An object of the present invention is to provide a motor control device capable of estimating a delay with high accuracy even in a case where there is a fluctuation in disturbance torque or delay time and of suppressing the influence of the delay. For this end, the present invention includes a motor MTR, an ECU 2 that controls the rotation of the motor MTR, and an ECU 1 that sends a torque command to the ECU 2 based on a command value. The ECU 1 includes a disturbance estimation block 100 and a delay estimation block 200. The disturbance estimation block 100 estimates disturbance torque (?d) using a torque command input to the ECU 2 and a feedback value of the motor MTR. The delay estimation block 200 estimates a delay using a torque command output from the ECU 1, the feedback value of the motor MTR, and the disturbance torque (?d).

An assembly is used to connect an equalizer bar to a walking beam of a reciprocating pump unit. The walking beam has a bearing shaft having cylindrical ends. Brackets attached to the equalizer bar define slots, each having a hooked section and having a base section. The hooked sections are configured to rest against the cylindrical ends of the bearing shaft. The base sections of the slots oppose the hooked sections at a gap from the cylindrical ends of the bearing shaft. Wedges are configured to position in the slots between the bases and the cylindrical ends of the bearing shaft.