# Study on the Position Deviation between the Iron Roughneck's Spin-Rollers and the Drilling Tool
## 2 Materials and Methods  
### Structure and Working Principle of Spinner Mechanism  
The working tong body of the iron roughneck includes two parts: the hydraulic main tong and the spinner mechanism. The hydraulic main tong is used to clamp the lower drill pipe and realize the punching action of the upper drill pipe, and the spinner mechanism is used to realize the rapid screwing-in or disengagement of the thread of the upper drill pipe [22]. When the spinner mechanism works, the lower drill pipe is clamped by the hydraulic main tong so that the central position of the drill pipe is determined. Ensuring the alignment between the upper drill pipe and the lower drill pipe is an important guarantee to realize the spinning action.  
The spinner mechanism is shown in Figure 1: (a) is a three-dimensional model, and (b) is a kinematic diagram, which is mainly composed of a clamping oil cylinder, cross beam, wedge plate, return spring, tangent wheel, clamping arm, column, follow-up roller, driving roller, hydraulic motor, and floating mechanism. The main characteristic dimensions of the mechanism are as follows: the length of the clamping arm AB and BC are \(L_{\text{AB}}=332\) mm, \(L_{\text{BC}}=320\) mm, and the included angle is \(\gamma_{1}=134^{\circ}\); the included angle between two sides of the wedge plate is \(\gamma_{2}=60^{\circ}\); the radius \(R_{1}\) of the driving roller is equal to the radius \(R_{2}\) of the follow-up roller, which is \(R_{1}=R_{2}=R_{\text{a}}=90\) mm; the radius of the tangent wheel is \(R_{3}=50\) mm.  
The spinner mechanism adopts the structure of three rollers, including two driving rollers driven by hydraulic motor and one follow-up roller. When it is working, the piston rod of the clamping oil cylinder extends to push the wedge plate to drive the follow-up roller to approach the drill pipe. At the same time, the two sides of the wedge plate push the tangent wheel installed at one end of the clamping arm to swing outward, and then drive the clamping arm to rotate around the middle pin shaft to realize the inward rotation of the driving roller installed at the other end of the clamping arm. This form of spinner mechanism reduces the number of clamping oil cylinders and has a compact structure. However, when working, the driving rollers and the following roller will not contact the drilling tool at the same time. To ensure that the three rollers can hold the drilling tool tightly, a floating mechanism is set between the cross beam and the column. When the roller in one direction contacts the drilling tool the contact force is generated. Due to the action of the floating mechanism, the whole spinner mechanism outside the column will move back or forth under the action of the force until the three spin-rollers completely clamp the drilling tool. When the three rollers hold the drilling tool tightly, the hydraulic motor drives the driving roller to rotate and thus drive the drilling tool to rotate clockwise or counterclockwise to complete the rapid screwing-in or screwing-out of the drilling tool thread. The return spring in the figure is used to ensure that the tangent wheel is always in contact with the edge of the wedge plate, and the two clamping arms can quickly release the drilling tool when the piston rod of the clamping cylinder retracts. The main technical parameters of the spinner mechanism are shown in Table 1.  
Figure 1: Spinner mechanism: (**a**) three-dimensional model; (**b**) kinematic diagram. In the figure: 1—clamping oil cylinder; 2—cross beam; 3—wedge plate; 4—return spring; 5—tangent wheel; 6—clamping arm; 7—column; 8—follow-up roller; 9—driving roller; 10—hydraulic motor; 11—floating mechanism.