numerical whenever possible. When subjective judgements are necessary, a means of comparison must be established.

1.4 Collating information from manufacturers

Manufacturers' data should now be collected and arranged into a suitable format. There is a finite number of belt drive arrangements available from manufacturers, and the Selection process is heavily constrained by the form and content of the information presented by them and by the range of catalogues available to the designer at the time.

There is a good case for maintaining a 'rolling' catalogue library, or data on microfilm/computer, since this stage can be very time-consuming if a unique set of data is collected separately on each occasion. Data on, for example, size, performance, and cost can be noted in numerical form, giving a range where appropriate. In the case of less objective data, a rating may be shown based on advice or opinion gathered.

1.5 Selecting a suitable element, based on best match

Optimising the choice of a suitable element is now a process of finding the best compromise (in the opinion of the designer) between the priorities of the system and the availability of the hardware. As far as the factors involving numerical data are concerned, some yield a 'go/no-go' situation which will eliminate those which are too costly, too heavy, too big etc.

Other requirements involving more subjective data should be compared on the basis of their ability to meet the criteria as laid down in the Product Design Specification. This may be an iterative process which converges on the best compromise.

The evaluation technique used here will be similar to that used elsewhere in the design activity. References for further reading given at the end of this Guide will elaborate on the details of variety of techniques.

1.6 Seeking follow-up advice

Further advice on the details of installation or specifying and ordering will be required from the manufacturer's information. This would normally be available from the catalogue, but sometimes it is necessary to communicate directly with a representative of the company.

2. Specify the operating conditions for the belt drive

Although this stage is sometimes difficult and time consuming it must be completed thoroughly if an appropriate unit is to be identified. You must understand the system in which the belt drive will operate so that the drive you Select is consistent with the rest of the system.

The prime function of a belt drive system is to transmit torque between two shafts, often with a change of angular velocity in the process.

The performance of the belt drive is thus concerned with the power it can transmit.

This is often expressed in terms of the torque and speed related to the two shafts. The speed ratio between them is also important, and there are limits to the ratio obtainable for one stage with a given belt type.

Ensure that the units used are appropriate for the parameters quoted.

Ensure that the units used are appropriate for the parameters quoted.

Other factors affecting belt system Selection are:

1. The environment in which the belt drive must operate 2. The consequences of failure 3. Commercial factors 4. Operation and maintenance

2.1 Specify the environment

Since most belts are manufactured from rubber, or polymer-based materials, they tend to be particularly susceptible to environmental conditions.

The temperature, humidity and pollution by oils and greases should be noted and suitable materials Selected.

Vibration and shock loads can also cause belt failure prematurely.

Although the elasticity of the belt may help to reduce the dynamic loads on the system the belt itself will suffer.

Under such conditions the belt should be inspected and maintained regularly.

2.2 Specify the consequences of failure

These must be estimated so that an adequate allowance for a safety margin can be made.

Two aspects of failure should be considered: its likelihood, and its consequences. The reliability of the belt drive, its duty and required service life will help to determine the former. The manner of failure and the belt type will be concerned with the latter.

Belts may fail catastrophically by fracture (especially if initial tension is too high or they are overloaded) or gradually (if tension is too low and the belt slips on the pulley).

In the latter case there may be a danger of fire since great heat can be generated.

All belt drives should be guarded so that access is prevented and the consequences of failure are contained.

2.3 Specify the commercial considerations

Commercial factors include:

The price of the belt system, with its associated pulleys and shaft fittings Its availability, both initially and for replacement parts The need to standardise on belt type, section and length, either on a single product or

within a range of products.

2.4 Specify the operating factors

Factors relating to operation include the ease which which belt drives can be fitted and dismantled. These procedures are crucial to a belt drive's economic operation. Most standard belt sections are supplied in ‘endless ‘ form and require to be fitted to the pulleys 'in situ'.

