TODAY’S TOPIC Chain Drivers GROUP#1 08-EP-53 M OSAMA AZAM 08-ME-55 UMER AKRAM 08-EP-54 M SHAHBAZ SAEED 08-EP-33 M UMER FAROOQ

TODAY’S TOPICTODAY’S TOPIC

Chain DriversChain Drivers

GROUP#1GROUP#1

08-EP-53 M OSAMA AZAM08-EP-53 M OSAMA AZAM08-ME-55 UMER AKRAM08-ME-55 UMER AKRAM08-EP-54 M SHAHBAZ SAEED08-EP-54 M SHAHBAZ SAEED08-EP-33 M UMER FAROOQ08-EP-33 M UMER FAROOQ

Why we need chain Why we need chain drivers?drivers?

On belt and rope drives that slipping On belt and rope drives that slipping may occur. In order to avoid slipping, may occur. In order to avoid slipping, steel chains are used. steel chains are used.

INTRODUCTIONINTRODUCTION DEFINITIONDEFINITION

The chains are made up of number of rigid links which are hinged together by pin joints in order to provide the necessary flexibility for wrapping round the driving and driven wheels. These wheels have projecting teeth of special profile and fit into the corresponding recesses in the links of the chain as shown in Fig. The toothed wheels are known as *sprocket

wheels or simply sprockets.

Explanation through diagramExplanation through diagram

Practical applications of Practical applications of chain drives chain drives

The chains are mostly used to transmit The chains are mostly used to transmit motion and power from one shaft to motion and power from one shaft to another, when the centre distance between another, when the centre distance between their shafts is short such as in their shafts is short such as in bicyclesbicycles, , motor cyclesmotor cycles, , agricultural agricultural machinery, machinery, conveyors, rolling mills, road rollers etc. conveyors, rolling mills, road rollers etc.

The chains may also be used for long centre The chains may also be used for long centre distance of upto 8 metres. distance of upto 8 metres.

The chains are used for velocities up to 25 The chains are used for velocities up to 25 m / s and for power upto 110 kW. In some m / s and for power upto 110 kW. In some cases, higher power transmission is also cases, higher power transmission is also possible.possible.

Advantages and Disadvantages of Advantages and Disadvantages of Chain Drive over Belt or Rope Chain Drive over Belt or Rope

DriveDrive

AdvantagesAdvantages

As no slip takes place during chain drive, hence perfect velocity ratio is obtained.

Since the chains are made of metal, therefore they occupy less space in width than a belt or rope drive

It may be used for both long as well as short distances.

It gives a high transmission efficiency (upto 98 It gives a high transmission efficiency (upto 98 percent).percent).

It gives less load on the shafts.It gives less load on the shafts.

It has the ability to transmit motion to several shafts It has the ability to transmit motion to several shafts by one chain only.by one chain only.

It transmits more power than belts.It transmits more power than belts.

It permits high speed ratio of 8 to 10 in one step.It permits high speed ratio of 8 to 10 in one step.

It can be operated under adverse temperature and It can be operated under adverse temperature and atmospheric conditions.atmospheric conditions.

DisadvantagesDisadvantages

The production cost of chains is relatively The production cost of chains is relatively high.high.

The chain drive needs accurate mounting The chain drive needs accurate mounting and careful maintenance, particularly and careful maintenance, particularly lubrication and slack adjustment.lubrication and slack adjustment.

The chain drive has velocity fluctuations The chain drive has velocity fluctuations especially when unduly stretchedespecially when unduly stretched..

Terms Used in Chain DriveTerms Used in Chain Drive

Pitch of chainPitch of chain

It is the distance between the hinge centre of a link and the corresponding hinge centre

of the adjacent link, as shown in Fig. It is usually denoted by p.

Pitch circle diameter of chain Pitch circle diameter of chain

sprocket.sprocket. It is the diameter of the circle on which the hinge It is the diameter of the circle on which the hinge centres of the chain lie, when the chain is centres of the chain lie, when the chain is wrapped round a sprocket as shown in above wrapped round a sprocket as shown in above Fig. The points Fig. The points A, B, C, A, B, C, and and D D are the hinge are the hinge centres of the chain and the circle drawn through centres of the chain and the circle drawn through these centres is called pitch circle and its these centres is called pitch circle and its diameter diameter (D) (D) is known as pitch circle diameter.is known as pitch circle diameter.

Relation Between “Pitch” and Relation Between “Pitch” and “Pitch Circle Diameter (“Pitch Circle Diameter (pp and and

d)d)

Relation Between “Pitch” and Relation Between “Pitch” and “Pitch Circle Diameter (“Pitch Circle Diameter (pp and and

d)d) A chain wrapped round A chain wrapped round

the sprocket is shown the sprocket is shown in Fig.. Since the links in Fig.. Since the links of the chain are rigid, of the chain are rigid, therefore pitch of the therefore pitch of the chain does not lie on chain does not lie on the arc of the pitch the arc of the pitch circle. circle.

