Originally Posted By: Ducked
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
"the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas..."
Trying to picture how that would work, and can't.
Lets say a particle is small enough to get into the oil pump, but arrives somewhere where its too big. Anywhere it arrives it seems likely to be a problem, either due to blockage, abrasion, or both.
For example, say it gets to a bearing but is too big to enter. It can be too big only because it is in contact with a rotating shaft jourmal surface, and it is partially blocking the oilway where it enters the bearing. This does not seem a benign situation.
The particles that are too large to go through a running journal bearing clearance (which is around 5 to 10 microns oil film thickness when the engine is running) probably get spit out the sides of the bearing. Since the particle isn't being "smashed" between two surfaces, then it probably isn't going to cause much if any damage.
That doesn't appear to make much sense.
If they are small enough to "get spit out the sides of the bearing", then they don't seem to be "too large to go through a running journal bearing clearance" and if they are only just small enough to "get spit out the sides of the bearing" then they are exactly being "smashed" between two surfaces".
If they are too big to enter the bearing at all then they are going to block the oilway.
That said, I don't think I've any quarrel with what seems to be the main message (filtration GOOD, dirt BAD) though I havn't read it carefully.
Here's a figure of what a journal bearing looks like when in operation. The minimum clearance (hmin) is going to be around 5~10 microns. Near the top of the bearing where the oil supply comes in will be around 40~50 microns (the bearing oil feed hole will be large, like 3~4 mm). If a particle makes it into the bearing that is larger than hmin, it won't be able to go through (get smashed in) the minimum clearance, but will most likely get carried out of the bearing via the side leakage and not really cause any damage. Obviously, you'd want an oil filter that can filter out at least most of the 40~50 micron particles.
Originally Posted By: ZeeOSix
Originally Posted By: Ducked
"the threat they pose is diminished since they are still larger than many of the clearances within an engine. Their size will not allow them to enter the contact areas..."
Trying to picture how that would work, and can't.
Lets say a particle is small enough to get into the oil pump, but arrives somewhere where its too big. Anywhere it arrives it seems likely to be a problem, either due to blockage, abrasion, or both.
For example, say it gets to a bearing but is too big to enter. It can be too big only because it is in contact with a rotating shaft jourmal surface, and it is partially blocking the oilway where it enters the bearing. This does not seem a benign situation.
The particles that are too large to go through a running journal bearing clearance (which is around 5 to 10 microns oil film thickness when the engine is running) probably get spit out the sides of the bearing. Since the particle isn't being "smashed" between two surfaces, then it probably isn't going to cause much if any damage.
That doesn't appear to make much sense.
If they are small enough to "get spit out the sides of the bearing", then they don't seem to be "too large to go through a running journal bearing clearance" and if they are only just small enough to "get spit out the sides of the bearing" then they are exactly being "smashed" between two surfaces".
If they are too big to enter the bearing at all then they are going to block the oilway.
That said, I don't think I've any quarrel with what seems to be the main message (filtration GOOD, dirt BAD) though I havn't read it carefully.
Here's a figure of what a journal bearing looks like when in operation. The minimum clearance (hmin) is going to be around 5~10 microns. Near the top of the bearing where the oil supply comes in will be around 40~50 microns (the bearing oil feed hole will be large, like 3~4 mm). If a particle makes it into the bearing that is larger than hmin, it won't be able to go through (get smashed in) the minimum clearance, but will most likely get carried out of the bearing via the side leakage and not really cause any damage. Obviously, you'd want an oil filter that can filter out at least most of the 40~50 micron particles.