2. WHAT IS A BELT…??
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. Belts are looped over pulleys and may have a
twist between the pulleys, and the shafts need not be parallel. The
main function of a belt is power transmission.
3. POWER TRANSMISSION
Belts are the cheapest utility for power transmission between shafts
that may not be axially aligned. Power transmission is achieved by
specially designed belts and pulleys. The demands on a belt drive
transmission system are large and this has led to many variations on
the theme. They run smoothly and with little noise, and cushion motor
and bearings against load changes, albeit with less strength than
gears or chains. However, improvements in belt engineering allow use
of belts in systems that only formerly allowed chains or gears.
4. ADVANTAGES AND DISAVANTAGES
ADVANTAGES:-
Cheap
Works on non axial shafts
Noise and vibration free
No lubrication needed
High efficiency
High tolerance to misalignment
Different speeds can be obtained
DISADVANTAGES:-
Angular velocity keeps on changing
The work in a particular temperature
range
They wear off easily
5. FACTORS TO BE CONSIDERED WHILE
DESIGNING BELTS
Shafts should be properly in line
Pulleys should neither be too close nor too far
Tight side of the belt should be at the bottom
Maximum distance should not exceed 10m
Minimum distance should not be less than 3.5 times the dia of larger pulley
6. SELECTION OF BELT DRIVES
The factors to be considered while selecting belt drives are:-
Speed of the driving and driven shafts
Power to be transmitted
Centre distance between the shafts
Space available
Service conditions
7. TYPES OF BELTS DRIVES
Light drives - They are used to transmit small power at belt speeds upto
10mps.
Medium drives - They are used to transmit medium power at belt speeds
between 10mps to 22mps.
Heavy drives - They are used to transmit large power at belt speeds
above 22mps.
8. TYPES OF BELTS
Flat belts
Round belts
V-belts
Multi-groove belt
Timing belt
9. FLAT BELTS
Flat belts are widely used in line shafting to transmit power in factories. They are
also used in countless farming, mining, and logging applications, such
as bucksaws, sawmills, threshers, silo blowers, conveyors for filling corn
cribs or haylofts, balers, water pumps and electrical generators. The flat belt is a
simple system of power transmission that was well suited for its daily usage. It can
deliver high power at high speeds (500 hp at 10,000 ft/min or 373 kW at 51 m/s),
in cases of wide belts and large pulleys.
10. V-BELT
V belts solved the slippage and alignment problem. It is now the basic belt for power
transmission. They provide the best combination of traction, speed of movement, load of the
bearings, and long service life. They are generally endless, and their general cross-section shape
is Roughly trapezoidal . The belt also tends to wedge into the groove as the load increases—the
greater the load, the greater the wedging action—improving torque transmission and making the
V-belt an effective solution, needing less width and tension than flat belts. V-belts trump flat belts
with their small center distances and high reduction ratios. The preferred center distance is larger
than the largest pulley diameter, but less than three times the sum of both pulleys. Optimal speed
range is 1,000–7,000 ft/min (300–2,130 m/min). V-belts need larger pulleys for their thicker cross-
section than flat belts.
11. TIMING BELTS
Timing belts are a positive transfer belt and can track relative movement. These belts have teeth
that fit into a matching toothed pulley. When correctly tensioned, they have no slippage, run at
constant speed, and are often used to transfer direct motion for indexing or timing purposes.
They are often used in lieu of chains or gears, so there is less noise and a lubrication bath is not
necessary. Camshafts of automobiles, miniature timing systems, and stepper motors often utilize
these belts. Timing belts need the least tension of all belts, and are among the most efficient. They
can bear up to 200 hp (150 kW) at speeds of 16,000 ft/min (4,900 m/min).