The pitch length The pitch length becomes a chord. becomes a chord.

Consider one pitch Consider one pitch length AB of the chain length AB of the chain subtending an angle subtending an angle ӨӨ at the centre of at the centre of sprocket (or pitch sprocket (or pitch circle),circle),

LetLet

D D = Diameter of the pitch circle, and= Diameter of the pitch circle, and

T T = Number of teeth on the sprocket. = Number of teeth on the sprocket. From Fig. we find that pitch of the chain

We can observe that:We can observe that: AC = OA sinAC = OA sinθθ = OA sin(180/ = OA sin(180/T T ).). As AC = As AC = pp/2 and OA = /2 and OA = dd/2,/2, Therefore,Therefore, pp/2 = (/2 = (dd/2)sin(180//2)sin(180/T T ))

p p = = dd sin (180/ sin (180/T T )) Or Or dd = = pp cosec (180/ cosec (180/T T ))

Kinematics of Chain DriveKinematics of Chain Drive

Let us consider two sprockets, in which driven Let us consider two sprockets, in which driven sprocket is larger than the driver sprocket. AC is sprocket is larger than the driver sprocket. AC is the pitch of driving sprocket, and BBthe pitch of driving sprocket, and BB22 is the pitch is the pitch of driven sprocket.of driven sprocket. We want to compare the We want to compare the angular velocities of two sprockets.angular velocities of two sprockets.


Initially when the driving sprocket was at A, the Initially when the driving sprocket was at A, the driven was at B, with the centers Odriven was at B, with the centers O11 and O and O22 respectively. To find the instantaneous centre, we respectively. To find the instantaneous centre, we produce Oproduce O11OO2 2 and AB to meet an pointand AB to meet an point I I..


If If ωω11 and and ωω22 are the angular velocities of are the angular velocities of driver and driven sprockets respectively, driver and driven sprockets respectively, then,then,

ωω1 1 * * OO11I = I = ωω2 2 * * OO22II

ωω11/ / ωω2 2 = = OO22I/ OI/ O11II

= (O= (O22OO11+ O+ O11I)/ OI)/ O11II

ωω11/ / ωω22 = 1+(O = 1+(O22OO11/ O/ O11I).I).

So, So, ωω11/ / ωω22 is inversely proportional to “O is inversely proportional to “O11I”.I”.


The instantaneous centre of rotation changes The instantaneous centre of rotation changes along with the rotation.along with the rotation.

The relation The relation ωω11/ / ωω22 = 1+(O = 1+(O22OO11/ O/ O11I) represents I) represents the minimum velocity ratio, as B is the lowest the minimum velocity ratio, as B is the lowest point of pitch and I is at the greatest distance point of pitch and I is at the greatest distance from the driving sprocket.from the driving sprocket.


When A moves to AWhen A moves to A11, B moves to , B moves to point Bpoint B11. So the instantaneous centre . So the instantaneous centre of rotation will be Iof rotation will be I11.which as .which as compared to I, is nearer from the compared to I, is nearer from the driven sprocket. So velocity ratio will driven sprocket. So velocity ratio will be maximum. be maximum.


In actual practice, the smaller In actual practice, the smaller sprocket must have a minimum of 18 sprocket must have a minimum of 18 teeth and hence the variation of teeth and hence the variation of velocity ratio from the mean value is velocity ratio from the mean value is very small.very small.

Classification of ChainsClassification of Chains

The Chains, on the The Chains, on the basis of their use, are basis of their use, are classified into the classified into the following three following three groups:groups:

1.1. Hoisting or hauling (or Hoisting or hauling (or crane) chains.crane) chains.

2.2. Conveyer (or tractive) Conveyer (or tractive) chains.chains.

3.3. Power transmitting (or Power transmitting (or driving) chains.driving) chains.

Hoisting or hauling (or crane) Hoisting or hauling (or crane) chainschains

These chains are used for hoisting These chains are used for hoisting and hauling purposes. These are of and hauling purposes. These are of two types:two types:

1.1. Chains with oval links.Chains with oval links.

2.2. Chains with square links.Chains with square links.


1.1. Chains with oval Chains with oval links:links:

The links are The links are of oval shape. The of oval shape. The joint of each link is joint of each link is welded. Such type welded. Such type of chains are used of chains are used only at low speeds only at low speeds such as chain hoists such as chain hoists and in anchors of and in anchors of marine work.marine work.


Chains with square links:Chains with square links:

The links are of square The links are of square shape. Such type of chains are used shape. Such type of chains are used in hoists, cranes, dredges. These in hoists, cranes, dredges. These are cheaper than oval link chains, are cheaper than oval link chains, but the kinking occurs easily on but the kinking occurs easily on overloading.overloading.

