1Prepared by: Ferhat Sağlam Room: C-210 Phone: 5267 E-mail: [email protected] SPRING 2012 Date: 24.05.2012 ME 308 – MACHINE ELEMENTS II TUTORIAL 9 “Design of Chain Drives” Problem 1: A roller chain is to transmit 60 kW at a speed of 500 rpm. Reduction ratio is 3. Driven machinery may cause heavy shock loads while the driving motor has normal torque characteristics. Center distance should be within and chordal speed variation should be 1.5%. Design the power transmission system. Problem 2: In a roller chain drive, chordal speed variation should be less than 1.3 %.and the center distance is to be adjusted within Reduction ratio of the chain system is 4. Determine: a) pitch diameters of the sprockets b) the chain length c) exact center distance Do not use offset link. METU – ME 308 Machine Elements II – Spring 2012 chain-140 is of lubrication type C which requires oil-stream lubrication since it needs a sophisticated lubrication system. Load service factor. Multiple strand factor. Center distance can be found by using the following equations: [ √ ( ) ] and Then. Let’s try to have a solution using a single strand first. .Problem 1 Solution: For smooth operation at moderate and high speeds it is considered good practice to use a driving sprocket with at least 17 teeth.8 kW. . for two strands. or approximately: ) ( ) ( For . This can be achieved by increasing the strand number and therefore reducing the required rated power capacity of the chain. chain with ISO(ANSI) Type C #140 is appropriate where Htab=85. and the teeth ) ( ) ( ) ( ) Similarly. Using 19 or 21 teeth will. Allowable power can be written as: The factors in this equation can be obtained as follows: Tooth correction factor. for heavy shocks from Table 17-15. Minimum rated capacity for the stated power transmission: [ √( ) ( ) ] Pitch diameters of the sprockets: ( ) ) ( ( ) ) Referring to Table 17-20 with the sprocket speed 500 rpm. From Table 17-19 for chain #120 The pitch for the sprockets: Center distance range can be used to determine the length of the chain: METU – ME 308 Machine Elements II – Spring 2012 . From the chordal speed variation: [ ( ]. . the teeth number of the driving sprocket can be selected as number of the driven sprocket will be . give a better life expectancy with less noise. of course. Therefore use 2 strands chain drive. 68 or 69. it is advised to have even number of pitches in the chain. It would be better to use a type-B chain for which bath lubrication is sufficient. ( Then ISO(ANSI) type-B 120 is appropriate for this case where Now we can proceed to determine dimensions of the components. So. . . for one strand from Table 17-23. But when speed is 500 rpm. In order to avoid a special link. ( ) ( ( ( ( ) ) ) ) 2 The number of pitches can be 67. for from Table 17-22. is selected. . 35 9.01 195.37 124.30 167.04 102.05 25. ( ) ( ) Chain Number 25 35 40-41 50 60 80 100 120 Pitch. Then. ) and ( a) ( ( ) ) ( ( ) ) METU – ME 308 Machine Elements II – Spring 2012 . [ Since center distance is given in a very tight range all available pitch diameters for a chain ) ratio should be used.71 244. chain size 40-41 is chosen. p[mm] 6.02 ) and ( ) √( ) ( ) ] (L/p)max 340. drive should be tried and one that gives even integer ( Then.3 Problem 2 Solution: From the chordal speed variation: [ ( ]. are found.96 167. Therefore. or approximately: ) ( ) ( For . and the teeth ) b) ( ) .08 244.70 15.57 148. can be constructed. by using the following formula and Table17-19.12 As seen from the table only two possibilities.52 12.10 (L/p)min 340.88 111.88 19.43 196. the teeth number of the driving sprocket can be selected as number of the driven sprocket will be .32 148. . which give integer (L/p) ratio.40 31.60 125.04 111.16 102.75 38. as found before c) Exact center distance can be obtained by using the above information [ √ ( ) ] and Then. Since it does not require using of an offset link one should take even integer (L/p) ratio given in the third and fourth columns. a table of ( for each available pitch value.