桅杆起重机,是一种简单的起重设备。桅杆本身通常采用园木制成,对制作桅杆的木材要求较高,如质轻、强度大,长而平直等。多采用杉木,但符合上述要求的杉木一般也很难找到,即使有,也是价格昂贵、运输,保存都不容易。桅杆也可用四根型钢或钢管用撑条焊接组合而成(又称金属格构式起重桅杆),这种桅杆起重能力较大,结构也合理,但往往因材料来源困难等原因而无法采用,对于材料和经费都较困难的小型水利工程,各种规格的钢 Mast crane is a simple lifting device. The mast itself is usually made of garden wood, which requires high requirements for the production of wood, such as light weight, high strength, long and straight. Most of them use fir, but the firs that meet the above requirements are generally difficult to find. Even if they are, they are expensive and they are not easily transported. The mast can also be made of four steel or steel bars brazed together (also called a metal lattice lifting mast). This kind of mast has a large lifting capacity and a reasonable structure, but it is often impossible due to the source of the material and other reasons. Adopting small-scale water conservancy projects that are difficult for materials and funds, various specifications of steel