Belt, Rope and Chain Drive

8/9/2019 Belt, Rope and Chain Drive

1/26

Belt Rope andChain Drives


2/26

Introduction:

The belts or ropes are used to transmit power from one shaft to another by means of

pulleys which rotate at the same speed or at different speeds. The amount of powertransmitted depends upon the following factors:

The velocity of the belt. 1

The tension under which the belt is placed

on the pulleys. 2

3The arc of contact between the belt and the

smaller pulley.


3/26

Types of Belts:

1. Flat belt : The flat belt is mostly used in the factories and workshops, where amoderate amount of power is to be transmitted, from one pulley to another when the

two pulleys are not more than 8 meters apart.

2. V-belt : The Vbelt is mostly used in the factories and workshops, where amoderate amount of power is to be transmitted, from one pulley to another, when the

two pulleys are very near to each other.

!. Circular belt or rope : The circular belt or rope is mostly used in the factories andworkshops, where a "reat amount of power is to be transmitted, from one pulley to

another, when the two pulleys are more than 8 meters apart.


4/26

Types of Flat Belt Drives:

Crossed ortwist belt

drive

Compound

belt drive

Quarter turn belt

drive

Open

belt

drive

Belt drive with

idler pulleys

Stepped or

cone pulley

drive

Belt

Drives

Fast and

loose pulleydrive

Fast and

loose pulleydrive


5/26

Velocity Ratio of Belt Drive:

It is the ratio between the velocities of the driver and the follower or

driven.

It may be expressed, mathematically, as discussed below:

Let d 1 = Diameter of the drier,

d ! = Diameter of the follower,

N 1= "peed of the drier in r.p.m., and N ! = "peed of the follower in r.p.m.

Length of the belt that passes oer the drier, in one minute= π d 1. N 1

"imilarly, length of the belt that passes oer the follower,

in one minute = π d ! . N !

"ince the length of belt that passes oer the drier in one minute is e#ual to the

length of belt that passes oer the follower in one minute,

therefore π d 1 . N 1 = π d ! . N !

∴ $elocity ratio,


6/26

Velocity Ratio of a Compound Belt Drive:

"ometimes the power is transmitted from one shaft to another, through a

number of pulleys.

Let d 1 = Diameter of the pulley 1,

N 1 = "peed of the pulley 1 in r.p.m.,

d !, d %, d &, and N !, N %, N &= 'orresponding alues for pulleys !, % and &. (e

)now that elocity ratio of pulleys 1 and !,

"imilarly, elocity ratio of pulleys % and &,

*ultiplying the aboe e#uations

"ince +!=+%, therefore


7/26

Slip of Belt:

Let s1 - = "lip between the drier and the belt, and

s! - = "lip between the belt and the follower.

∴ $elocity of the belt passing oer the drier per second

……………..(i)

and elocity of the belt passing oer the follower per second,

"ubstituting the alue of from e#uation (i),


8/26

+umerical 1: An enine! runnin at "#$ r.p.m.! drives a line s%aft &y means of a &elt. '%eenine pulley is #$ mm diameter and t%e pulley on t%e line s%aft &ein #$ mm. A *$$ mm

diameter pulley on t%e line s%aft drives a "#$ mm diameter pulley +eyed to a dynamo s%aft. ,ind

t%e speed of t%e dynamo s%aft! -%en:

". '%ere is no slip! and

. '%ere is a slip of / at eac% drive.

#olution:ien: N 1 = 1/0 r.p.m. d 1 = /0

mm d ! = &/0 mm d % = 200 mm d &

= 1/0 mm

Let N &

= "peed of the dynamo

shaft.


9/26

Creep of Belt:

(here:

31 and 3 ! = "tress in the belt on the tight and slac) side

respectiely, and 4 = 5oung6s modulus for the material of the belt.


10/26

Numerical 2: The power is transmitted from a pulley 1 mdiameter running at 200 r.p.m. to a pulley 2.25 m diameter by

means of a belt. Find the speed lost by the driven pulley as aresult of creep if the stress on the tight and slac! side of the beltis 1." #$a and 0.5 #$a respectively. The %oung&s modulus for thematerial of the belt is 100 #$a.

