34 you are given a set of three links with lengths 24

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Unformatted text preview: d whether they are crank-rocker, double-crank, or double-rocker mechanisms. 8" 3" 7" 6" (a) a) s + l < p + q Grashof type 1 s + l > p + q nonGrashof type 2 s = 3; l = 7; p = 5; q = 6 3 + 7 < 5 + 6 10 < 11 Grashof type 1 Since the shortest member is connected to the frame, the linkage is a crank rocker b) s + l < p + q Grashof type 1 s + l > p + q nonGrashof type 2 s = 4; l = 8; p = 5; q = 6 4 + 8 > 5 + 6 12 > 11 nonGrashof type 2 All Grashof type 2 linkages are double rockers c) s + l < p + q Grashof type 1 s + l > p + q nonGrashof type 2 s = 4; l = 8; p = 6; q = 7 4 + 8 < 6 + 7 12 < 13 Grashof type 1 Since the shortest member is the frame, the linkage is a double crank or drag link mechanism 8" 5" 5" (b) 4" 6" 7" 4" (c) 6" - 37 - Problem 1.34 You are given a set of three links with lengths 2.4 in, 7.2 in, and 3.4 in. Select the length of a fourth link and assemble a linkage that can be driven by a continuously rotating motor. Is your linkage a Grashof type 1 or Grashof type 2 linkage? (Show your work.) Is it a crank-rocker, double-rocker, or double-crank linkage? Why? Let: l = 7.2 in s = 2.4 in p = 3.4 in q = x in Coupler 7.0" 3.4" Rocker 2.4" Crank 7.3" Frame s + l < p + q ⇒ Grashof type 1 linkage 2.4 + 7.2 < 3.4 + x 9.6 < 3.4 + x ⇒ 7.2 < x Let x = 7.3 This is a crank-rocker because the shortest link is the driver. - 38 - Problem 1.35 You have available a set of eight links from which you are to design a four-bar linkage. Choose the links such that the linkage can be driven by a continuous-rotation motor. Sketch the linkage and identify the type of four-bar mechanism resulting. L1 = 2”, L 2 = 3”, L 3 = 4”, L 4 = 6”, L 5 = 7”, L 6 = 9.5”, L7 = 13”, and L8 = 9” Let: l = 9.5 in s = 3.0 in p = 9.0 in q = 4.0 in s + l < p + q Grashof type 1 9.5 + 3 < 9 + 4 ⇒ 12.5 = 13 Coupler 9.0" 4.0" Rocker 3.0" Crank 9.5" Frame Since the shortest link is the driver, the mechanism is a crank-rocker. - 39 - Problem 1.36 Determine the number of fully rotating cranks in the planar mechanisms shown below. Show your calculations. 2.25" 3" 2.5" 3" 37mm 30mm 4" 20mm 35mm 2" 2.25" 3.5" (a) (a) l = 3.0 in s = 2.25 in p = 3.0 in q = 2.5 in (b) (c) s + l < p + q Grashof type 1 3 + 2.25 < 3 + 2.5 5.25 < 5.5 Choosing l as the frame results in a double rocker with two fully rotating cranks. Choosing l , p or q as the frame results in a crank rocker of double rocker with one or zero rotating cranks, respectively. (b) l = 37.0 mm s = 20.0 mm p = 35.0 mm q = 30.0 mm s + l < p + q Grashof type 1 37 + 20 < 35 + 30 57 < 65 Choosing l as the frame results in...
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This note was uploaded on 02/20/2011 for the course MEC 411 taught by Professor Shudong during the Winter '11 term at Ryerson.

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