push mower engines,,, how are bearings sealed?

[Doug4d3s]

While sketching out some ideas for the engine project I am wanting to attempt, I got to the point of planning out how much room to leave for engine bearings.... Then I got to wondering what kind of bearings to use exactly, to make sure the engine oil stayed inside the engine.

I have seen flanged bearings (online) that are sealed on the flange side only, but I've also bought a few double-sealed bearings and observed that the shields/seals often didn't really "seal" them so much as help a lot in keeping the grease in and dust out.... you could wiggle the inner race and see space open up between the seal and the races.

The engine I am planning is a horizontal-shaft and the crankcase oil level will be below the bearings--so the bearing seal doesn't need to hold back liquid pressure, but it does need to keep the oil inside as well as reasonably possible against splash lubrication. Will just any flanged/single-sealed bearings work for this, or is there something special I should be looking for?

And while we're here,,, how does a vertical-shaft lawnmower engine seal the lower bearing? Is the silicone seal the only thing holding the oil inside? Or a metal seal? Or maybe, is the bearing inset enough that oil just doesn't pool around it with the engine sitting in its normal position? I've only ever seen a couple lawnmower engines taken apart in my whole life, and that was many years ago. And I know what will happen if I take mine apart just to look....

[dly31]

Most of these engines use plain bearings, either running directly in the aluminum crankcase or with a bronze bushing. Regardless of bearing type, the oil sealing is not part of the bearing. They use conventional lip seals outside of the bearing in both the top and bottom. The vertical crankshaft models have a long boss inside the lower crankcase that keeps the crankshaft and top of the bearing above the oil level. You do not want the crankshaft to be immersed in the oil regardless of its orientation. A small dipper to splash the oil around is normally attached to the connecting rod cap on horizontal crankshaft models. Vertical crankshaft models commonly have a similar dipper driven from the camshaft.

Ball or roller bearings have to be fairly substantial to stand the vibration in an engine and I think plain bearings would be much preferred.

Nearly any mower shop should have plenty of junk motors for you to look at.