Design of Machine Elements: (Project Based Lab) Design Project:1 Belt Drives
Design of Machine Elements: (Project Based Lab) Design Project:1 Belt Drives
Design of Machine Elements: (Project Based Lab) Design Project:1 Belt Drives
CONTENTS
01 Introduction 03
02 Types of Belts 04
03 Parameters 09
(01) Alignment
(02) Tension
05 Applications 17
06 Selected Application 23
(01) Flat Belt
(02) V- Belt
INTRODUCTION
Power transmission belting has been used for more than 200 years. The first belts were flat and ran on
flat pulleys. Later, cotton or hemp rope was used with V-groove pulleys to reduce belt tension. This led
to the development of the vulcanized rubber V-belt in 1917. The need to eliminate speed variations led
to the development of synchronous or toothed belts about 1950 and the later.
Power transmission belting has been used for more than 200 years. The first belts were flat and
ran on flat pulleys. Later, cotton or hemp rope was used with V-groove pulleys to reduce belt
tension. This led to the development of the vulcanized rubber V-belt in 1917. The need to
eliminate speed variations led to the development of synchronous or toothed belts about 1950
and the later development of fabric-reinforced elastic materials.
Today, flat, V, and synchronous belting is still being used in power transmission. When
compared to other forms of power transmission, belts provide a good combination of flexibility,
low cost, simple installation and maintenance, and minimal space requirements.
Belt-driven equipment uses readily available components. Replacement parts can be easily
obtained from local distributors. This availability reduces downtime and inventory. Sheaves and
pulleys are usually less expensive than chain drive sprockets and have little wear over long
periods of operation.
Types of Belts
All power transmission belts are either friction drive or positive drive. Friction drive belts rely on
the friction between the belt and pulley to transmit power. They require tension to maintain the
right amount of friction. Flat belts are the purest form of friction drive while V-belts have a
friction multiplying effect because of wedging action on the pulley.
Positive drive or synchronous belts rely on the engagement of teeth on the belt with grooves on
the pulley. There is no slip with this belt except for ratcheting or tooth jumping.
Fig. 1. Flat belts have thin cross-sections and wrap around pulleys easily
A significant advantage of flat belts is efficiency of nearly 99%, about 2.5-3% better than V-
belts. Good efficiency is due to lower bending losses from a thin cross-section, low creep
because of friction covers and high modulus of elasticity traction layers, and no wedging action
into pulleys.
Pulley alignment is important to flat belts. Belt tracking is improved by crowning at least one
pulley, usually the larger one. Flat belts are forgiving of misalignment; however, proper
alignment improves belt life.
Different flat belt surface patterns serve various transmission requirements. In high-horsepower
applications and outdoor installations, longitudinal grooves in the belt surface reduce the air
cushion flat belts generate. The air cushion reduces friction between the pulley and belt. The
grooves nearly eliminate the effects of dirt, dust, oil, and grease and help reduce the noise level.
Flat belts operate most efficiently on drives with speeds above 3000 fpm. Continuous, smooth-
running applications are preferred. Speed ratios usually should not exceed 6:1. At higher ratios,
longer center distances or idlers placed on the slack side of the belt create more wrap around the
smaller pulley to transmit the required load.
(02) V-belts
V-belts are commonly used in industrial applications because of their relative low cost, ease of
installation, and wide range of sizes (Fig. 2). The V-shape makes it easier to keep fast-moving
belts in sheave grooves than it is to keep a flat belt on a pulley. The biggest operational
advantage of a V-belt is the wedging action into the sheave groove. This geometry multiplies the
low tensioning force to increase friction force on the pulley sidewalls (Fig. 3).
Fig. 3.
Classical V-belts are frequently used individually, particularly in A and B sizes. The larger C, D,
and E sizes generally are not used in single-belt drives because of cost penalties and
inefficiencies. Multiple A or B belts are economical alternatives to using single-belt C, D, or E
sections.
Narrow V-belts, for a given width, offer higher power ratings than conventional V-belts. They
have a greater depth-to-width ratio, placing more of the sheave under the reinforcing cord. These
belts are suited for severe duty applications, including shock and high starting loads.
Banded V-belts solve problems conventional multiple V-belt drives have with pulsating loads.
The intermittent forces can induce a whipping action in multiple-belt systems, sometimes
causing belts to turn over. The joined configuration avoids the need to order multiple belts as
matched sets.
Banded V-belts should not be mounted on deep-groove sheaves, which are used to avoid
turnover in standard V-belts. Such sheaves have the potential for cutting the band of joined belts.
Extremely worn sheaves produce the same result.
V-ribbed belts combine some of the best features of flat belts and V-belts. The thin belt operates
efficiently and can run at high speeds. Tensioning requirements are about 20% higher than V-
belts. The ribs ensure the belt tracks properly, making alignment less critical than it is for flat
belts.
The first tooth profile used on synchronous belts was the trapezoidal shape (Fig. 4). It is still
recognized as standard. Recent modifications to tooth profiles have improved on the original
shape. The full-rounded profile distributes tooth loads better to the belt tension members. It also
provides greater tooth shear strength for improved load capacity.