Access to allow this and regular inspection and maintenance must be allowed.

Dismantling for replacement implies the same requirement.

It should be noted that different belt section types are not generally interchangeable and pulleys of a matching section must be used.

Geometrical factors also have a crucial effect on belt drive performance. For 4example, the space available may help to determine the preferred belt configuration. The axial width available, the shaft centre distance and the pulley diameters required will affect the final choice.

Additionally, it is most important to provide the means for the belt tension to be adjusted both initially and during service. This may be done either by adjusting shaft centres or by providing a spring-loaded ‘jockey’ pulley.

Misalignment between pulleys is a major cause of premature belt failure, and provision for ensuring correct alignment should be made.

3. Specify the performance required

Each factor defining the required performance should be specified in terms that are as objective as possible. Thus, where appropriate, numerical information should be given, terms must be explained and vagueness avoided.

Factors to be considered are:

Duty/Service factor Nominal power Nominal speed Nominal speed ratio Belt length Power factors Number of belts Other

Note that estimates of speed and speed ratio should be used at at early stage to Select a suitable belt type . This initial Selection procedure should be implemented before a detailed investigation of requirements is undertaken, since it directs the designer's efforts in an appropriate direction.

Selection procedure 3.0 Belt type: initial Selection

Estimates of belt speed and speed ratio can be used as shown below to make an initial Selection of the type of belt required.

If a constant speed ratio is important, use a Toothed belt

if belt speed < 30 m/s, use a Vee belt

if belt speed < 40 m/s and,- speed ratio < 7:1, use a Vee belt- speed ratio < 8:1, use a Wedge belt

otherwise,if speed ratio > 8:1 or belt speed > 40 m/s, use a Flat belt

3.1 Duty/Service factor

Types of duty are categorised as follows:

Light duty Medium duty Heavy duty Extra heavy duty

The type of duty determines the service factor involved (S). Service factors for typical driving and driven machines and for a variety of duties are shown in the table below.

Further allowacne may be required if the consequences of failure are particularly serious. Some manufacturers' catalogues may give further advice on suitable values.

3.2 Nominal power

The nominal power to be transmitted (kW) is the demand from the driven machine. Calculation of the nominal power (P) allows the determination of design power (P').

Design power is the product of the nominal power and the service factor (S) .

The rotational speed of the two shafts (rev/min) or of one of them with the speed ratio must also be known.

3.3 Nominal speed

In order to make a preliminary choice of belt section dimensions, the nominal speed (N) of the driving device must first be determined.

The preliminary dimensions can then be chosen by considering the belt type and the nominal speed (N) in conjunction with the power rating ranges for belt types.

3.4 Nominal speed ratio

The speed ratio is a function of the pulley sizes. The minimum recommended pulley size for a given section depends on the flexibility of the belt and the mass/unit length.

Pulleys are normally manufactured in standard sizes so the choice of the driving pulley should be the smallest standard size which is recommended for the chosen belt section such that the ratio obtained is near to the required value when matched with a larger standard size pulley.

Pulley sizes are normally based on a pitch diameter, which may be less than the outside diameter.

Minimum pulley diameters recommended for a range of belt types are as follows:

Vee 67 mm Wedge 60 Flat 40 Polyvee 18 Timing 16

3.5 Belt length

Belt Length (L) is a function of shaft center distance and pulley diameters.

Most belts are made in standard lengths which are cheaper and easier to obtain than non-standard ones. Some (particularly plain flat belting) can be supplied in straight lengths which can be joined round the pulleys.

However, these are recommended only if the assembly of a continuous belt is difficult.

The nominal length calculated above should be modified to the nearest standard length, and the shaft centre distance amended to suit.

Manufacturers’ catalogues should be consulted to determine the standard lengths available for specific belt types.

3.6 Power factors Allowable Power per Belt (Pb) is a function of the dimensions of the belt section and is obtainable from the manufacturer's catalogue. Plain flat belting is often rated as power per width dimension (kW/mm).

