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Belts and Pulleys
Bel
ts a
nd P
ulle
ys
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 [email protected] +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 [email protected] +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 [email protected] +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 [email protected] +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 [email protected] +44 (0) 1484 601002 www.reliance.co.uk
Tech
nica
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 [email protected] +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