行走部分 meaning in English

running gear
undercarriage

Directed by rack and guide rail which are fixed on the base , the traveling part of milling mechanism is drived by motor through feed change unit
同时，带动行走部分的大多是丝杆螺母机构，滚珠丝杆等，而光杆和齿条齿轮机构均为导向定位作用。
The link and length track is similar to the main vehicle track that again looks better fitted than it does on the sprues with little hassle during assembly
拖车的行走部分很简单，一个连接杆连两个路轮，再连到单独开出的轴上，装完后悬挂可动（动个鸟！半拼接履带！）