Power Correction Factors may be required to compensate for:

Speed ratio length of belt/pulley contact Total length of belt

Appropriate manufacturers' catalogues will provide values and method of application.

3.7 Number of belts

Number of Belts (X) refers to the total number of separate belts or the total width of (flat) belt required. This is given by:

X = P'/Pb

In the case of Vee type belts the value of X should be rounded up to the nearest whole number. For flat belt types the value of X should be rounded up to the nearest standard belt width available from the manufacturer.

3.8 Other factors

Further refinement of the belt choice will result from consideration of commercial and reliability factors such as cost, availability etc, and belt life, pulley wear etc.

4. Select the type of belt required

Select a suitable belt type, using 'best match" criteria. see (1.5).

The table below indicates the maximum performance to be expected from different belt types.

Typical belt performance

5. Installation

During the design of the installation for a belt drive, particular attention should be paid to the following:

Maintenance of initial tension (where required) Adjustability of tension Pulley alignment Ease of removing and fitting belt Protection from pollutants (lubricants, acids, grits etc) Guarding from interference with operators' clothing, person etc

7. British Standards

A Selection of relevant British Standards is given below.

BS No 351:1976 (1985) Specification for rubber, balata or plastics flat transmission belting or textil construction for general use (technicall equivalent to ISO22)

BS No 1440:1971 Endless V-belt drive sections (withdrawn replaced by 3790)

BS No 3790:1981 Specification for endless wedge belt drive sections and endless V-belt drives (techcnically equivalent to ISO 155, 254, 1813, 4183, 4184, 5292)

BS No 4548:1970 Specification for synchronous belt drives

8. Belt types and features

Five main types of belt are currently available. Details of their construction and performance are shown in the table below. An initial Selection of belt type should be made at an early stage of the design, based on estimates of speed and speed ratio.

Belt types and features

9. Power rating ranges for belt types

The power rating charts for the following belt types are supplied with this guide (courtesy of J.H. Fenner Ltd):

Vee

Wedge

Timing

For each belt type, the range of powers covered by a given belt section is denoted by a thick line and designated by a code. The elements of the code for Vee and Wedge belts are as follows: a number (eg: 200)

shows the pulley pitch diameter limit a number (eg: 2)

shows the number of belts a letter (eg: C)

shows the belt section size For Timing belts, the code simply denotes the section size.

Other manufacturers may show similar information in a slightly different format.

The rating chart for Timing belts shows similar information from the same manufacturer. This time, the chart is confined to a particular width of belt (25mm) and wider belts should be uprated pro-rata.

A rating chart for Flat belts is also supplied, courtesy of Stephens Miraclo Belting Co. Belt

codes here denote section size, and power ratings are given per unit belt width.

10. Manufacturers

The following table is a guide to manufacturers of drive belts and associated equipment. It is not intended to be exhuastive. Further details can be obtained from an engineering Buyers' Guide or from Technical Indexes.

Timing Belts

Important Note:..The notes below are intended to be concise informative guidance notes.  Manufacturers literature and the relevant standards provide the necessary detailed information required for detail design.  I have included links to sites providing good quality information on this topic.

IntroductionSynchronous / Timing belts are basically endless flat belts which pass over pulleys- the belts having grooves which mate with teeth on the pulleys.  These belt drives, unlike flat and vee belt drives are positive.   Any slip of the belt relative to the pulleys is minor in degree and is due to belt stretch, or erosion of the grooves.  These belts are used for power transfer and for synchronised drives to ensure that the driven pulley is always rotating at a fixed speed ratio to the driving pulley.

The first synchronous belts had a trapezoidal tooth profile, and is identified as timing belts.   The belt tooth profile is a trapezoidal shape with sides being straight lines    The profile of the pulley teeth which mates with the belt is involute.  These belts are based on imperial (inch) pitch sizes and can provide power transmission up to 150 kW.

