Reasonable structure carrier should be light weight, rigidity, ease of processing and assembly. The common form of bilateral board monolithic structure, bilateral and unilateral split-plate panels of three. Bilateral monolithic plate rigidity. If this structure as a whole is forging a large amount of cutting, casting and welding methods so it can get close to the structure and size of the finished rough, but it should be taken to remove the casting or welding defects and internal stress, otherwise it will affect the strength of the carrier, processing deformation may occur when the quality and use. Bilateral board split-complex than the overall structure is mainly used for transmission is relatively small. At this planet because of a smaller diameter wheels, wheel bearing planets tend to be mounted on the carrier side wall, so that the carrier inside diameter greater than the diameter of the addendum circle; aperture center is less than the carrier side of the sun gear