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By some fairly simple modifications to the "8 lobes in 9' (trochoidal) type of oil pump it can be made to function as several independent positive displacement pumps. Have a separate. "pump" supply oil to the valve gear. Have a separate "pump" and supply line for each main bearing etc.. With this
scheme even if a bearing becomes worn to the point where its clearance offers almost no resistance to the oil being pumped to it the other parts of the engine will still get oil.
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Current manufacturing processes are so good that such add-extra-cost redundancy/protectant systems are, on any engineering analysis, quite unnecessary. Where the situation warrants, e.g. in large marine engines, dedicated oil pumps for individual components are already the norm. |
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In your system, if other parts of the engine are still getting oil and oil is still circulating and cooling the system generally while one component is breaking down, isn't that more dangerous and likely to cause more damage (the operator is unaware of building pressure / temp and there is eventually a catastrophic failure of the distressed bearing/rocker/rod/etc)? |
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[Consulf] The extra cost of this feature would not be much. I think the largest cost would be for the individual pressure relief valves and oil pressure sensors. In the long run this feature would add much value to the product.
IIt seems a little contradictory to say that where the situation warrants (marine engines - large marine engines that is) this is the norm but that the same feature could be dangerous because the operator might not realize that a part was failing. Properly instrumented this system would give notice to the operator that all was not well.
Chances are, this system would be most useful on high time engines where most or all bearings are worn. |
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My mother's old Rover (1946 P3 series) had an automatic chassis lubrication system whereby oil or grease was dispensed to the various points on the suspension, steering, etc from a central reservoir. The pump was actuated by a plunger attached to the front axle; each time you hit a bump, it would sent a little squirt of lubricant down each pipe. Each section of the pump could be adjusted to dispense the correct amount. |
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[UB] If your distracted driver pays no attention when the oil pressure light comes on that is too bad. With the Positive Lubrication scheme she is still more likely to get the kids to the soccer game with no pressure on one bearing.
I presume that one of those humongous multi-million dollar marine engines with perhaps 80,000 shp is fully instrumented with alarms and a repeater on the ship's bridge. Guys with clipboards climbing around the engine would not be the usual way of keeping tabs on the health of the ships powerplant. |
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[Consulf Laminiscus] It's been my experience that when a bearing is going bad you can eventually hear it knocking, thudding or clicking away. Ignore your engine long enough and something will break. With a scheme where lubrication continues despite wear you may have more time to realize that something is wrong and do something about it, or conversely, you may just have a longer time to ignore the engine's distress. Whether or not you ignore the noise you have a longer service life, . |
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Suppose the clearance of your main bearings increases to the point where oil pressure is near zero. This is not a part breaking down but is simply the normal wear of moving parts. The main bearings are still being lubricated even if their clearance is large and since they are being lubricated, the rate of wear of these main bearings may still not be very high. However, without a positive source of lubrication the parts higher in the engine such as the cam, hydraulic valve lifters etc. will be starved of oil and rapidly fail. When the engine becomes excessively noisy or stops running due to these other, higher parts failing the mains and rod bearings may still be good even if their clearance is larger than normal. Wouldn't it be better to keep all of the parts lubricated so the engine can continue running satisfactorily for as long as possible? |
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One thing to keep in mind is that at the moving parts having oil there is what is important -- not what pressure it is under. Moving parts are not kept apart by hydraulic pressure but by the film of oil between the surfaces. |
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Which is why to tight is worse than to lose when you rebuild. I used to hate Plastigauge untill I realized that it was actually a pretty good model for how the bearing would lubricate. |
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Impossible to replace without disassembly of the engine (-). Does not fix the need for drilled oil passages in the crank (-).
Suction rather than pressure through the filter (-). |
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By the time you are losing all oil pressure through the crank journals the time for an overhaul has long passed. |
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[WcW] The oil pump envisioned would
not be a replacement. To use this
several-pumps-in-one there would
need to be separate oil galleries going
from their portion of the pump to a
main bearing or a different main or to
the cam/valve gear.
To retrofit it new lines would have to be
installed and plugs placed in existing
oil galleries drilled in the block. |
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Ok then here is my question: Where does this extend the life of the engine? The bearings will still wear as normal and, when they are worn out they will need replacement. You only really gain engine life if you improve lubrication at startup and prevent lubrication failure while running. The redundant pumps are worthless if you realize that a significant failure of one or all of the pumps, one or all of the bearings, and any other critical example of wear means a rebuild. |
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Simply putting a larger pump in place will adress the problem that you seem to be trying to solve. Some loosely built turbocharged engines run a larger pump and do just fine over the life of the other engine componants. |
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[WcW] Old way: The more a bearing is worn the more oil it gets. The oil in excess of what is needed for lubrication goes back to the sump and what's left goes to the less worn bearings. More oil doesn't help the worn bearing wear less but less oil to the other bearings will make them wear faster.
Positive Lubrication way: All bearings get the amount of oil they are designed to get. |
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