A type of solid steel axle designed without the traditional raised collars on the outer ends of the bearing journals. This design relies on the journal box and brasses to keep the axle aligned laterally. It was an early attempt to simplify manufacturing and reduce friction, but the lack of a collar made it more prone to lateral shifting under heavy loads.
Heard on the job
The shop foreman rejected the wheelset because that muley axle won't fit the new bearing adapters.
Insider tip
These are largely historic, as roller bearing assemblies require specific journal profiles that do not match the old collarless design.