classification,advantages and disadvantages

1. BELT DRIVE
BY
• IMMANUEL
ALEXANDER(9203)

2. INTRODUCTION
 A belt is a looped strip of flexible material, used
to mechanically link two or more rotating
shafts.
 They may be used as a source of motion, to
efficiently transmit power, or to track relative
movement. Belts are looped over pulleys.
 In a two pulley system, the belt can either drive
the pulleys in the same direction, or the belt
may be crossed, so that the direction of the
shafts is opposite.

3. OVERVIEW WHY USED?
 Transfer power (torque) from one location to
another. From driver: motor,peddles,
engine,windmill,turbine to driven: conveyor
belt, back wheels/bike,generator rock
crusher,dryer.
 Used to span large distances or need flexible
x-mission elements. Gear drives have a
higher torque capability but not flexible or
cheap.
 Often used as torque increaser (speed
reducer), max speed ratio: 3.5:1. Gear
drives?? Virtually unlimited!

4. BELT DRIVE
ARRANGEMENTS
 Machines operated by belt drives must have an idler, an
adjustable base, or both
 Idler is use to help maintain constant tension on the belt
 Slack side: top side of belt in horizontal arrangement
 Tight side: bottom side of belt in horizontal arrangement
 Inside idler pulley is placed near the driver on the slack
side or on the tight side near the driven pulley
 Idler pulley should be same diameter or larger than the
driver
 Outside idler pulley is placed near the driver on the
outside of the belt on the slack side or on the tight side
near the driven pulley
 Idler pulley should be slightly larger than the driver pulley

5. TYPES
 FLAT BELT
 ROUND BELT
 VEE BELT
 MULTI-GROOVE BELT
 TIMING BELT

6. FLAT BELT DRIVE
 Flat belts for power transmission Flat belts:
 Advantages-Simple construction Low cost High
flexibility High tolerance to overload Good
resistance in abrasive environments
 Disadvantages-Noisy Sliding is possible Low
efficiency at low speeds Tensioning is required
 But these drives are bulky, requiring high tension
leading to high loads, and are poorly suited to
close-centers applications.
 Flat belts were traditionally made of leather or
fabric. Today some are made of rubber or
polymers. Grip of leather belts is often better if
they are assembled with the hair side (outer side)
of the leather against the pulley

7. USES/ADVANTAGES
 where high-speed applications (up to 140,000
rpm) are more important than power
transmission
 long center distances are necessary
 where drives with non-parallel shafts are
required (belt can be twisted)
 applications requiring small pulley diameters
(as small as 3/8")

8. DISADVANTAGE
 tend to slip under load
 lower efficiency at moderate speeds
 must be kept under tension to function (require
tensioning devices); causes high bearing loads
 require friction for proper functioning
(therefore, cannot be used when absolute
synchronization between pulleys must be
maintained)
 stretch over time

9. FLAT BELT

10. ROUND BELT DRIVE
 Round belts are a circular cross section belt
designed to run in a pulley with a 60 degree V-
groove.
 Round grooves are only suitable for idler
pulleys that guide the belt, or when (soft) O-
ring type belts are used.
 Early sewing machine utilized a leather belt,
joined either by a metal staple or glued, to
great effect.

11. ROUND BELTS

12. VEE BELT DRIVE
 They provide the best combination of traction,
speed of movement, load of the bearings, and long
service life.
 . The "V" shape of the belt tracks in a mating
groove in the Pulley (or sheave), with the result
that the belt cannot slip off. 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.

13. USES/ADVANTAGES
 Useful in automotive, household, industrial, and
agricultural applications
 easy to install and replace
 low maintenance
 provide shock absorption between driver and driven
shafts
 best at speeds between 1500 to 6500 feet per minute
(with 4500 fpm peak capacity, or ideal speed)
 useful with temperature range of –30 F to 180 F
 are 90-98% efficient
 maximum satisfactory speed ratio is approximately 6:1

14. DISADVANTAGE
 improper belt tension can reduce service life
 belt life at increased temperatures (above 180
F) is significantly shorted
 require friction for proper functioning

15. VEE BELT

16. MULTI GROOVE BELT DRIVE
 A multi-groove or polygroove belt is made up of
usually 5 or 6 "V" shapes alongside each other.
 This gives a thinner belt for the same drive surface
 offers an improved efficiency, as less energy is
wasted in the internal friction of continually
bending the belt.
 this gain of efficiency causes a reduced heating
effect on the belt and a cooler-running belt lasts
longer in service.

17. MULTIGROOVE BELT

18. TIMING BELT DRIVE
 Timing belt 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.
 Timing belts need the least tension of all belts,
and are among the most efficient.

19. USES/ADVANTAGES
 useful in operations requiring high efficiency,
timing or constant velocity
 no slippage (more positive power
transmission)
 will not stretch
 required belt tension is very low
 speed is transmitted uniformly

20. DISADVANTAGE
 shorter center distance required than flat belts
 used on parallel shafts only
 cost

21. TIMMING BELT

22. ADVANTAGES OF BELT DRIVE
 They are simple. They are economical.
 Parallel shafts are not required.
 Overload and jam protection are provided.
 Noise and vibration are damped out. Machinery
life is prolonged because load fluctuations are
cushioned (shock-absorbed).
 They are lubrication-free. They require only low
maintenance.
 They are highly efficient (90–98%, usually 95%).
Some misalignment is tolerable.
 They are very economical when shafts are
separated by large distances.

23.  Up to 95% efficient
 Designed to slip when an overload occurs
 Resist abrasion
 Require no lubrication (no metal to metal
contact)
 Smooth running
 Quiet
 Can transmit motion and power over long
distances

24.  Operate effectively at high speeds
 Flexible shaft center distances
 Inexpensive (when compared to other drive
systems such as chain or gear drives)
 Easy to assemble and install
 Have flexible tolerances
 Absorb shock well
 Easy and inexpensive to maintain

25. DISADVANTAGES OF BELT
DRIVE
 The angular-velocity ratio is not necessarily
constant or equal to the ratio of pulley diameters,
because of belt slip and stretch.
 Heat buildup occurs. Speed is limited to usually
7000 feet per minute (35 meters per second).
Power transmission is limited to 370 kilowatts (500
horsepower).
 Operating temperatures are usually restricted to –
31 to 185°F (–35 to 85°C).
 Some adjustment of center distance or use of an
idler pulley is necessary for wear and stretch
compensation.
 A means of disassembly must be provided to
install endless belts.