A modified curvilinear tooth design has a different pressure angle, tooth depth, and materials for
improved load/life capacity and non-ratcheting resistance.
Synchronous belts can wear rapidly if pulleys are not aligned properly, especially in long-center-
distance drives, where belts tend to rub against pulley flanges. To prevent the belt from riding off
the pulleys, one of them is usually flanged. A recent development has produced a belt and pulley
that use a V-shaped, instead of straight, tooth shape. It runs quieter than the other shapes and
doesn't require pulley flanges.
Under tensioning causes performance problems. The drive may be noisy because belt teeth do
not mate properly with pulley grooves or the belt may prematurely wear from ratcheting. High
forces generated during belt ratcheting are transmitted directly to shafts and bearings and can
cause damage.
These belts can transmit the same horsepower as classic V-belts. The links are made of plies of
polyester fabric and polyurethane that resist heat, oil, water, and many chemicals.
Advantages of link belts include quickly making up matched sets, fast installation because
machinery doesn't have to be disassembled, and vibration dampening.
Disadvantages include cost and the possible generation of static charges. The belt should be
grounded when used in high-dust applications.
PARAMETERS
(01) ALIGNMENT
Misalignment is one of the most common causes of premature belt failure (Fig. 6). The problem
gradually reduces belt performance by increasing wear and fatigue. Depending on severity,
misalignment can destroy a belt in a matter of hours. Sheave misalignment on V-belt drives
should not exceed 1/2 deg. or 1/10 -in. of center distance. For synchronous belts it should not
exceed 1/4 deg. or 1/16-in. of center distance.
Fig. 6. Improper drive maintenance is the biggest source of belt drive problems
Angular misalignment (Fig. 7) results in accelerated belt/sheave wear and potential stability
problems with individual V-belts. A related problem, uneven belt and cord loading, results in
unequal load sharing with multiple belt drives and leads to premature failure.
Angular misalignment has a severe effect on synchronous belt drives. Symptoms such as high
belt tracking forces, uneven tooth/land wear, edge wear, high noise levels, and potential failure
due to uneven cord loading are possible. Wide belts are more sensitive to angular misalignment
than narrow belts.
Parallel misalignment also results in accelerated belt/sheave wear and potential stability
problems with individual belts. Uneven belt and cord loading is not as significant a concern as
with angular misalignment.
Parallel misalignment is typically more of a concern with V-belts. They run in fixed grooves and
cannot free float between flanges to a limited degree as synchronous belts can. Parallel
misalignment is generally not a critical concern with synchronous belts as long as the belt is not
trapped or pinched between opposite sprocket flanges and tracks completely on both sprockets.
(02) Tension
Total tension required in a belt drive depends on the type of belt, the design horsepower, and the
drive rpm. Since running tensions cannot be measured, it is necessary to tension a drive
statically.
The force/deflection method is most often used. Once a calculated force is applied to the center
of a belt span to obtain a known deflection, the recommended static tension is established. Most
design catalogs provide force and deflection formulas.
With too little tension in a V-belt drive, slippage can occur and lead to spin burns, cover wear,
overheating of the belt, and possibly overheating of bearings. Not enough tension in a
synchronous belt causes premature tooth wear or possible ratcheting that will destroy the belt and
could break a shaft.
When installing a new belt, installation tension should be set higher. Generally, 1.4-1.5 times the
normal static tension. This is necessary because drive tension drops rapidly during the seating-in
process. This extra initial tension does not affect bearings because it decays rapidly.
V-ribbed
Application Synchronous belt V-belt
belt
Speed/Load
High speed 2 2 1 1
Low speed 1 1 2 3
High load 1 2 4 3 3
Low load 1 2 3 4 4
Shock/impulse load 3 4 1 2
Serpentine drive 1
Serpentine drive w/
2
shock load
Twisted drive 1 2 3
Clutching drive 1 2
Drive characteristics
Reversing direction 1 1 3 4 2
Frequent start/stop 1 1 3 4 2
Smooth running 3 2 1 1
Variable speed 1
Oil, chemical
1 3 4 2
environment
High temperature 1 2 4 4 3
Low temperature 1 2 3 4
1=First choice, 4=Last choice Chart Courtesy The Gates Rubber Co.
Belt sidewalls soft and Remove source of oil or grease. Clean belts
sticky. Low adhesion Oil or grease contamination of and sheave grooves cloth moistened with
between cover, plies. belt/sheave nonflammable, non-toxic degreasing agent or
Cross section swollen commercial detergent and water
Bottom of belt cracked Sheaves too small Redesign drive for larger sheaves
Belt turnover
Tensile member broken from Replace belts with new, matched set,
improper installation properly installed
Belt noise
Incorrect driver/driven
Design error Change sheaves
ratio
Hot bearings
Motor/belt manufacturer's
Sheaves too small recommendations not Redesign drive
followed
8000—25,000
sdp-si.com Synchronous 0.01—18 149.6
rpm
2000—20,000
Flat 0.04—0.2 19.7
rpm
APPLICATIONS
(01) Conveying
Industrial conveyors are horizontal, inclined, declined,
or vertical
machines which move materials from one place to
another at a
controlled rate.
