bare universal joint

例句：

1. 1. The car's engine is a bare universal joint.
   这辆车的引擎是一个裸关节。
2. 2. The old house has several bare universal joints that need to be replaced.
   这所老房子有几个需要更换的裸关节。
3. 3. The engineer carefully checked the bare universal joints of the machine before starting the operation.
   工程师在开始操作之前仔细检查了机器的裸关节。