 Hello friends, I am Sanju Vinayak, Assistant Professor in Department of Mechanical Engineering, Walter Institute of Technology, Swalapur. In this video, I am explaining the design procedure of V-Belt drive using manufacturer's data. At the end of this session, students will be able to design the V-Belt drive for given application using manufacturer's data. As you know, 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 industrial applications such as conveyors, machine tools, compressors, etc. Belts and pulleys being standard mechanical elements, they are required to be selected from manufacturer's data for all practical applications. Here we find the belt drive system in which the driving pulleys is a driven pulleys and a continuous belt is passed. In this case, we are talking about the V-Belt. This is the V-Belt having a trapezoidal cross section which has got a frictional principle to transmit the power at the edges. These edges and the groove in the pulleys will develop a frictional force which will cause required power transmission. Students now pause for a while and identify the design parameters. For designing the V-Belt, we require input data and that consists of type of driving unit, type of driven machine, power to be transmitted, input speed, belt velocity, belt system, either open or cross that we have to take into account, service conditions, manufacturer's data made available as standard charts, output speed and approximate center distance. These are the data we have to collect and we have to start designing. So the procedure involves determination of the load correction factor FA according to service conditions. So here it is the tested data by manufacturer is at certain different service conditions and practical applications they differ in conditions. So to account for this deviation one has to consider the load correction factor. So here I have shown in short a table which includes such factors as a standard data. So if I take an example of centrifugal pump operating for 16 to 24 hours duty, the factor becomes 1.2. So this is the way we can select from standard table a particular load correction factor. After getting the load correction factor, we can calculate the design power. So this design power is calculated as power to be transmitted multiplied by correction factor for the load that we have seen from the chart. After this we determine the cross section of the belt based on design power for which we have to consider higher speed of the shaft and design power. So this is the standard chart which is shown over here in which we consider a design power in terms of kilowatt and highest speed of the shaft. For example, if I take a 10 kilowatt power as a design and if I consider 1000 rpm of the smaller pulley then I consider this section as a P because it lies in this area of P. So my selection of standard cross section will be this help for overall economy of the belt drive. So here it is shown once again the standard cross section sizes which have been provided for different cross section. So if I say I have selected a B cross section what does it mean? It means that the trapezoidal cross section of this belt will have certain depth T and width pitch width and nominal top width. So these values have been provided in this table. And another thing is provided is that this belt has to be operated with minimum pulley diameter of smaller pulley must be 200 mm. So I am taking example of B belt its minimum recommended diameter is 200 mm. That means I should not use diameter less than this because it will add additional bending stresses in the belt and which will be unaccountable in certain cases. That's why I have to recommend one of the dimensions as a 200 minimum. Another way we calculate the diameter of the smaller pulley is D1 by considering the velocity of the belt. So many of the practical applications they use the velocity as a some standard value for overall economy and for V belt it lies between 20 to 25 meters per second. So if I accept one of these values for V I can calculate D1 from this also. So this calculated D1 with the velocity consideration and the minimum recommended diameter both must be compared and which way is higher. That diameter has to be taken as a calculated diameter and based upon that calculated diameter I have to select a standard diameter. For example my calculation goes to 42 mm then I have to select 250 mm. This is from standard so I have shown on specimen chart over here from which you can select the diameter D1 as a standard value. Upon getting this diameter D1 I go for D2 is a bigger pulley diameter. For this I have to use a speed ratio equation or velocity ratio equation shown over here. Based upon this I can calculate D2. Once again my job left is to select the standard value of D2 from the table. So this is the way I can fix the diameter D1 and D2 as a standard selection of diameter by manufacturer's data. So then I have to calculate the pitch length of the belt required. So here there are two systems as we have discussed. One is open system, one is a cross system as shown here in the figure. For open system considering the geometrical relationship as you see over here the equation is developed. So pitch length of this belt is 2 times C pi by 2 D1 plus D2 plus D2 minus D1 whole square by 4 C. So this is for open system already we are knowing D1 and D2 standard. So what left out work is calculate the pitch length. So this is the way we can calculate the pitch length for open belt system. Similarly there is a geometrical relationship for cross belt in which only the difference is it is D2 plus D1 whole square C upon 4 C. That bracket is going to change. So this is the way I calculate the required pitch length LP of the belt. However this pitch length is not available as a standard. So that's why once again we have to go for standard pitch length provided by the manufacturer data. In which I go for particular cross section I check the calculated value of pitch length and nearest to that I select the standard pitch length value from the standard data. So this is my job to select from manufacturer's data. So this way I select the standard pitch length. Now look the next requirement is that as we are going to change the pitch length than required the variation occurs. And to account for this variation once again we have to go for some correction factor and that is for belt pitch length correction factor. So if I take example of a B belt my pitch length standard calculation 1950. So I have to correct factor 0.97. So correction factor here I have to select for pitch length is 0.97. So this is the way another standard data we have to use in design. And that's why it's a correction factor for pitch length. So as we are getting a requirement of the pitch length other than calculate it it becomes necessary to go for correction in the center distance. Because we start with center distance by requirement of approximate requirement we then calculate some and then we select something. So that deviation should be accounted as a calculation of corrected center distance. So once again we are using the same equation and we are finding out the corrected center distance. Then we have to go for the calculation of angle of contact for smaller pulley. So this is the equation in which we have provided 180 degree minus 2 sine inverse d2 minus d1 upon 2c for the open belt system. So that way we can calculate the arc of angle contact arc of angle of contact for smaller pulley. Based upon this angle of contact we have to select a standard arc of contact factor. So manufacturing is testing its manufacturing data as a power rating for 180 degree angle as a standard angle. However in practical application this angle varies. So account for this variation once again we have to use arc of contact factor shown over here. So according to the calculation for example if it is 160 I have to make use of arc of contact factor 0.95. So this will be the value factor fd I have to consider in design. So the next step is to get a data about power rating of single v belt. So this is the manufacturing data made available in terms of different cross sections. So once again if I take section b belt and a minimum diameter pulley I have selected is 200 mm. So power rating of a single belt passing over this 200 mm pulley is referred as 5.23 kilowatt. So that I have to take a standard value from this chart. Making use of this standard value I can go further to calculate the number of belts. The number of belts depend upon the total design power divided by power rating of one belt multiplied by corrections factor for pitch length and arc of contact. So that is the equation we use by which we can calculate the number of belts n required for the particular practical applications. And this completes the total design procedure to select the v belt drive from manufacturers data. At the end I conclude that what we have done the procedure to find out these things. We have found out the diameter of smaller pulley d1 as a standard value, diameter of bigger pulley d2 as a standard value, belt spacing vision. For example I say that if we have selected 1950 pitch length then I can desegrate the belt as B1950 LP that way and the number of belts n and corrected center distance C. So this completes the total design procedure for v belt drive. My references are design of machine elements by VB Bandari as shown over here. Fourth edition. Thank you.