Postby Hasbeen » 02 May 2016 16:01
For what it's worth, I do believe that Spyder's description of the thing as a worry gauge is right. I have 3 times had big end bearings run in engines I was driving, [not engines I have built I might mention] & not once did the oil pressure gauge show any drop in pressure before or even during the event.
One Cosworth Ford F2 engine lost power. I pulled into the pits as I figured it was terminal. The owners crew looked at the gauge, [showing 65 PSI at 2200 RPM idle], listened to the thing, [very hard with an open exhaust], & sent me back out. I got about a mile before the rod ventilated the block.
On strip down, the steel backing of the slipper was welded into a complete ring, & hammered down until it formed a U shape around the side of the rod. The area was black, covered in carbon from the burning oil. The oil pressure did not drop at all. Another Cosworth had welded the bearing shell into a solid ring around the crank, with both the rod & crank bright blue from the heat, but again no loss in oil pressure.
The Brabham Recpo F1 engine threw a rod out through the rather expensive magnesium alloy block, again with no loss of oil pressure. I did not see the cause of that one, as Repco had built that engine & got it back for a warranty claim. They told no one why it failed.
In fact I have never seen an engine saved by an oil pressure gauge warning of impending doom. They may tell you that an old worn out Rover V8 is fit only for the scrap merchant, by showing virtually no pressure at idle, but I've found they often run for years like that, & have quite a few other ways of telling you they are about to stop.
I don't recall ever looking at an oil pressure gauge on any of the piston engined aircraft I've flown, including the mighty Sea Fury. The one we worried about was oil temperature. We were not allowed to move one with less than 70 degrees oil temperature, & were instructed if it went over 150 degrees, to either shut the thing off, & glide to a landing if possible, or prepare to jump out of the thing.
I must admit I used to wonder how much they would worry about our oil temperature, if we were at war, & the carrier was about to be attacked, but as a callow youth, I was never game to ask. What a wimp I must have been.
Hasbeen
PS. If you have a Rover, with a gauge telling you it has virtually no oil pressure at idle, remember STP is your best friend.
Hasbeen