Ring oiler

As speeds or bearing loads later increased, forced pressure lubrication became more prevalent and the ring oiler fell from use.

The rotating ring in turn picks up some oil and deposits it onto the shaft, from where it flows sideways and lubricates the bearings.

The oil ring is effectively a simple lubrication pump, with only one moving part and no complex or high-precision components.

[1] Above this, the oil tended to be thrown centrifugally from the ring, rather than carried by it (although it is still currently applied on steam turbines with speeds around 3200 rpm[citation needed]).

Automatic ring oilers were particularly useful for large engines with multiple horizontally opposed cylinders, where it was otherwise difficult to access the central main bearings.