Solution


11/26

Power Transmitted by a Belt

T 1 and T 2 = Tensions in the tight and slack side of the beltrespectively innewtonsr 1 and r 2 = Radii of the driver and follower respectively and

v = !elocity of the belt in "#s$ The e%ective t&rning 'driving( force at the circ&"ference of thefollower is the di%erence between the two tensions 'i.e$ T 1 )T 2($* +ork done per second = 'T 1 ) T 2( v ,-"#sand power trans"itted $ = 'T 1 ) T 2( v +


12/26

Rope Drive

The rope drives are widely &sed where a large a"o&nt of poweris to be trans"itted fro" one p&lley to another over aconsiderable distance$

.t "ay be noted that the &se of /at belts is li"ited for thetrans"ission of "oderate power fro" one p&lley to anotherwhen the two p&lleys are not "orethan 0 "etres apart$

The rope drives &se the following two types of ropes :1. Fibre ropes and 2. +ire ropes$

The bre ropes operate s&ccessf&lly when the p&lleys are abo&t3 "etres apart while the wire ropes are &sed when the p&lleysare &pto 143 "etres apart$


13/26

Fiber Ropes

The ropes for trans"itting power are &s&ally "ade fro" bro&s"aterials s&ch as he"p "anila and cotton$

5ince the he"p and "anila bers are ro&gh therefore the

ropes "ade fro" these bers are not very /e6ible andpossesses poor "echanical properties$

The he"p ropes have less strength as co"pared to "anilaropes$

.n order to "ini"i7e this wear the rope bers are l&bricatedwith a tar tallow or graphite$ The l&brication also "akes therope "oist&re proof$

The he"p ropes are s&itable only for hand operated hoisting"achinery

and as tie ropes for lifting tackle hooks etc$


14/26

Advantages of Fiber Rope Drives

The ber rope drives have the following advantages :1. They give s"ooth steady and 8&iet service$2. They are little a%ected by o&t door conditions$3. The shafts "ay be o&t of strict align"ent$4. The power "ay be taken o% in any direction and in fractional

parts of the whole a"o&nt$. They give high "echanical e9ciency$


15/26

!"eave for Fiber Ropes

The ber ropes are &s&ally circ&lar in cross-section as shown inFig$ 11$22 'a($ The sheave for the ber ropes is shown in Fig$11$22 'b($ The groove angle of the p&lley for rope drives is&s&ally 4;$


16/26

#ire Ropes

+hen a large a"o&nt of power is to be trans"itted over longdistances fro" one p&lley to another 'i.e$ when the p&lleys are &pto143 "etres apart( then wire ropes are &sed$+idely &sed in elevators "ine hoists cranes conveyors ha&lingdevices and s&spension bridges$


17/26

Ratio of Driving Tensions forRope Drive

Numerical ': ( rope drive transmits )00 !* from a pulley ofe+ective diameter " m which runs at a speed of ,0 r.p.m. Theangle of lap is 1)0- the angle of groove "5- the coe/cient offriction 0.2 the mass of rope 1.5 !g m and the allowable tensionin each rope 2"00 N. Find the number of ropes reuired.

Solution


18/26

Chain Drives

The chains are "ade &p of rigid links which are hinged together inorder toprovide the necessary /e6ibility for warping aro&nd the driving anddrivenwheels$ The wheels and the chain are th&s constrained to "ove together

witho&tslipping and ens&res perfect velocity ratio$

The toothed wheels are known as sprocket wheels or si"plysprockets.

These wheels rese"ble to sp&r gears$ The chains are "ostly &sed totrans"it "otionand power fro" one shaft to another when the distance between thecentres of the shafts is short s&ch as in bicycles "otor cyclesagric&lt&ral "achinery road rollers etc$


19/26

Advantages1.


20/26


21/26

%lassi&'ation of %"ains

The chains on the basis of their &se are classied into thefollowing three gro&ps :1. >oisting and ha&ling 'or crane( chains2. Conveyor 'or tractive( chains and

3. ?ower trans"itting 'or driving( chains$


22/26

(oisting and (a)ling%"ains


23/26

%onveyor %"ains

These chains are &sed for elevating and conveying the "aterialscontin&o&sly$ The conveyor chains are of the following two types:1. Detachable or hook @oint type chain as shown in Fig$ 11$A3'a( and

2. Closed @oint type chain as shown in Fig$ 11$A3 'b($ The conveyor chains are &s&ally "ade of "alleable cast iron$ These chains do not have s"ooth r&nning 8&alities$ Theconveyor chains r&n at slow speeds of abo&t A to 12 k"$p$h$


24/26

Power Transmitting%"ains


25/26

Bush roller chain. < b&sh roller chain as shown in Fig$ 11$A2consists of o&ter plates or pin link plates inner plates or roller linkplates pins b&shes and rollers$ < pin passes thro&gh the b&shwhich is sec&red in the holes of the roller between the two sides of

the chain$ The rollers are free to rotate on the b&sh which protectthe sprocket wheel teeth against wear$


26/26

Belt, Rope and Chain Drive

Documents

Transcript of Belt, Rope and Chain Drive