Applications
• Packaging Equipment Glass Processing
• Low Profile Conveyors
• Small Part Transfer
• Hygiene Product Machines
• High Speed Conveying
• Rapid Indexing
• Vacuum Applications
• Automated Process Conveyors
• Bulk Product Conveying
• Food & Confectionery Conveying
• Glass Processing
• Medical Equipment
• Paper/Paperboard Manufacturing
• Pharmaceutical Box Folding
• Printing
Applications
• Linear Actuators
• Automatic Door
• Automated Storage and Retrieval
• Woodworking
• Glass Fabrication
• Medical Equipment Automatic Doors
Applications
• Food
• Medical Equipment
• Packaging
• Textiles
(04) Lifting
Transmission systems that are driven by flat belts.
Flat Lifting Belts - F8, FL8, F12, FL12, F30, FX9, FX12, F13, F19
Applications
• Automotive
• Elevator
Elevators
Food Processing
Choosing the right conveyor belt for your product is one of the most important, and often over-
looked, details in the selection of a conveyor. The type of material the belt is made of is vital to
the success of the application, and having the wrong belt can significantly affect throughput,
downtime and safety.
There are many different types of belts available so the first step in choosing the correct belt is to
know your product and how it will convey. Several key points to consider are:
Once you have a good understanding of your product and the environment it will operate in, you
can select the proper belt. Below are the basic belt types available. (This is not by any means an
exhaustive list. There are many other specialty belts available.)
This wide group of belting is typically made of an inner carcass and an outer cover. The
materials used for these belts include rubber, PVC, Urethane, Neoprene, Nylon, Nitrile,
Polyester, leather and others.
Common industry names for this type of belting include: Table Top, Mat Top, Angled Roller
Belting, and Micro Span. It is often lightweight, durable and wear resistant.
• Food production
• Packaging
• Pharmaceuticals
• Manufacturing
Hinge metal belting is incredibly durable is often used for machine chip and scrap removal.
• Packaging operation
• Inspection
• Stamping operation
Woven wire belting is commonly used in very high/low temperature environments and during
the drying process. Below are some of its many applications.
As its name suggests, flat wire belting has a flat surface making it ideal for food handling. It is
more economical at time compared to woven wire belting.
Once you have selected the appropriate type of belt, be sure to also consider the specifics of how
the belt can be cleaned and maintained, replaced or modified, and the costs associated with these.
Again, this is not intended to be a complete list of conveyors belting, but is a guide to the most
common types used in the industry today. If you have questions about which type of conveyor
belt is right for your application, please contact me anytime.
SELECTED APPLICATION
(01) Flat Belt
Belt Conveyor system – Light Industry
Specifications
• Usage: Material Transmission
• Belt Material: PVC
• Power: 18 kW
• Center Distance: 03 m
• Velocity: 18 m/s
• Speed: 1440 rpm
• Speed Ratio: 2:1
Flat Belt Drive
Inputs
Power(kW) 18
speed (smaller pulley) n1(rpm) 1440
Speed Ratio 0.5
velocity(m/s) 18 (Assumption)
Load Correction Factor 1.2 From Table
Center Distance(mm) 3000
Calculations
Actual Power Transmitted 15
Diameter of smaller Pulley(d)(mm) 238.8535032 Selecting Preferred Pulley Diameter
d(mm) 250
Diameter of bigger Pulley(D)(mm) 500
Corrected Velocity (m/s) 18.84
Angle of wrap 178.7875399
Arc contact Factor (fd) 1.00484984
Corrected Power (kw) 14.92760351
No of Belts 1.205819808 (Approximately 2)
Length of Belts(mm) 6790.208333
(02) V-Belt:
Centrifugal Pump
Specifications
• Usage: Power Transmission
• Belt Material: PVC
• Power: 3.68 kW
• Center Distance: 0.770 m
• Velocity: 18 m/s
• Speed: 1440 rpm
• Speed Ratio: 1.44:1
V- Belt Drive
Inputs
Power(kW) 3.68
speed (smaller pulley) n1(rpm) 1440
Speed Ratio 0.69
velocity(m/s) 18
Service Factor 1 From Table
Center Distance(mm) 770
Correction factor 1.02 From Table
Pr 5.9 From Table
Arc contact Factor (fd) 0.98 From Table
Calculations
Actual Power Transmitted 3.68
Diameter of smaller Pulley(d)(mm) 238.8535032 Selecting Preferred Pulley Diameter
d(mm) 250
Diameter of bigger Pulley(D)(mm) 362.3188406
Corrected Velocity (m/s) 18.84
Angle of wrap 178.0902412
Corrected Power (kw) 3.755102041
No of Belts 0.623978405 (Approximately 1)
Length of belt(mm) 2112.936528