The development of the classical timing belt with has a rounded tooth (curvilinear tooth profile) and is identified as as the high torque drive, or HTD.  Advantages of this belt design include..

Proportionally deeper tooth; hence tooth jumping or loss of relative position is less likely Lighter construction, with consequent reduced centrifugal loss. Smaller unit pressure on the tooth since area of contact is larger. Greater shear strength due to larger tooth cross section. Lower cost as a narrower belts will handle larger load. Installation tension is reduced resulting in lower bearing loads.

HTD sprockets have metric pitches (3 5 8 14 & 20) and can transmit up to 1000 kW.

The most advanced synchronous belts, has a modified rounded tooth profile with a higher tooth angle and shallower tooth.   These belts e.g Gates Powergrip GT have available pitch sizes of 2mm, 3mm & 5mm and can powers up to transmit up to 600 kW .   The belts have the advantages that they provide a smoother drive at higher accuracy,

A correctly designed and installed synchronous belt drive should operate successfully for between 8000 and 12000 hrs and have an operating efficiency of about 98%.

Synchronous belts have a number of advantages such that they are often used for applications not requiring shaft synchronization.   Their section and flexibility enable timing belts to operate very well on miniature drives and in applications involving high speeds or small pulleys.   They are extremely efficient when correctly installed.   They can also be specified to continuous high loads.    For these reasons, synchronous belts have proved to be cost effective in non-synchronous applications as drives for power saws, motorcycles, and domestic appliances.

The disadvantages of synchronous belt drives are that they are generally more costly compared to other belt drive options and the require accurate alignment of the pulleys for efficient reliable operation

ConstructionBeltsSynchronous belts are made with elastomer e.g natural rubber,neoprene, polyurethane, polychioroprene, core with reinforcement to provide increased tensile strength.  These belts were originally reinforced with steel to provide the necessary strength.   In modern drives the most common reinforcement is glass fiber, but aramid is used if maximum capacity is required. Synchronous belts are often provided with nylon facings to provide the necessary wear resistance and can include conductive coatings.

PulleysSynchronous drive pulleys are often made of ductile or cast iron.   Aluminum is a often selected for drives that require low weight.   These applications can include high speed drives with low inertia.   Steel(and Stainless Steel )is preferred to iron when the drive will exceed the safe operating limits for cast iron (2000 mpm) or ductile iron (2500 to 3,000 mpm).Plastic pulleys e.g. nylon are low-cost options when power requirements are low as in office machines or home appliances such as vacuum cleaners.   Plastic gears may also be acceptable when it is acceptable that the belt service life is short, as in some power tools, or lawn and garden equipment.

Pulleys are mounted to shafts using pins, keyways or by using proprietory shaft locking bushes such taperlock bushes. Pulleys can have one or two flanges to ensure the belts are retained in place.   For drives with horizontal pulley axes it is normal to have two flanges to retain the belt (two flanges on one pulley or one flange on each pulley on opposite sides).    On pulleys with vertical shaft axes the lower face of each pulley should include a flange and one pulley should include two flanges.

Relevant StandardsThe British Standard for timing belt drives wasBS 4548:1987 :Specification for synchronous belt drives for industrial applications . This standard is still in use but is declared as obsolescent the current standard in europe for timing belt drives isISO 5294:1989: Synchronous belt drives -- PulleysISO 5296-1:1989:1989: Synchronous belt drives -- Belts -- Part 1: Pitch codes MXL, XL, L, H, XH and XXH -- Metric and inch dimensionsThis is not equivalent and belts and pulleys to the British Standard are not interchangeable with the ISO standard.

