2.What should be the percentage increase in friction coefficient if the self-locking condition must be satisfied? 3.If the following are conditions for an effective cost design: a)At least 85% of the lining material allowable pressure should be utilized. b)The maximum operating applied load cannot exceed 1000 lb. c)The material lining width should be below 2.0 in. d)c = 12 in. Find the minimum allowable pressure of the lining material? 100 F A Rotation 130o 80 a
Problem 3: It is required to design a multiple-disk clutch-brake to transmit a total torque capacity, Tdepending on the number of disks used in it. The design considerations are: The space restrictions limit the outside disk diameter to 100 mm. Steel disks. Molded friction materials. Dynamic friction coefficient (wet conditions) f = 0.06. Maximum allowable pressure, pa= 1500 kPa. Using both uniform wear (UW) and uniform pressure (UP) assumptions, answer the following questions: a)Select an acceptable upper value for the internal diameter, d, of the disk before d/D reaches the limit where the 2 assumptions UW and UP become similar and estimate the number of disks (even number) if the total transmitted torque capacity, Tis 90 N.m. comment on the results. b)Calculate the actuation force for both assumptions. c)You are required to over design this clutch by 35%, give two available alternatives. Problem 4:A differential band brake has a specified rated braking torque of 4000 N-m. Design values for drum diameter, angle of wrap, coefficient of friction and maximum normal pressure are specified. Determine: a)A suitable width for the belt. b)The actuating force FD= 650 mm ϕ= 250o, f= 0.4, pa= 1.1 MPa a =120 mm c = 650 mm s = 15 mm .
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