Question

Figure Pl 1-12 shows an oil field pump mechanism. The head of the rocker arm is shaped such that the lower end of a flexible cable attached to it will always be directly over the well head regardless of the position of the rocker arm 4. The pump rod, which connects to the pump in the well casing, is connected to the lower end of the cable. The force in the pump rod on the up stroke is 2970 lb and the force on the down stroke is 2300 lb. Link 2 weighs 598.3 lb and has a mass moment of inertia of 11.8 lb-in-see2 (blob-in2); both include the counterweight. Its CG is on the link centerline, 13.2 in from O2. Link 3 weighs 108 lb and its CG is on the link centerline, 40 in from A. It has a mass moment of inertia of 150 lb-in-see2 (blob-in2). Link 4 weighs 2706 Ib and has a mass moment of inertia of 10 700 lb-in-sec2 (blob-in2); both include the coun 1-20 erweight. Its CG is on the link centerline where shown. The crank turns at a constant 36.9 B-CG4 32.00 B 51.26 156.6 P-CG4= 124.44 counter- weight CG4 head end O4-CG4 79.22 View as a video http://www.designof- 80 machinery.com/DOM oil pump.avi 14.03° Y 47.5 47.5 cable 14 counterweight pump rod well head FIGURE P11-12 Problems 11-20 to 11-23 An oil field pump -dimensions in inches speed of 4 rpm CcW. At the instant shown in the figure the crank angle is at 45° with respect to the global coordinate system. Find all pin forces and the torque needed to drive the crank for the position shown. Include gravity forces because the links are heavy and the speed is low. 76

Answer 1

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Рзy 1Tg - 34 MGaryFaLf (ma.aaFa).ALp - O 0 O ооо

RCF 327 b 223 bp F x - 2682 ( 2086 L F2y Fsy dT 8 ¢b]- 301LP F4y