Basic Timing Belt ParametersClassical Timing belts

BeltSection Meaning Pitch

mmWidths Available

mm

MXL Extra  Light 2,032 3,05   4,826   6,35

XL Extra  Light 5,08 6,35   9,652

L Light 9,525 12,7  19,05  25,4

H Heavy 12,7 19,05  25,4  38,1  50.8  76,2

XH Extra heavy 22.225 50.8  76,2 50.8 76,2 101,6

127101,6

XXH Double extra heavy 31,75 50.8  76,2  101,6  127

HTD- Curvilinear

BeltSection Designation Pitch

mmWidths Available

mm

3M 3mm High Torque Drive 3 6 9 15

5M 5mm High Torque Drive 5 9 15 25

8M 8mm High Torque Drive 8 20 30 50 85

14M14mm High Torque Drive

14 40 55 85 115 170

20M20mm High Torque Drive

20 115 170 230 290 340

GT - Curvilinear

BeltSection Name Pitch

mmWidths Available

mm

2MR (Gates) 2mm High Torque Belt 2 3 6 9

3MR (Gates) 3mm High Torque Belt 3 6 9 15

5MM (Gates) 5mm High Torque Belt 5 9 15 25

Note : The various notes below relate to the classical timing belt drives. For the more advanced drive belt design refer to manufactures literature... I will include notes on these belt drives at a later date...

Designing a Synchronous Belt SystemBelt design procedures can be based on torque calculations or they can be based on power calculations.

Power method

1) The driven speed and the maximum driven torque required (including inertia load, shock loads, friction, etc) are used to calculate the required driven power

2) From information on the driver, driven equipment and operating period a service factor is obtained - see below

3) A design power is obtained based on the product of the Driven Power required and the service factor .

4) A belt section is initially selected using a graph as typically shown below

5) A drive geometry is derived selecting suitable pulleys, and belt Centre Distance - Some Pulley sizes are provided below

6) A Basic Power for the belt is calculated and a mesh factor is calculated - see below

7) A suitable belt width is selected -Using a table as provided below- Some iteration may be required

Torque MethodThe classical MXL belt and the Curvilinear more advanced belt options are designed based on torque levels.  The outline method for the MXL drive is provided below.    The method used for the HTD and other modern belt options will be provided at some future date...

The MXL belts operate generally at relatively low belt speeds so the torque levels are similar for the normal range of pulley rotational speed.  Torque ratings can be calculated of each of the MXL belt widths as follows: I have converted an imperial formula to a metric formula and minor differences with the original formulae results..

Torque ratings of belts Tr (Nm) at P2 PCDs (mm)

Belt width =3.048 mm... Tr = P2(5,03 - 9,5147.10-6.P22).10-3

Belt width =4.826mm... Tr = P2(8,36 - 1,586.10-5.P22).10-3

Belt width =6.35 mm...Tr = P2(11,7 - 2,213.10-5.P22).10-3

To design an MXL belt system using the torque method.

1) The driven speed and the maximum driven torque required (including inertia load, shock loads, friction, etc) are calculated

2) From information on the driver, driven equipment and operating period a service factor is obtained - see below

3) A design torque is obtained based on the product of the torque required and the service factor .

4) A belt section is initially selected (assuming MXL) using a graph as typically shown below

5) A drive geometry is derived selecting suitable pulleys, and belt Centre Distance - Some Pulley sizes are provided below

6) The design torque is divided by the teeth mesh factor (see below) to arrive at an adjusted torque

7) The table below is used to select the belt width which has a torque value equal to or larger than the corrected torque

  Torque Rating for MXL Belt (Nm)

No Teeth -> 10MXL 12MXL 14MXL 16MXL 18MXL 20MXL 22MXL 24MXL 28MXL 30MXL

PCD(mm) -> 6.477 7.7724 9.0678 10.3378 11.6332 12.9286 14.224 15.5194 18.1102 19.4056

width =3.05mm 0.033 0.040 0.045 0.052 0.059 0.064 0.071 0.078 0.092 0.097

width = 4.83mm 0.054 0.066 0.076 0.087 0.097 0.108 0.119 0.130 0.151 0.163

width = 6.35mm 0.076 0.090 0.106 0.121 0.136 0.151 0.166 0.182 0.211 0.227

Service FactorsWhen designing belt drives it is normal to apply a service factor to the drive operating load to compensate for allow for different driver type, driven load types and operating periods.  Typical service factor values are included on the linked page Service Factors

