As a corollary to the Steam Piston Ring thread, I've been asked "Why were sectional rings developed?". I don't know the answer myself and with the good discussion going on I thought I'd pose it to all here..............MLD

No ideas? ...Bump...mld

Single snap rings wear the bore oval, while sectional rings wear the bore round(er).
Steve

American Hammered developed a peening machine to provide variable tension around the circumference of one-piece rings in the 1910's. This technique was done by hand considerably earlier than that. The result is that when you look at the unrestrained ring it is egg-shaped being a smaller radius at the splitline and larger opposite from it. It is possible to make a ring with these characteristics by laser cutting/ cnc milling which is what they do today for large ship engine rings.

If you don't have a piston or valve that comes apart at the ring grooves, a sectional ring is the practical solution for a heavy cross-section gray iron ring or a bronze ring.