Conveyer ChainsConveyer Chains

These chains are These chains are used for elevating used for elevating and conveying the and conveying the material material continuously. These continuously. These are of two types:are of two types:

1.1. Detachable or hook Detachable or hook joint type chain.joint type chain.

2.2. Closed joint type Closed joint type chain.chain.

Conveyer ChainsConveyer Chains

Properties:Properties:

1.1. Usually manufactured by cast iron.Usually manufactured by cast iron.

2.2. Do not have smooth running Do not have smooth running qualities.qualities.

3.3. Run at low speeds of about 3 to 12 Run at low speeds of about 3 to 12 Km/h.Km/h.

Power transmittin chainsPower transmittin chains

•Transmission of power when the distance between the shafts is shortTransmission of power when the distance between the shafts is short•Have provision for efficient lubricationHave provision for efficient lubricationThree typesThree types1.1.Block chainBlock chain2.2.Bush roller chainBush roller chain3.3.Inverted tooth or silent chainInverted tooth or silent chain


1.1. Block chainBlock chain it is also known as bush chainit is also known as bush chain Produce noise because of rubbing between teeth and linksProduce noise because of rubbing between teeth and links


Bush Roller chainBush Roller chain

it consist of it consist of

1.1. Outer plate or pin link plateOuter plate or pin link plate

2.2. Inner plate or roller link plateInner plate or roller link plate

3.3. Pins Pins

4.4. BushesBushes

5.5. Rollers Rollers

Advantages of bush chainAdvantages of bush chain•Extremely strongExtremely strong•Simple in constructionSimple in construction•It gives good service under sever It gives good service under sever conditioncondition•Can be used with little lubricationCan be used with little lubrication•Produce little noiseProduce little noise•Rollers resist wearRollers resist wear

inverted tooth or silent chaininverted tooth or silent chain

PurposePurpose•Noiseless runningNoiseless running•Eliminates the effects on Eliminates the effects on chain and sprocket caused by chain and sprocket caused by stretchingstretching

Length of chainLength of chain

L=L=∏∏(r(r11 + r + r22)+2x+ (r)+2x+ (r11 - r - r22))22 /x /x

Numerical ExamplesNumerical Examples

EXAMPLE #1:EXAMPLE #1:

A chain drive is used for reduction A chain drive is used for reduction of speed from 320rpm to 128rpm. The of speed from 320rpm to 128rpm. The number of teeth on driven sprocket is 50, number of teeth on driven sprocket is 50,

(a)Find the number of teeth on driving (a)Find the number of teeth on driving sprocket.sprocket.

(b)If the pitch circle diameter of driving (b)If the pitch circle diameter of driving sprocket is 300mm, find out the pitch of sprocket is 300mm, find out the pitch of chain drive.chain drive.


A chain drive having a speed of driving A chain drive having a speed of driving sprocket 220rpm, and the number of sprocket 220rpm, and the number of teeth on the driving and driven sprocket teeth on the driving and driven sprocket are 24 and 48 respectively.are 24 and 48 respectively.

(a) Find out the driven speed of sprocket.(a) Find out the driven speed of sprocket.

(b) If p=25mm, find out the circle (b) If p=25mm, find out the circle diameter of driven sprocket.diameter of driven sprocket.

(c) If k=33, find out the length of chain.(c) If k=33, find out the length of chain.


A chain drive is used for reduction of A chain drive is used for reduction of speed from 240rpm to 120 rpm. The speed from 240rpm to 120 rpm. The number of teeth on the driving number of teeth on the driving sprocket is 20. Find the number of sprocket is 20. Find the number of teeth on the driven sprocket. If the teeth on the driven sprocket. If the pitch circle diameter of the driven pitch circle diameter of the driven sprocket is 800mm, determine the sprocket is 800mm, determine the pitch and length of chain.pitch and length of chain.

Numerical ProblemNumerical Problem

A chain drive is used for increase in A chain drive is used for increase in speed from 180rpm to 360rpm. The speed from 180rpm to 360rpm. The number of teeth on the driven sprocket is number of teeth on the driven sprocket is 30. If the pitch circle diameter of the 30. If the pitch circle diameter of the driving sprocket is 900 mm and center to driving sprocket is 900 mm and center to center distance between two sprockets is center distance between two sprockets is 1200mm. 1200mm.

Determine the length and the pitch of the Determine the length and the pitch of the chain.chain.

Documents

TODAY’S TOPIC Chain Drivers GROUP#1 08-EP-53 M OSAMA AZAM 08-ME-55 UMER AKRAM 08-EP-54 M SHAHBAZ SAEED 08-EP-33 M UMER FAROOQ