GOVERNMENT ENGINEERING COLLEGE,DAHOD MECHANICAL DEPARTMENT TOPIC : CHAIN DRIVE 110180119111 DANGI SANDIP B. 130180119110 THAKOR VISHNUJI F. 120180119001 PATEL CHINAL 110180119095 SOLANKI MAYANK

CHAIN DRIVE DEFINITION 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 diagram

Practical applications of chain drives The chains are mostly used to transmit motion and power from one shaft to another, when the centre distance between their shafts is short such as in bicycles, motor cycles, agricultural machinery, conveyors, rolling mills, road rollers etc. The chains may also be used for long centre distance of upto 8 metres. The chains are used for velocities up to 25 m / s and for power upto 110 kW. In some cases, higher power transmission is also possible.

Pitch 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.

Kinematics of Chain Drive Let us consider two sprockets, in which driven sprocket is larger than the driver sprocket. AC is the pitch of driving sprocket, and BB2 is the pitch of driven sprocket. We want to compare the angular velocities of two sprockets.

Kinematics of Chain Drive Initially when the driving sprocket was at A, the driven was at B, with the centers O1 and O2 respectively. To find the instantaneous centre, we produce O1O2 and AB to meet an point I.

Kinematics of Chain Drive If ω1 and ω2 are the angular velocities of driver and driven sprockets respectively, then, ω1 * O1I = ω2 * O2I ω1/ ω2 = O2I/ O1I = (O2O1+ O1I)/ O1I ω1/ ω2 = 1+(O2O1/ O1I). So, ω1/ ω2 is inversely proportional to “O1I”.

Kinematics of Chain Drive The instantaneous centre of rotation changes along with the rotation. The relation ω1/ ω2 = 1+(O2O1/ O1I) represents the minimum velocity ratio, as B is the lowest point of pitch and I is at the greatest distance from the driving sprocket.

Kinematics of Chain Drive When A moves to A1, B moves to point B1. So the instantaneous centre of rotation will be I1.which as compared to I, is nearer from the driven sprocket. So velocity ratio will be maximum.

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

Classification of Chains The Chains, on the basis of their use, are classified into the following three groups: Hoisting or hauling (or crane) chains. Conveyer (or tractive) chains. Power transmitting (or driving) chains.

Hoisting or hauling chains These chains are used for hoisting and hauling purposes. These are of two types: Chains with oval links. Chains with square links.

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

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

Advantages Since the chains are made of metal, therefore they occupy less space in width than a belt or rope drive As no slip takes place during chain drive, hence perfect velocity ratio is obtained. It may be used for both long as well as short distances .

It gives a high transmission efficiency (upto 98 percent). It gives less load on the shafts. It has the ability to transmit motion to several shafts by one chain only. It transmits more power than belts. It permits high speed ratio of 8 to 10 in one step. It can be operated under adverse temperature and atmospheric conditions.

Disadvantages The production cost of chains is relatively high. The chain drive needs accurate mounting and careful maintenance, particularly lubrication and slack adjustment. The chain drive has velocity fluctuations especially when unduly stretched.