We are advised that white metal bearings in a Myford will 'tolerate' a bit over 600 rpm, with its drip-feed oilers.

Old car engines with similar oiling systems (a bit more oil mist, but dirty oil) will stand up to 4000 rpm and much higher out-of-balance loads. And much longer periods of continuous loads.

So – could we push our Myfords round rather more quickly?

Regards, Tim

With all due respect, Clive, can you quote examples?

The old Fordson Standard provided maximum power @1200rpm (a non-pressurised oiling arrangement). I know of some engines with pumped ‘splash’ crank bearings running up to 2200rpm with aluminium pistons (1600rpm was generally regarded as enough with cast iron pistons). All higher speed engines I have come across have had pressure-fed crankshaft bearings.

All the engines with dippers for crank lubrication were much lower-speed designs (800rpm and below?).

Was that engine fitted with plain bearings? Many Honda engines have/had roller bearings.

Yes those are the MEW issue numbers in the opening post

Drip, or splash fed plain bearings are limited in speed because of temperature factors, as well as rubbing speeds or load.

Pressure fed bearings are better at building up a "wedge" of oil, for hydrodynamic lubrication, but the increased flow is to cool the bearing. Hence, pressure fed bearings tend to run with larger clearances, to encourage a flow to cool the bearing.

On main propulsion engines on ships, bearing temperatures are monitored, rather than oil pressure.

Excessive oil temperatures degrade the oil, not that a lathe should produce localised temperatures in excess of 110C.

Over heating white metal bearings cause the composition of the bearing alloy to change, (not for the better! ) some time before they fail. Sometimes, the constituents start to separate out.

For really high speeds, such as automotive turbochargers the bearing are actually sleeve bearings where the sleeve is white metal coated on both internal and external faces. In this way, the sleeve rotates and the rubbing speed relative to the shaft and to the housing is decreased.

Howard