Belt,rope,chain Drives 6m5d3y

INTRODUCTION TO BELTS,ROPE & CHAIN DRIVE

BELT  Used to transmit power from one shaft to another

by means of pulley.  The amount of power transmitted depends upon the following factor 1.Velocity of the belt 2.Tension under which belt is placed in pulley. 3.Condition under which belt is used.

CONDITION UNDER WHICH BELT IS USED  The shaft should be properly in line.

 The pulley should not be too close & too far to

avoid arc of , increasing friction load on the bearing .  The long belt tends to swing, causing the belt to run out of the pulley.  In flat belt the maximum distance between pulley not more than 10 m/s & minimum should be less than 3.5 times the diameter of the pulley.

SELECTION OF BELT DRIVE  Speed of the driving and follower shaft

 Speed reduction ratio  Power to be transmitted  Centre distance between the shaft  Space available  Service conditions

TYPES OF BELT DRIVE  LIGHT DRIVE: Transmit power at belt speed

10m/s ex. small machine tools.  MEDIUM DRIVE: Transmit power at belt speed between 10m/s to 22m/s  HEAVY DRIVES: Transmit power at belt speed above 22 m/s (ex) compressor, generator

TYPES OF BELT FLAT BELT

V BELT

CIRCULAR BELT OR ROPE

POWER

MODERATE AMOUNT OF POWER IS TO TRANSMITTED

MODERATE AMOUNT OF POWER IS TO TRANSMITTED

GREAT AMOUNT OF POWER IS TO BE TRANSMITED

DISTANCE

TWO PULLEYS ARE NOT MORE THAN THE 8 METERS APART

TWO PULLEYS ARE VERY NEAR TO EACH OTHER

TWO PULLEYS ARE MORE THAN THE 8 M/S APART

APPLICATION

WORK SHOP WORKSHOP WORKSHOP AND FACTORIES AND FACTORIES AND FACTORIES

MATERIALS USED FOR BELT LEATHER BELT

COTTON OR FABRIC RUBBER BELT BELT

BALATA BELTS

MADE FROM 1.2 MTS TO 1.5 MTS

MADE BY FOLDING CANVAS TO THREE OR MORE LAYER AND STICHING TOGETHER

MADE OF LAYERS IMPREGNATED WITH RUBBER COMPOSITION

BALATA GUM IS USED IN PLACE OF RUBBER

HAIR SIDE IS STRONGER THAN THE FLESH SIDE

IMPREGNATED WITH FILLER LIKE LINSEED OIL TO MAKE BELT WATER PROOF AND PREVENT INJURY TO FIBRES

THEY ARE FLEXIBLE BUT DESTROYED IF ALLOWED COME IN WITH HEAT,OIL,GREAS E

THEY ARE ACID PROOF AND WATER PROOF

HAIR SIDE SHOULD HAVE WITH PULLEY WHERE TENSION IS MAXIMUM

THEY ARE USED AS BELT CONVEYOR

SUTABLE FOR SAW MILLS AND PAPER MILLS

THIS BELT SHOULD NOT BE AT TEMPERATURE ABOVE 40°C

THE LEATHER MAY BE CHROME TANNED.

