Belts and Pulleys

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10

Section Contents

Timing Belts 2.5mm Pitch ........................................................Page 10­2

Timing Pulleys 2.5mm Pitch ....................................................Page 10­3

Timing Belts 5mm Pitch ............................................................Page 10­4

Timing Pulleys 5mm Pitch ........................................................Page 10­5

Technical Information................................................................Page T10­1

10­2 Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

Belts andPulleys

Associated ProductsTiming pulleys: page 10­3

All dimensions in mmMaterial: High tensile steelreinforced polyurethane

Part number selection table

Example Part No:­ TXM25 F6­ 168

BasicPart

Number

BeltWidth

Standard Lengths#

Number ofPitches

Lengthmm

Number ofPitches

Lengthmm

TXM25 6 mmF6­

485864717273809298

106114116

120.0145.0160.0177.5180.0182.5200.0230.0245.0265.0285.0290.0

127132152168192200240248260312380

317.5330.0380.0420.0480.0500.0600.0620.0650.0780.0950.0

Features and options Technical support• Temperature range: ­10°C to +80°C• Maximum allowable peripheral load:

6 mm wide = 65 N• Maximum peripheral speed: 80 m/s• Special polyurethanes available• Double­sided belt available• Alternative lengths available#

• Alternative colours available• Kevlar tension members available• Anti­static belts available

• Technical information ­ see page T10­1• Design guidelines ­ see page T10­2

2.5mm Pitch Timing Belts

# The belt thickness may differ if a non­standard length is ordered

2.5mm Pitch

10­3

Timing Pulleys

Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

Bel

ts a

ndPu

lleys

All dimensions in mmMaterials: Aluminium alloy

pulley with zinc platedsteel flanges

Associated ProductsIntelligent motors: page 2­2Shafts: page 11­2Timing belts: page 10­2

Part number selection table

Example Part No:­ TPMP25 F6­ 60

Basic PartNumber

BeltWidth

No. ofTeeth

PitchDiameter

BoreØB (H8)

Hub DiameterØH ±1.0

TPMP25 6 mmF6­

12141518192024253032364048*60*

9.5511.1411.9414.3215.1215.9219.1019.8923.8725.4628.6531.8338.2047.75

31315151010111213161620222634

4

6

8*Pulleys with 48 and 60 teeth are unflanged

When belt width = 6, W=10 & L=16

Features and options Technical support• Zero­backlash pulleys• Other numbers of teeth available• 0, 1 or 2 flanges available• Tapped holes in hubs available• Alternative bore diameters available• Alternative mountings available• Keyed bores available

• Technical information ­ see page T10­1• Design guidelines ­ see page T10­2

10­4 Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

Belts andPulleys

Associated ProductsTiming pulleys: page 10­5

All dimensions in mmMaterial: High tensile steelreinforced polyurethane

Part number selection table

Example Part No:­ TXM50 F10­ 168

BasicPart

Number

BeltWidth

Standard Lengths#

Number ofPitches

Lengthmm

Number ofPitches

Lengthmm

Number ofPitches

Lengthmm

TXM50

10 mmF10­

or

16 mmF16­

203033363740424345495052545659

100150165180185200210215225245250260270280295

6668738082849196

100102105110115122124

330340365400410420455480500510525550575610620

126138140145150156163168180185188198215243276

630690700725750780815840900925940990

1,0751,2151,380

Features and options Technical support• Temperature range: ­10°C to +80°C• Maximum allowable peripheral load:

10 mm wide = 330 N, 16 mm wide = 570 N• Maximum peripheral speed: 80 m/s• Special polyurethanes available• Double­sided belt available• Alternative lengths available#

• Alternative colours available• Kevlar tension members available• Anti­static belts available

• Technical information ­ see page T10­1• Design guidelines ­ see page T10­2

5mm Pitch Timing Belts

# The belt thickness may differ if a non­standard length is ordered

5mm Pitch

10­5

Timing Pulleys

Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

Bel

ts a

ndPu

lleys

All dimensions in mmMaterials:Aluminium alloy

pulley with zinc platedsteel flanges

Associated ProductsIntelligent motors: page 2­2Shafts: page 11­2Timing belts: page 10­4

