 సిలాయిను రిమ్వాస్క్గంస్ ఆరౕావాస్ర నార్లుడిల్చివిరందర్. అచ్ంపు�演講 కారిరోను మెరోన్స్స్ండంస్స్. The learning outcome of the session is expected to have at the end the students will be able to design the flat belt drive for given application using manufacturer's data. The belt drive consists of pulleys mounted on driver and driven shafts and a continuous belt is passed on the pulleys which transmits the power. The belt drives are extensively used in many industrial applications like conveyors, machine tools, compressors, blowers, etc. The belts and pulleys being standard mechanical elements are required to be selected from manufacturer's data for all practical applications. The belt drive consists of a continuous belt which is passed over the driving pulleys and driven pulleys and the power is transmitted by this belt by means of friction between a pulleys and a belt. So pause this video for a while and think on identifying the design parameters. For the design of the belt drive, the input data which is required is power to be transmitted, input speed, output speed, the center distance, belt velocity, belt system which may be open or crossed, the various service conditions and the manufacturer's data. The design procedure involves the following steps. First we have to calculate the diameter of a smaller pulleys D1 by making use of the velocity of the belt. This velocity of the belt is a pitch line velocity or a linear velocity considered in design. The optimum value of this velocity is assumed for many of the applications between 18 to 20 meters per second because of overall economy of the drive. So once we decide upon this velocity we can calculate the diameter D1 by making use of this equation. The D1 value once it is found out one has to select the standard pitch diameter from manufacturer's data because this is available as a standard mechanical element. For the reference here I have shown the preferred diameters of the pulleys which is extensive table here I have made it available some values. So for example if I get the value around 150 mm or 155 mm my job is just to select the standard value as 160 mm or 140 mm, nearest to that one. So this is the way we have to fix the diameter D1 of a smaller pulleys. Then we can calculate the diameter D2 by considering the speed ratio as equation N1 by N2 is equal to D2 by D1 in which the slip is not considered. However in some of the applications the slip at both the pulleys between the belt and drive pulleys is considered and this equation can be made use of. So here we can find out D2 and once again the same thing we have to select the standard diameter from a table. So this is the way we can decide upon the diameter D1 and D2 as a first step of design. Once we get the selected diameter from standard then the velocity what we started with is going to change and that is why we corrected has to be calculated once again by making use of selected diameter D1 by this equation pi D1 N1 by 60. The another step is to correct use of load correction factor by referring manufacturers data. Because while supplying the standard belt the manufacturer uses some type of load and whereas in practical applications the type of load may change according to the application. So that must be accounted by a factor called as load correction factor. So this is the table for the reference for you just if I select certain application like centrifugal pump I have to select this load correction factor as 1.2. The angle of contact between the smaller pulleys and the belt has got a prime importance in power transmission. That is why it has been calculated by considering the geometry as small angle between the belt and the smaller pulleys 180 degrees minus 2 sine inverse of D2 minus D1 upon 2C if the belt is open belt type and if it is a cross belt system it is 180 degrees plus 2 sine inverse of D2 minus D1 upon 2C. So this is the way we can calculate the angle of contact of a smaller pulleys with the belt. Now this has been used to define or to select the standard value of arc of contact factor from manufacturer's data because manufacturer has been supplying the power rating of the belt based upon the angle of contact of 180 degrees. However in practical application this may differ. To account for this difference we have to make use of this angle theta s. So for example if the angle theta is around 140 degree if I calculate my factor becomes 1.19 which is selected from this table. So after getting these two factors F and FT as I said we can calculate the design power of the belt. So design power of the belt is calculated by a required rating power of the belt to be transmitted multiplied by the factors F and FT. Then the manufacturer has provided another data about the belt specification as its power rating in terms of kilowatt per ply per mm width of the belt which has been operated at particular velocity. For example here it is 5.08 m per second. So what does it mean that if I consider a standard belt Dunlop Fort belt then its power rating provided by the manufacturer is 0.0147 kilowatt per ply thickness and per mm width operated at velocity 5.08 m per second. However we are using this belt for our corrected velocity or actual velocity of the belt which may not be 5.08. So I have to multiply this to this and we get a power rating of the belt which we are going to actually use for practical application. A similar is the case for another variety a Dunlop high speed in which the same thing is considered. After knowing the power rating of the belt's PR which we are going to use actually the width of the belt is calculated by considering the equation a design power divided by power rating into number of plies. This understanding means number of plies is construction of the belt. Normally the flat belt is consisting of number of layers cemented together having certain thickness for every layer. Every layer is called the ply. So for example this is the figure I have shown over here in which I have shown the four ply belts. So you can identify ply 1, 2, 3 and 4. So these are the four ply belts similarly practical manufacturing standard belts are available are 3, 4, 5, 6 normally which are used in the industries. And these belts are produced with the standard width of certain 25, 40 shown over here. So my job is just to calculate the width by equation this and then I have to select according to the calculated width the nearest value available in particular ply. For example I can calculate the width of the belt by considering 3 ply I put number of plies as 3 I get certain value of W. Then I check in 3 ply catalog where it will be available in standard width. Similarly the process is continued for all the alternatives and the best alternative is decided as a selection of the belt in terms of the width of the belt. Then we have to calculate the length of the belt. So length of the belt depends upon whether system is open or cross. This is the open belt system I have shown over here for your understanding. The length of the belt consists of the arc length AB, arc BCD, the length D and the length arc AFE. So this is the way we can calculate the length of the belt and corresponding considering the dimensions of the pulleys and angle. We get an equation for length of the belt 2C plus pi by 2 D1 plus D2 plus D2 minus D1 whole square upon 4C. This is a case for open belt system. If the belt is crossed the belt goes cross from this pulleys to this pulleys and it once again comes from this pulleys as a cross over this pulleys. So length is going to be increased for same center distance and that is why this D2 plus D1 square will be in the equation. So that is the only change. Accordingly we get the length of the belt as a requirement of design. So this gives me a solution what the procedure are used for design of the flat belt drive using a manufacturer's data wherever necessary so that all practical applications will met with the solution. In which we got diameter of smaller pulleys D1, diameter of larger pulleys D2, width of the belt W, number of pulleys N and length of the belt. So my references are shown over here. Thank you.