AT THIS TEMP.IT IS SOFTEN AND STICKY

TYPES OF FLAT BELT OPEN BELT

CROSSED OR TWIST

QUARTER TURN

DRIVE WITH IDLER PULLEY

SHAFT ARRANGED IN PARALLEL AND ROTATING IN SAME DIRECTION

SHAFT ARRANGED PARALLEL BUT ROTATING IN OPPOSITE DIRECTION

KNOWN AS RIGHT ANGLE BELT DRIVE,SHAT ARRANGED IN RIGHT ANGLE,ROTATING IN ONE DIRECTION

SHAFT ARRANGED IN PARALLEL,BELT CANNOT BE USED DUE TO SMALL ANGLE OF WITH PULLEY

DRIVER PULLS FROM ONE SIDE AND DELIVERS TO OTHER SIDE

DRIVER PULLS FROM ONE SIDE AND DELIVERS TO OTHER SIDE

TO PREVENT BELT FROM LEAVING PULLEY WIDTH OR FACE OF PULLEY GREATER OR EQUAL TO 1.4 B

USED TO OBTAIN HIGH VELOCITY RATIO,AND USED WHEN REQD HIGH TENSION IS NOT OBTAINED

THUS THE TENSION IN LOWER SIDE WILL BE MORE THAN UPPER SIDE

BELTS CROSS EACH OTHER WEAR AND TEAR OCCURS

THE LOWER SIDE IS KNOWN AS TIGHT SIDE AND UPPER SIDE AS SLACK SIDE

SHAFT SHOULD BE PLACED MAX DISTANCE 20B WHERE B IS WIDTH OF BELT AND SPEED OF SHOULD BE LESS

TYPES OF FLAT BELT COMPOUND BELT DRIVE

STEPPED OR CONE BELT

FAST AND LOOSE PULLEY

POWER IS TRANSMITTED FROM ONE SHAFT TO ANOTHER SHAFT THROUGH NUMBER OF PULLEY

CHANGE THE SPEED OF THE FOLLWER SHAFT WHILE DRIVER SHAFT IS RUNNING AT CONSTANT SPEED

IT IS USED WHEN THE FOLLOWER OR MACHINE SHAFT IS TO BE STARTED OR STOPPED WITHOUT INTERFERING THE DRIVING PULLEY

IT IS ACOMPLISHED BY SHIFTING THE BELT FROM ONE PART OF STEP TO OTHER

IN THIS CASE THE PULLEY KEYED WITH MACHINE SHAFT IS CALLED FAST PULLEY AND LOOSE PULLEY RUNS FREELY OVER THE MACHINE WITHOUT TRANSMITING POWER

VELOCITY RATIO OF BELT DRIVE RATIO BETWEEN THE VELOCITY OF DRIVER AND FOLLOWER D1 = diameter of the driver, d2 = diameter of the follower N1= speed of the driver in rpm,n2 = speed of the follower in rpm Length of the belt es over the driver in one minute = ¶ d1.N1 Length of the belt es over the follower in one minute = ¶ d2.N2 Length of the belt in the driver is equal to the length of the follower in one minute revolution ¶ d1.N1 = ¶ d2.N2 Velocity ratio N2/N1 = d1/d2 When the thickness of the belt is considered then velocity ratio N2/N1 = d1+t/d2+t

VELOCITY RATIO OF COMPOUND DRIVE Power is to be transmitted from one shaft to another through number of pulley. Pulley 1 driving the pulley 2,and the pulley 2 and 3 are keyed in same shaft, therefore pulley 1 drives the pulley 3 which in turn the pulley 4 Velocity ratio of pulley 1 & 2 N2/N1 = D1/D2 Velocity ration of pulley 3 & 4 N4/N3 = D3/D4 N2/N1 * N4/N3 = d1/d2*d3/d4 ( N2 = N3 ) N4/N1 = d1*d3/d2*d4 Speed of the last follower = Product of the diameter of the driver Speed of the first driver Product of the diameter of the follower

SLIP OF THE BELT FRICTIONAL GRIP BETWEEN BELT AND PULLEY SOME TIMES BECOME INSUFFICIENT IT CAUSES THE FORWARD MOTION OF THE DRIVER WITHOUT CARRYING THE BELT ,IT MAY ALSO CAUSE THE FORWARD MOTION OF THE BELT WITHOUT CARRYING THE FOLLOWER PULLEY WITH IT. THIS IS CALLED SLIP OF THE BELT AND EXPRESSED IN %

S1% = Slip between the driver and the belt S2% = Slip between the belt and the follower Velocity of the belt ing over the driver per second V = ¶ d1.N1 ¶ d1.N1 * s1 i 60 60 100 = ¶ d1.N1 1 – s1 60 100 Velocity of the belt ing over the follower ¶ d2.N2 = v –v * s2/100 60 = v ( 1- s2/100) ii Substituting ii in i we get ¶ d2.N2/60 = ¶ d1.N1/60(1-s1/100) ( 1- s2/100 )