Part number selection table

Example Part No:­ TPMP50 F10­ 60

Basic PartNumber

BeltWidth

No. ofTeeth

PitchDiameter

BoreØB (H8)

Hub DiameterØH ±1.0

TPMP50

10 mmF10­

or

16 mmF16­

10121415161819202425273032364048*60*

15.9219.1022.2823.8725.4628.6530.2431.8338.2039.7942.9747.7550.9357.3063.6676.3995.49

4

6

8

811131618202223262630343838405065

WhenWhen

belt width = 10, W=15 & L=21belt width = 16, W=21 & L=27

*Pulleys with 48 and 60 teeth are unflanged

Features and options Technical support• Zero­backlash pulleys• Other numbers of teeth available• 0, 1 or 2 flanges available• Tapped holes in hubs available• Alternative bore diameters available• Alternative mountings available• Keyed bores available

• Technical information ­ see page T10­1• Design guidelines ­ see page T10­2

TechnicalInformation

T10­1

Belts and Pulleys

Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

Tech

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lIn

form

atio

n

INTRODUCTION

Timing belts are endless toothed belt systems available in 2.5 mm and 5 mm pitch; intended forapplications requiring a level of power transmission.

ENGINEERING DATA

1. Belt and Chain LengthKnowing the centre distance, the belt length can be calculated from the following:

[mm]

[mm]

a = Centre distanceLB = Belt lengthd1 = Pitch diameter small pulleyZ1 = No of teeth, small pulleyZB = No of teeth in belt

t = Belt pitchd2 = Pitch circle diameter large pulleyZ2 = No of teeth, large pulleyZe = No of teeth in mesh

t

LB,ZBd1

Z2d2

Z1

a

(approximate formula)

TechnicalInformation Belts and Pulleys

T10­2 Contact us for product information, design support and custom solutionssales@reliance.co.uk +44 (0) 1484 601002 www.reliance.co.uk

TechnicalInform

ation

2. Centre Distance CalculationKnowing the belt length, the centre distance can be calculated from the following;

3. Design GuidelinesTiming belt efficiency ranges from 95 to 98%, better than flat vee belts which rely on friction totransmit power. The 2.5 mm and 5 mm pitch timing belts are manufactured in wear resistantpolyurethane with high grade steel wire tension members, therefore any elongation due to load andpre­tension will follow Hookes’ law. The manufacturing process for these timing belts produces the‘classical’ trapeziodal tooth form to close tolerances. This ensures an even distribution of load duringuse and the transmission of high torques. These belts are suitable for indexing, positioning andconveying drives.

It is possible to design drives with fixed centres but generally the drive centres should be adjustableor have idler pulleys. This is particularly important in multi­shaft or high power drives. The idler pulleysshould be fitted to the slack side of the drive and must not be spring loaded. Timing belt drives do notrequire as much tension as other belt drives which depend on friction to transmit load. The belt shouldbe installed with a snug fit, neither taut nor loose. As a general guide the correct level of tension canbe determined by measuring the force necessary to deflect the belt an amount equal to 1/64th of thespan centres “a”. Values for the measuring force recorded on a spring balance applied mid­spanshould be within 20% of the values shown below.

2.5 mm ­ 0.07kg 5 mm ­ 0.30kg

The belts must be rigidly mounted. Variation in centre distance can lead to premature wear. The beltand pulley system must be assembled loose to prevent over stretching. The belts are guided on thepulleys by flanges. One pulley should be flanged on both sides, or two alternative flanges provided,one on each pulley. For drives with vertical shafts, both pulleys should be flanged on both sides.

For a belt to transmit full power, a minimum of 6 teeth must be in mesh on each pulley.The number of teeth in mesh can be determined from the following formula:

To minimise belt fatigue, pulleys with a minimum of 20 teeth are recommended. As a general guidelarger pulleys reduce the amount of belt flexing and therefore improve belt life.

Number of teeth in meshcalculation is always basedon the smallest pulley.

arc cosZe180

[mm]

[mm]

(approximate formula)

[mm] [mm]

RG36 Issue A2