This document provides information about flat belt drives, including what they are, common materials used, types of flat belt drives, design considerations, and advantages/disadvantages. It begins with definitions of belt drives and flat belt drives. It then discusses materials, types of configurations (open, crossed, with idlers, compound), and selection criteria like shaft speeds and spacing. The document outlines the design process and provides equations for determining velocity, pulley sizes, arc of contact, tensions. It concludes with the advantages of flat belts being simple and durable but disadvantages like higher slippage risk compared to V-belts.

1. Design of Machine Element (2151907)
B.E. MECH – Sem Vth
Prepared by, .
Shreejit Nair (170953119020)
Chaitanya Pandya (170953119023)
Shrey Patel (170953119031)
Yogesh Rathva (170953119036)
Guided by,
Asst. Prof. Bharat G. Kumar
(Mechanical Deptt)
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2. CONTENTS
• What Is Belt Drive ?
• What Is Flat Belt Drive ?
• Belt Material
• Types Of Belt Drive
• Belt Drive Selection Criteria
• Design Of Flat Belt Drive
• Advantage Of Flat Belt Drive
• Disadvantage Of Flat Belt Drive
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3. WHAT IS BELT DRIVE?
• A belt is a loop of flexible material used to link two or more rotating shafts
mechanically, most often parallel. Belts may be used as a source of motion, to
transmit power efficiently or to track relative movement.
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4. WHAT IS FLAT BELT DRIVE?
• It is the belt of square or rectangle cross section used to transmit the power
between two shafts.
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5. BELT MATERIAL
• According to the Material Used Belts are classified into
1. Leather Belts
2. Cotton or Fabric Belts
3. Rubber Belts
4. Balata belts
Similar to rubber belt except that balata gum is used in place of rubber
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6. TYPES OF FLAT BELT DRIVE
• Open Belt Drive: The open belt drive is used with shafts arranged parallel and
rotating in the same direction.
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7. • Crossed Belt Drive: The crossed belt drive is used with shafts arranged
parallel and rotating in the opposite direction
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8. • Belt Drive with Idler pulleys: It is used with shafts arranged parallel and when
belt drive cannot be used due to small angle of contact on the smaller pulley.
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9. • Compound belt drive : A compound belt drive is as shown in fig. used to
transmit power from one shaft to another shaft through no. of pulleys.
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10. • Stepped or Cone pulley Drive: It is used for changing the speed of the driven
shaft while main shaft runs at constant speed.
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11. BELT DRIVE SELECTION CRITERIA
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• Speed of driving and driven shafts
• Power to be transmitted
• Positive Drive Requirements
• Space Available
• Speed Reduction Ratio
• Centre distance between two shaft
• Shaft layout
• Service Condition

12. DESIGN OF FLAT BELT DRIVE
• Step 1: To find velocity of drive.
𝑉 =
𝜋𝑑𝑛
60
Where,
V = Velocity
d = Diameter of smaller pulley
n = rpm of smaller pulley
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13. • Step 2 : Ratio of diameter and rpm.
𝑁
𝑛
=
𝑑
𝐷
Where,
N = rpm at lager pulley
D = Diameter at lager pulley
d = Diameter of smaller pulley
n = rpm at smaller pulley
• Step 3:Determine the arc of contact.
Arc of contact, 𝜃 = 180 −
𝐷−𝑑 60
𝐶
Where,
C=center distance
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14. • Step 5 : Find tension in tight side
T1 = Tmax - TC
Where,
Tmax = Max tension = σ × cross section area
TC = Centrifugal tension
TC =
𝑇 𝑚𝑎𝑥
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• Step 6 : Ratio of tension on tight side and slake side.
𝑇1
𝑇2
= 𝑒 𝜇𝜃
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15. • Step 7 : Find power transmitted by belt drive.
P = (T1 - T2) V
Where,
P = Power transmitted
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16. ADVANTAGES OF FLAT BELT DRIVE
• Flat belts are simple in design and cheaper.
• Smooth and quiet running.
• It can be used for long distance even up to 15m.
• They are durable.
• Precise alignment of shaft and pulley is not criteria.
• They are flexible.
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17. DISADVANTAGES OF FLAT BELT DRIVE
• High chance of slip off.
• It require more pretension compare to v-belt to transmit certain torque.
• Flat belts are not advisable for higher output at higher speed.
• They are bulky and require wide pulley.
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18. ANY QUESTION ?
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