I feel like this is another conversation with a politician. Why do I bother?
So for a clarification to the onlookers, let me respond in this manner.
Your original contention (or at least how I understood your point) was that forced (pumped) oil pressure was unnecessary for separating the rotating parts of an engine. My point is that forced oil is necessary in this instance, if using shell style (not ball or needle) style bearings.
I also pointed out the necessity for controlling clearances, oil film flow speed, etc.
The elements of how the film creates a wedge are all part and parcel of the function of the rotation of the parts. How much oil reaches the bearing is set by viscosity, oil system design, clearances in other parts of the engine, etc. What happens on one single shell style bearing - lets say a rod bearing - is going to be a function of the oil pressure, viscosity, clearance, rotational speed, width of bearing, side clearances, etc.
To think that this bearing system doesn't rely on forced oil as the first part of the design would be ludicrous. Without forced oil, this system could not function, well, not long enough to provide any service.
Let's also look at heat build-up on the bearing and shaft. Forced oil, flowing off the side clearances, carries away the heat. This is again another place where viscosity plays a key role. If the film is to thin, it flows off the bearing sufficiently, but the wedge thickness can be crushed by the forces applied at a given point in the rotation - think "power stroke" and you'll see what I mean. If the oil is to thick, it provided better protection in terms of separating the parts, but the slow flow off the surface results in excessive heat build up in the parts.
Crankshafts are drilled so that the bearing gets a fresh shot of oil from the system just as the highest loads are being applied through the rod. If pumped oil was really unnecessary, then why insure the highest amount of fresh, cool (relative to the parts being oiled) , pressurized oil is applied as the power stroke occurs, and that the top shell of a rod gets this oil during said power stroke?
One of the failures that can occur to engine rod bearings occurs when pre ignition takes place. Basically the piston / rod is slammed down onto the crank while the crank is still reaching or at TDC. The result isn't to rotate the crank, but hammer the rod bearing top shell into the crank. This is one place where the hydrostatic fluid wedge often gets overwhelmed and is pushed out. Bearing hits crank, and permanent damage is the result. Not just from heat but from deformation. Have you ever seen a shell bearing lose it's crush?
This happens because of the bearing being hammered into the crank, from oil film loss, not heat.
Of course, all my ramblings are moot if you take the politician's approach, and try to fall back on "the oil film strength is provided by rotational force, viscosity, etc" sure, true, to an extent - but the big problem with that theory is that if forced oil had not been introduced to the journal / bearing to start the process then the film strength from rotation, etc could never develop regardless, and therefore engines with shell style bearings rely on forced oil, period. Steve