¶ d2.N2/60 = ¶ d1.N1/60(1-s2/100s1/100+s1*s2/100*100) N2/N1 = d1/d2 ( 1- s2/100 –s1/100) N2/N1=d1/d2 (1- s1+s2 ) 100 N2/N1 = d1/d2 ( 1- s/100) where s=s1+s2 ( total % of slip ) If thickness is considered N2/N1 = d1+t/d2+t ( 1- s/100)

CREEP OF THE BELT BELT ES FROM SLACK SIDE TO TIGHT SIDE THE BELT EXTEND AND CONTRACTS AGAIN WHEN BELT ES FROM TIGHT SIDE TO SLACK SIDE. DUE TO THESE CHANGES THERE IS A RELATIVE MOTIONBETWEEN BELT AND PULLEY SURFACE. THIS RELATIVE MOTION IS TERMED AS CREEP CREEP EFFECT IS TO REDUCE THE SPEED OF FOLLOWER. N2/N1 = d1/d2 * E+ σ2 E+ σ1

POWER TRANSMITTED BY THE BELT It has been already discussed that driver pulley pulls the belt from one side to the other side. Tension on the tight side is greater than the tension on the slack side. Let T1,T2 = Tension in the tight and slack side respectively in Newton's R1 and r2 = Radius of the driver and the follower V = velocity of the belt in m/s Effective turning force at the circumference of the follower is the difference in the tensions ( T1-T2) Work done per second = ( T1-T2)*v N-m/s

INITIAL TENSION OF THE PULLEY IN ORDER TO MOVE THE BELT CONTINUOUSLY OVER THE PULLEY THE END OF THE BELT ARE ED TOGETHER. IN ORDER TO INCREASE THE GRIP THE BELT IS TIGHTENED UP AT THIS STAGE THE PULLEY ARE STATIONARY AND THE BELT IS SUBJECTED TO SOME TENSION CALLED INITIAL TENSION. Let T0 = intial tension in the belt T1 = Tension in the tight side T2 = Tension in the slack side

α = Co efficient of increase of the belt length per unit force A little consideration will show that the increase of tension in the tight side = ( T1 – T0 ) Length of the belt on the tight side = α ( T1 – T0 ) Decrease of tension in the slack side = ( T0 – T2 ) Decrease in the length of the belt on the slack side = α ( T0 – T2 ) Assuming that length of the belt remains constant when both in rest and in motion, therefore length of the belt in tight side is equal to the length of the belt in the slack side α ( T1 – T0 ) = α ( T0 – T2 ) T0 = T1+T2 2

V BELT DRIVE 1. 2. 3. 4. 5.

6. 7. 8. 9.

It is used when amount of power to be transmitted between two pulley is very near to each other. It is made up of fabric and cords moulded in rubber covered with fabric and rubber. The belts are made up of trapezoidal shape. The included angle of the v – belt is usually 30° - 40°s In case of flat belt the belt runs over the pulley but in the case of the V- belt the rim of the pulley is grooved in which the belts run over. The effect of the groove is to increase the frictional grip of the v-belt and to reduce the tendency of the slipping. Clearance is provided at the bottom of the groove to prevent the touching to the bottom as it becomes from wear. V-belt may be inclined at any angle which may be tight at the top or bottom In order to increase the power output several v-belt may be operated side by side .

10.In multiple v – belt drive all the belt should stretch at the same rate so that the load is equally divided between them. 11.When one set of the belt breaks the entire set should be changed. 12.If only one belt is replaced the new unworn and unstressed belt will be more tightly stretched and move with different velocity.

