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Double horse-head pumping unit, being one of the most classical mechanical equipment, has high efficiency and good balance ability during the oil extraction owing to its horse-head structure connecting with the rod by the steel wire rope. But its characteristic of energy consumption reduction is limited because of the motor torque fluctuation and negative torque appearing while the pumping unit is working in the upstroke and downstroke. The compound balance design is applied to the double horse-head pumping unit by the crank balance and walking beam balance, which is completed by the equal energy principle during the up and down circulation of the oil suction unit. The finite element model of the whole equipment is built, and the simulation analysis is completed by the software ADAMS, under the conditions of the compound balance and that of the crank balance. The output torque of the crank, the forces from the back horse-head rope, and the connection pin are calculated. From the viewpoint of system design to compare with the traditional crank balance pumping unit, the compound balance design can reduce the torque fluctuation greatly, decrease the forces of steel wire rope connecting with the back horse-head, and get rid of the structure problems from the traditional pumping unit. The stress test of the double horse-head pumping unit designed by the compound balance method is completed in the oilfields. It has proved the correctness and reasonability of the compound balance design. The methodology of the compound balance design is helpful in improving the work efficiency and reliability and bringing about better abilities of energy consumption reduction for the pumping unit during its work circulation.

Metal rubber is one kind of elastic cellular metal material, which is widely used in vibration isolation environment for its excellent properties of elasticity, energy dissipation, and environmental adaptability. However, the stiffness range of one single metal rubber is restricted, which limits its ability of vibration isolation, especially under the complex vibration loads. In this paper, a method of spatial overlay combination is presented to widen the range of the stiffness of metal rubber material. The contact behavior of the metal spiral rolls and the influence factors of manufacture to the stiffness are investigated according to the micro-spring theory and the energy dissipation theory. The static tests under cycling loading are conducted to obtain the average stiffness and the equivalent stiffness of the combined metal rubber. After the comparisons, the combined metal rubber has a better stiffness range than the individual element. The diameter of metal wire and the relative density of metal rubber are two important influence factors to the combined stiffness, which are verified by the experimental tests and finite element simulation.