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On 21 Jul 2003 08:03:06 -0700, (basskisser) wrote:

(Steven Shelikoff) wrote in message ...
On 18 Jul 2003 04:15:08 -0700, (basskisser) wrote:

(Steven Shelikoff) wrote in message ...
On 17 Jul 2003 11:06:03 -0700, (basskisser) wrote:

(Steven Shelikoff) wrote in message
Again, I ask a simple question. If the rings, on a properly broken in
engine seal well enough to keep molecularly small exhaust gases from
getting INTO the crankcase, at a pressure of approx. 100 p.s.i., how
in the HELL does something molecularly larger (oil) make it through
the same rings at a third of the pressure? How?

Because the pressure of the oil against the rings as they are moving
down the cylinder wall is many times greater than 100 psi. And because
oil molecules tend to stick together in a thin film. That's one of the
properties that makes oil a good lubricant. What will really blow your
mind when you think of it is that oil can get past the rings on the
power stroke, where the pressure in the cylinder is much greater than
100 psi. However, the pressure against the rings from the top is
nowhere near as high as the pressure in the cylinder due to the tight
clearance between the piston and the cylinder. If the rings had to face
the full pressure of the combustion gasses in the cylinder (as the would
if there was a lot of space between the piston and cylinder) they could
never do their job of keeping combustion gasses out of the crankcase.
As it is, they only have to seal against the small amount of gasses that
make it between the piston and the cylinder.

Steve

Okay, here we go. You are now claiming that the pressure in the
crankcase, at the time that a piston is moving down the cylinder, is
"many times greater than 100 p.s.i.????? Are you just plain flipping
NUTS? Let's say it's an eight cylinder motor, okay? Using YOUR
analogy, then, with eight cylinders, there is almost always a cylinder
moving "down". SO, just how many times 100 psi should my oil pressure
gauge show? Should it be 500 psi? 600psi? Now, because it is
essentially ONE vessel ie: the crankcase, there can not be a
differential in pressure, so don't even try it. That would be akin to
saying that the pressure is different in one side of an air compressor
tank than it is in the other side. NOT.

Somehow, I knew you wouldn't get it. Well, I know I shouldn't do this
because proving you wrong has just gotten to be a dangerous exercise.
But I'll leave you with a few thoughts:

First, do you think your oil pressure gauge is reading the pressure of
the oil against the rings as they are moving rapidly down the cylinder
wall? or do you think it is reading the pressure at the oil pressure
gauge sensor? Do you think the pressure the oil is under is constant
everywhere in the engine? i.e., do you think it's under the same
pressure when it's between the crankshaft and the rod with the rod
pushing down on the crankshaft as it is dripping down from head back
into the crankcase?

And second, we'll take your hypothetical air compressor tank and attach
a hose to the tank that's only, say, 0.05 inches ID and 100 feet long
with the far end about 5% open to simulate the efficiency of a set of
rings. Say there is 100 psi against the walls of the tank feeding the
hose. How much pressure do you think there will be against the
restrictor at the far end of that long, tiny hose? Remember, the tank
and all the hose really is one big continuous vessel. Do you really
think the pressure is constant against the walls everywhere in that
vessel? Do you really think the 95% restrictor is seeing the same 100
psi against it at the end of 100 feet of 0.05" hose as it would be
seeing if it were right at the outlet of the tank? I HOPE you say no.

Hell, an even simpler case: You have 2 garden hoses, both 100 feet long
and both with the same type of sprinkler head on each. One hose is 1"
think and the other is 0.001" think. Turn on the valve and let the same
water pressure into the hoses. Which one do you think will have more
pressure at the sprinkler when you open the sprinkler? Or do you think
both sprinklers will have the same pressure behind them?

Now, there is the EXACT same amount of pressure of the gasses on the
rings, in pounds per square inch, as there is on the top of the
piston. VERY simple physics.

Maybe TOO simple physics. Yes, definitely TOO simple physics. You're
thinking in the static case when the situation we're talking about is
dynamic. I realize that's probably too much of a stretch for you.

