Question 11.3: Dynamic Force Analysis of a Fourbar Linkage. (See Figure 11-...
Dynamic Force Analysis of a Fourbar Linkage. (See Figure 11‑3)
Given: The 5-in-long crank (link 2) shown weighs 1.5 lb. Its CG is at 3 in @ +30° from the line of centers (LRCS). Its mass moment of inertia about its CG is 0.4 lb-in-sec². Its kinematic data are:
\begin{array}{cccc}\theta_{2} \text { deg } & \omega_{2} rad / sec & \alpha_{2} rad / sec ^{2} & a_{G_{2}} in / sec ^{2} \\60 & 25 & -40 & 1878.84 \text { @ 273.66 }^{\circ}\end{array}
The coupler (link 3) is 15 in long and weighs 7.7 lb. Its CG is at 9 in @ 45° off the line of centers (LRCS). Its mass moment of inertia about its CG is 1.5 lb-in-sec². Its kinematic data are:
\begin{array}{cccc}\theta_{3} \text { deg } & \omega_{3} \text { rad/sec } & \alpha_{3} \text { rad/sec }^{2} & a_{G_{3}} \text { in/sec }^{2} \\20.92 & -5.87 & 120.9 & 3646.1 \text { @ } 226.5^{\circ}\end{array}
The ground link is 19 in long. The rocker (link 4) is 10 in long and weighs 5.8 lb. Its CG is at 5 in @ 0° on the line of centers (LRCS). Its mass moment of inertia about its CG is 0.8 lb-in-sec². There is an external torque on link 4 of 120 lb-in (GCS). An external force of 80 lb @ 330° acts on link 3 in the GCS, applied at point P at 3 in @ 100° from the CG of link 3 (LRCS). The kinematic data are:
\begin{array}{cccc}\theta_{4} deg & \omega_{4} rad / sec & \alpha_{4} rad / sec ^{2} & a_{G_{4}} in / sec ^{2} \\104.41 & 7.93 & 276.29 & 1416.8 @ 207.2^{\circ}\end{array}
Find: Forces F _{12}, F _{32}, F _{43}, \text { and } F _{14} \text { at the joints and the driving torque } T _{12} needed to maintain motion with the given acceleration for this instantaneous position of the link.
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