ADVANTAGE AND DISADVANTAGE OF V-BELT DRIVE OVER FLAT DRIVE  ADVANTAGES  Drive is positive,

   

because the slip between belt and groove is neglible. Longer life 3 to 5 years Can be easily installed and removed More power is transmitted in v – belt May be operated in either direction tight side at the top or bottom

 DISADVANTAGES  Cannot be used with

large centre distance.  Construction for the vbelt pulley is more complicated than the flat belt.  Belt life is greatly influenced with the temperature change,improper belt tension and mismatching of belt lengths  Prevents use of v-belt below speed of 5 m/s and above 50 m/s

ROPE DRIVE  ROPE DRIVE IS USED WHEN LARGE AMOUNT

OF POWER IS TO BE TRANSMITTED.  FRICTIONAL GRIP IN THE ROPE DRIVE IS MORE THAN THAT IN THE V – DRIVE  NUMBER OF SEPARATE DRIVE IS TAKEN FROM THE ONE DRIVING PULLEY  IT USES FOLLOWING TWO TYPES OF ROPE Wire rope = When pulleys are about 60 mts apart. Fibre rope = when pulleys are about 150 mts apart.

FIBRE ROPE AND THE WIRE ROPE  FIBRE ROPE  MADE UP OF

HEMP,MANILA AND COTTON.  SINCE HEMP,AND MANILA ARE ROUGH THE ROPE MADE UPOF THIS IS NOT FLEXIBLE AND POOR MECHANICAL PROPERTIES  HEMP AND MANILA ROPES ARE BENT OVER THE PULLEY ,CAUSING THE ROPE TO WEAR.

 WIRE ROPE  THESE ROPE ARE



  

USED IN ELEVATOR,CRANES,C ONVE YOR. IT RUNS OVER THE GROOVED PULLEY BUT REST ON THE BOTTOM OF THE GOOVES. LIGHTER IN WEIGHT OFFER SILENT OPERATION WITHSTAND SHOCK LOADS

 IN ORDER TO

 DO NOT FAIL

MINIMIZE THIS DEFECT IT IS LUBRICATED WITH TAR,TALLOW OR GRAPHITE  THE LUBRICANT ALSO MAKE ROPE MOISTURE PROOF  SUITABLE ONLY FOR HAND OPERATED HOISTING MACHINERY.  COTTON ROPES ARE SMOOTH AND SOFT

SUDDENLY  THE EFFICIENCY IS HIGH  COST IS LOW

CHAIN DRIVE  IN ORDER TO AVOID THE SLIPPING DURING THE 









TRANSMISSION THE STEEL CHAINS ARE USED. MADE UP OF RIGID LINKS WHICH ARE HINGED TOGETHER IN ORDER TO PROVIDE NECESSARY FLEXIBILITY FOR MOVING ROUND THE DRIVING AND DRIVEN PULLEY WHEELS HAVING THE PROJECTING TEETH AND THE CHAINS ARE FIXED INTO THE CORRESPONDENCE TEETH . THE WHEELS AND THE CHAIN ARE CONSTRAINED TO MOVE TOGETHER WITHOUT SLIPPING. THE TOOTHED WHEEL ARE KNOWN AS SPROCKET WHEEL WHICH RESEMBLE TO SPUR GEAR. TRANSMIT MOTION WHEN DISTANCE BETWEEN

ADVANTAGE AND DISADVANTAGE OF CHAIN DRIVE ADVANTAGE  NO SLIP IS TAKING  

 

PLACE MADE UP OF METAL OCCUPY LESS SPACE USED WHEN DISTANCE BETWEEN SHAFT IS LESS HIGH TRANSMISSION EFFICIENCY GIVES LESS LOAD ON

DISADVANTAGE  PRODUCTION COST

OF CHAIN IS HIGH  NEED ACCURATE MOUNTING AND MAINTENANCE  HAS VELOCITY FLUCTUATIONS.

USED IN PITCH CHAIN DRIVE CIRCLE PITCH OF THE CHAIN

DIAMETER OF THE SPROCKET

 IT IS THE DISTANCE

 IT IS THE DIAMETER

BETWEEN THE HINGE CENTRE OF A LINK AND THE CORRESPONDING CENTRE OF THE ADJACENT LINK.

OF THE CIRCLE ON WHICH THE HINGE CENTRE OF THE CHAIN LIE WHEN CHAIN IS WRAPPED ROUND THE SPROCKET