Tony Rhodes wrote:
> Message text written by INTERNET:triumphs-owner@autox.team.net
> " As liquids (including oils) are generally considered to be not compressible
> materials, the pressure in the oiling system should be constant throughout
>the system."
>
> Brian, I hate to disagree with you here. Yes, oil is essentially
>incompressible, but
> that does not mean that the oil system must be at the same pressure
>throughout.
>
> Think of your garden hose. Your tap has 20 or 30 psi going to it. Now you
>open it
> part way and let the water flow freely from the open end of the hose. What
>is the
> pressure of the water at the open end? Not much. What is the pressure behind
> the tap? 20 or so psi.
>
> I would agree that BEHIND the flow limiting orifice, the pressure is
>constant. After
> that orifice, the pressure may well be very low.
I don't think we're disagreeing at all. That really was my point, that the
bearing is the faucet
and behind the bearings the pressure delivered to each bearing would be equal
making it irrelevant
where the pressure gauge tap was located.
I've been contemplating what Michael said about pumping losses and restrictions
governing pressure
at certain points in the system, but can't seem to rationalize it. I keep
coming back to an
engine in poor condition, say one with a rod knock. I've never seen an engine
with a rod knock
that had good oil pressure on the gauge. If it were true that system pressure
varied from one
bearing to another, only the bad bearing would have low pressure and the gauge
should register
the rest of the system pressure as OK, unless the bad bearing was the one
opposite the gauge tap.
This I have never seen before.
I suppose the debate is somewhat philosophical as to when the pressure
transitions from the high
pressure of the oil gallery to the low pressure of dripping out of the
clearance in the bearing.
Having had the luxury of pressurizing an oiling system without the oil pan on,
I can say that the
oil doesn't squirt out around the rods and mains under pressure, it just sort
of oozes out and
drips off, yet the gallery feeding the bearing registers some 50 or 60 psi.
How are we defining
pressure at the bearing? Is it at the end of the gallery just prior to the
bearing, or is it were
the oil is dripping out the bottom, or is it somewhere else in the middle?
To help me understand Michael's point about the pressure gauge tap location, I
am going to try a
little experiment on an engine slated for a rebuild I have here and see if I
can discern any
pressure differences by moving the location of the tap to different gallery
plugs on the side of
the motor. I'll report back in the next day or two with the results.
Regards,
Brian Schlorff '61 TR-4 '64 TR-4 '72 TR-6 '79 Spit
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