07-05-2014, 12:12 PM
Chain Drivers
Chain Drivers.ppt (Size: 964 KB / Downloads: 260)
INTRODUCTION
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.
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.
Advantages
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
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.
Numerical Examples
A chain drive is used for reduction of speed from 240rpm to 120 rpm. The number of teeth on the driving sprocket is 20. Find the number of teeth on the driven sprocket. If the pitch circle diameter of the driven sprocket is 800mm, determine the pitch and length of chain.
[b]Numerical Problem[/b]
A chain drive is used for increase in speed from 180rpm to 360rpm. The number of teeth on the driven sprocket is 30. If the pitch circle diameter of the driving sprocket is 900 mm and center to center distance between two sprockets is 1200mm.
Determine the length and the pitch of the chain.