This should be a fairly easy one for a number of people here to answer. 
Over on another forum they got into discussing the engine oil filtering system on the old Allis chalmers B tractors which use a bypass type oil filter system. I tried explaining what is really going on with they design only to be told I don't understand plain english after given a numbers and basic physics based explanations regarding as to how to fix the problem bad ~70 year old design that's fussy about what oil filter is used.
http://www.allischalmers.com/forum/forum_posts.asp?TID=128490&title=b-oil-filter-experimentSo here's the problem.
The original design uses a bypass oil filtering design that basically just taps off of the main oil supply to the engine and dumps some of the oil through a 1/16" dia restrictor orifice then through the oil filter which then dumps right back into the oil pan.
The problem is this.
The original design used a highly restrictive oil filter in series with the orifice to keep from draining too much oil away from the engine lubrication system which needs to work at ~15 PSI.
The issue is that when a newer design of oil filter is used that does not have the high internal restriction the oil pressure will drop down to ~7 PSI when relying on the restrictor orifice alone which apparently does damage to the engines due to lack of proper lubrication.
Given basic orifice flow Vs pressure calculations I came up with the 1/16" orifice has a bypass flow rate of ~.5 GPM which as they say drops the system pressure down to ~7 PSI when a low restriction oil filter is being used. So if the pressure drops to 7 PSI then that would indicate the the maximum flow rate it can support is ~.25 GPM.
Which means in order to keep the system pressure up at 15 PSI the flow rate has to stay under .25 GPM and to do so the original orifice would need to be reduced by approximately half its area which works out to ~.045".
As far as the actual filter designs I have no idea and apparently neither else other than 'more restrictive must equal better filtering numbers' of which no one has any clue as to what they may be either in terms of actual micron ratings so as far as anyone knows their 'good filters' could just as well be completely blocked off and provide no filtering whatsoever but do keep the oil pressure up. 
That seem rational because over they apparently I am a big fool who doesn't understand basic english and worse. 
And yea I invited them over here to play with the rest of us fools hoping someone will bring some real workable information with them.
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