Now that I've proven you wrong yet again, are you gonna come after me
and hunt me down?

Steve

I said I would hunt you like the cur dog that you are, if you make
statements about my daughter, understand? I said nothing about it
being dangerous!
Now, yes, simple physics. Pressure is pressure. You are getting
pressure confused with volume. Think of what you are implying here. It
is the same as saying that the PISTONS are responsible for making
crankcase pressure. Now, again, I'll use a very simple analogy. Let's

Not at all. I don't care where the pressure came from. It could be
pressure during the compression stroke. It could be pressure from the
expanding gasses of combustion. And I'm not getting pressure confused
with volume at all.

take an air compressor, with tank. Let's say it's capable of 200psi.
With me so far? Doubtful, but we'll continue. Now, does this mean that
every time the piston pushes air INTO the tank that the air is @
200psi? NO, the air is the same pressure as the tank pressure. Now, I

Well, typically, no it's not at the same pressure. It would be if the
piston was directly attached to the tank. But usually, the compressor
and the tank are two separate "things" connected with a pipe or hose.
The pressure inside the compressor during it's compression stroke is
typically higher than the pressure in the tank. If not, then the air
wouldn't flow from the compressor cylinder to the tank.

know that your sitting there saying that's impossible. Here is where
the volumetric change comes in. The pressure changes with the VOLUME
of air being pushed in. That compresses it. Period. Same with a water

Which is completely different than an engine during a power stroke. In
that case, the pressure changes without the volume changing. The
pressure change then causes the volume to change as it pushes the piston
down the cylinder. You're simplemindedness is showing again.

pipe. Pressure starts out at 60 psi, and if the pipe is level, comes
out very close to starting pressure. The only reason that the pressure
drops a tad is because of friction from the inside of the pipe, as
well as, with the pipe not being completely smooth, laminer flow isn't
possible, it becomes turbulent. Point is, again, in a vessel (this

Ah! You're finally starting to understand why the pressure at the rings
is less than the pressure in the cylinder. Friction, turbulent flow,
etc. So you actually believe that there is smooth turbulent flow with
no friction from the main part of the cylinder to the top of the rings
when the rings are "protected" from the cylinder by the tiny gap between
the piston and cylinder? Dream on.

case, a crankcase) pressure is equal on all sides.

Never mind the fact that the pressure on the sides of the crankcase is
not equal everywhere due to turbulence and vortexes inside the
crankcase. In this case, we're not talking about crankcase pressure at
all. We're talking about the pressure of the oil against the underside
of the rings as the rings are moving down the cylinder. Pressure on the
walls of the crankcase has little to do with it because it's a tiny
fraction of the total pressure the oil exerts against the rings.

For instance, say there was no crankcase and that all you had was a
cylinder open at both ends with a piston with rings in it. Now say also
that the cylinder was coated with oil. If you pull the piston down the
cylinder, the rings are going to try and push away that oil. The oil,
being a viscous fluid that doesn't like being pushed away, is going to
exert force, i.e., pressure against the moving rings without there being
*any* crankcase pressure at all, since there is no crankcase to build
pressure in.

A force that is "many times" more than the 100 psi or so from the
combustion chamber? Haahaaahaah!!!!!

That's all you had to say? Your silence speaks volumes.

BTW, which force are you laughing at? The pressure in the cylinder
during combustion or the pressure of the oil against the underside of
the rings as they are moving down the cylinder? They're both many times
greater than 100 psi.

Are you now saying that the pressure is GREATER because of Turbulence?
Hmm, aviation engineers should try that. The work very hard to make
the air flow over wings in a laminer flow to produce greater pressure.

You should probably learn to read a little better. I said that the
pressure against the top of the rings is less than the pressure in the
cylinder. You've already stated that's impossible. But you were wrong
yet again. Now you're finally starting to understand why you were wrong
.... maybe. We'll see.

Steve