Posted by TheOldHokie on September 29, 2012 at 10:55:46 from (108.8.6.218):
In Reply to: 35PSI - Means What posted by CharnerL on September 29, 2012 at 08:01:38:
R Geiger said: (quoted from post at 13:09:43 09/29/12)
The main thing that determines oil pressure is the clearance in the bearings. Too much clearance and I don't care what oil you use there will be no pressure. Granted you need a good pump to start with but the best pump in the world will not create pressure without the resistrictions from the bearing clearance.
Precisely. And I don't care if you have 80 PSI pump oil pressure that oil pressure won't keep the journals clear of the bearings if the clearances are too wide. The journal is held off the bearing surface by a localized pressure differential inside the bearing shell that is orders of magnitude greater than pump oil pressure - well up into the thousands of pounds. That differential comes from the formation of a hydro-dynamic "wedge" of very high pressure oil (red area in the drawing) opposite the load on the crankshaft. It is produced by the journal surface dragging oil around the bearings as it rotates and compressing it in the constricted clearance opposite the load. Too much bearing clearance and that wedge won't form and the journal is forced down onto the bearing surface by the load. It is this hydro-dynamic phenomenon that allows a splash lubed lawn mower engine to maintain a bearing oil film with ZERO pump oil pressure. The three factors that affect the formation of that wedge are:
Bearing clearance
Oil viscosity
Surface speed of the journal
Pump oil pressure has virtually nothing to do with it.
TOH
This post was edited by TheOldHokie at 11:29:01 09/29/12.
We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today. [ About Us ]
Today's Featured Article - Madison's County - by Anthony West. Philip Madison has been a good friend of mine for quite some time. He has patiently suffered my incessant chit chat on the subject of tractors for longer than I care to remember, and on many occasions he has put himself out, dropped what ever it was he was doing, to come and lend a hand cranking handles, or loading a find onto a trailer. Although he himself has never actually owned or restored a tractor, he was always enthusiastic and always around helping with other peoples projects.
... [Read Article]
All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy
TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.