Designating Classical Synchronous beltsSynchronous Belt sizes are identified by a standard number.   The first digits specify the belt length to one-tenth inch followed by the belt section (pitch) designation.   The digits following the belt section designation represent the nominal belt width times 100.   For example, an L section belt 30.000 inches pitch length and 0.75 inches in width would be specified as a 300L075 Synchronous Belt.  A similar method is used for designating metric belt designations

Initial selection of Timing Belt When the design power has been determined (Power x Service Factor) a synchronous belt can be selected generally using a graph similar to the one below..This is provided for guidance only and is copied from published graphs generally available.

Horsepower Rating of Timing Belt This method is based on the method shown in Machinery's handbook.  It is preferable to use the calculation tool provided by the belt manufacturers to size the belts for detail design.   Or even better let the suppliers do the design for you...

The Power ratings of belts for the basic belt widths (in brackets) are as identified below.. r = Rpm of faster shaft /1000 P2 = Pitch diameter of smallest Pulley (mm) Z = P2.r /25.4

For Belt (width) = XL (9.652)...... Pr = 0.746.Z.(0,0916 - 7,07.10-5.Z2 )For Belt (width) = L (25,4)...... Pr = 0.746.Z.(0,436 - 3,01.10-4.Z2 )For Belt (width) = H (76,2)...... Pr =0.746.Z.(3,73- 1,41.10-3.Z2 )For Belt (width) = XH (101,6)...... Pr = 0.746.Z.(7,21 - 4,68.10-3.Z2 )For Belt (width) = XXH (127)...... Pr =0.746.Z.(11,14 - 7,81.10-3.Z2 )

Determining the timing belt length

1) The Pitch dia of a pulley P = No Teeth on Pulley . Pitch / 2) The Drop distance d = [ P1 - P2 ] /2

3) The belt contact angle α = arcsin(d /C) ..C= Centre distance4) The belt fall length = fl = d / tan α5) The contact length Small Pulley= CL2= P2. . [90 - α]/180 degrees6) The contact length Large Pulley = CL1=P1.. [90 + α]/180 degrees7) The Belt Length L = (2.fl) + 2.CL1 + 2.CL1

8) Total number of teeth on belt = L / Pitch9) Number of teeth in mesh (small pulley) = CL2 /Pitch. Rounded down to nearest whole number.

Mesh FactorThe horsepower ratings obtained above are based on the smallest pulleys having six or more teeth in mesh. For drives with small angles of lap on the smallest pulleys the mesh factor is required.

No Teeth in mesh

Mesh Factor

6 or more 1

5 0,8

4 0,6

3 0,4

2 0,2

Determination of the Belt Width required 1) First establish the design power to be transferred(kW) = Service Factor x Power.2) Select a suitable belt and calculate the basic power using the belt size, smaller pulley speed, and smaller pulley size.3) If the basic belt power is less than the design power- change one or more of belt size , pulley size or speed.3) Divide the Basic power/ Design power to obtain a belt width factor.4) Use the table below and select a width with a width factor higher than the calculated width factor required

Table of Belt Width Factors

Belt Sectio

n

Belt Width

3,05

4,826

6,35

9,652

12,7

19,05

25,4

38,1

50.8

76,2

101,6 127

MXL 0,43

0,731,00-

- - - - - - - - -

XL - - 0,62 1,00 - - - - - - - -

L - - - -0,45

0,721,00

- - - - -

H - - - - - 0,210,29

0,45

0,63

1,00

- -

XH - - - - - - - - 0,45

0,72

1,00 -

XXH - - - - - - - - 0,35

0,56

0,781,00

Typical Pulley Sizes

Below are listed a collection of pulley Dimensions (PCD and OD) for pulleys in the classical timing belt range.   In practice there are a vast number of pulleys available from suppliers on the belt sections shown and on other higher specification sections.   Additional data is available using the links below and preferable by contacting the suppliers.

