locomotive tractive effort

例句：

1. 1. The locomotive was the main source of power for the train.
   火车头是火车的主要动力来源。
2. 2. The engineer had to repair the locomotive before it could start again.
   工程师必须修理火车头才能再次启动。
3. 3. The locomotive was a marvel of engineering and design.
   火车头是工程和设计的奇迹。