选择起重机人字架顶点和前、后撑杆在平台上的位置(图1所示,确定C、O_2、O_2三点位置的四个尺寸x_1、x_2、x_3、x_4),是绳索变幅的单臂架类型起重机总体设计时要遇到的问题,也是大家正在探讨的问题。设计实践表明,如果x_1、x_2、x_3、x_4选择得比较合理,所设计出的起重机就具 Choose the position of the crane’s head and the front and rear struts on the platform (as shown in Figure 1, the four dimensions x_1, x_2, x_3, and x_4 at the three points C, O_2, O_2) are the rope amplitudes. The problems encountered in the overall design of single-arm type cranes are also issues that we are currently discussing. Design practice shows that if x_1, x_2, x_3, and x_4 are chosen reasonably, the designed crane will have