MXL XL L H XH XXH

Teeth PCD OD Teeth PCD OD Teeth PCD OD Teeth PCD OD Teeth PCD OD Teeth PCD OD

10 6,47 5,96 10 16,17 15,67 10 30,32 29,56 10 40,43 39,08 18 127,34 124,54 18 181,91 178,87

11 7,11 6,61 11 17,79 17,29 11 33,35 32,59 11 44,47 43,12 20 141,49 138,68 20 202,13 199,09

12 7,76 7,25 12 19,40 18,90 12 36,38 35,62 12 48,51 47,16 22 155,64 152,83 23 232,45 219,30

14 9,06 8,55 13 21,02 20,52 13 39,41 38,65 13 52,55 51,20 24 169,79 167,01 25 252,66 239,50

16 10,35 9,84 14 22,64 22,14 14 42,45 41,68 14 56,60 55,25 26 183,94 181,15 26 262,76 259,72

18 11,64 11,13 15 24,26 23,76 16 48,51 44,72 15 60,64 59,29 28 198,08 195,30 30 303,19 300,15

20 12,94 11,78 16 25,87 25,37 17 51,54 47,75 16 64,68 63,33 30 212,23 209,45 34 343,62 340,56

21 13,58 13,07 17 27,49 26,99 18 54,57 50,78 17 68,72 67,37 32 226,38 223,60 40 404,25 401,19

22 14,23 13,72 18 29,11 28,61 19 57,61 56,84 18 72,77 71,42 40 282,98 280,19 48 485,10 482,07

24 15,52 15,02 20 32,34 31,84 20 60,64 59,88 19 76,81 75,46 48 339,57 336,78 60 606,38 603,32

28 18,11 17,60 21 33,96 33,46 21 63,67 62,91 20 80,85 79,50 60 424,47 421,67 72 727,66 648,41

30 19,40 18,90 22 35,57 35,07 22 66,70 65,94 21 84,99 83,54 72 509,36 506,58 90 909,57 906,53

32 20,70 20,19 24 38,81 38,31 24 72,77 72,00 23 92,98 91,63 84 594,25 591,46      

36 23,29 22,78 25 40,43 39,93 25 75,80 75,04 25 101,06 99,71 90 636,70 0,00      

40 25,87 25,37 26 42,04 41,54 26 78,83 78,07 26 105,11 103,76 96 679,15 676,35      

42 27,17 26,67 28 45,28 44,78 28 84,89 84,13 28 113,19 111,84 120 848,93 846,15      

44 28,46 27,94 30 48,51 48,01 30 90,96 90,19 30 121,28 119,93            

48 31,05 30,53 32 51,74 51,24 32 97,02 96,26 32 129,36 128,01            

60 38,81 38,30 36 58,21 57,71 36 109,15 108,39 33 133,40 132,05            

72 46,57 46,05 40 64,68 64,18 40 121,28 120,51 34 137,45 136,10            

      42 67,91 67,41 42 127,34 126,58 35 141,49 140,14            

      44 71,15 70,65 44 133,40 132,64 36 145,53 144,18            

      48 77,62 77,12 48 145,53 144,77 38 153,62 152,27            

      50 80,85 80,35 50 151,60 150,83 40 161,70 160,35            

      54 87,32 86,82 54 163,72 162,96 42 169,79 168,44            

      60 97,02 90,52 60 181,91 181,15 44 177,87 176,52            

      72 116,43 115,93 72 218,30 220,57 48 194,04 192,69