A solid steel rod connecting the crank pins of multiple driving wheels on a steam or early diesel locomotive. By physically tying the axles together, it distributes the tractive effort from the main rod across all the driving wheels, preventing a single set of wheels from slipping under heavy load. They require precise quartering of the wheels to avoid binding or snapping the rod.
Heard on the job
The shop crew found a hairline crack in the rear coupling rod during the annual inspection.
Also heard as
- side rod