Howard,
Thanks for the feedback. I agree with you 100%. Isn't that
what I said?? Or did I make some careless error of my own??
Actually I didn't mention the compression stroke at all, I don't
think. There is only a relatively small side thrust there. I was
only comparing the 2 "down" strokes, intake and power, because the
message I was responding to mentioned only "down" strokes.
Cheers,
Dave K.
-------------------------------------------------------------------
>Hi David,
>It does muddy the water as it is wrong. The thrust face is forced
>against the cylinder wall much harder on the power stroke than on
>the compression stroke. Ask any piston manufacture. I was "Product
>Information Manager" for a major piston manufacture and at times
>handled the liability claims for two major engine parts manufactures
>and Importers of import car parts and had to examine many failed
>pistons for evaluation of cause.
>
>Howard Fitzcharles
>
>-------Original Message-------
>
>From: <mailto:dkern@napanet.net>David Kernberger
>Date: 3/25/2009 6:27:04 PM
>To: <mailto:mgb-v8@autox.team.net>MG
>Subject: Re: [Mgb-v8] [!! SPAM] Re: Ah, the details........
>
>IS this still an unanswered question? In case it is, I will give it a go.
>
> By convention a down stroke is when the piston is moving
>towards the crankshaft (ie POWER and intake strokes) and an upstroke
>is when the piston is moving away from the crankshaft (ie compression
>and exhaust strokes). During the power stroke the force of
>combustion is downward (toward the crank) on the piston but the
>upward resistance offered by the connecting rod and crankshaft is
>partially sideways because the rod is at an angle. The result is the
>piston is jammed against one side of the cylinder more forcefully
>than the other. That side is the thrust face.
>
> Therefore, as stated below, the small end of the rod will
>always point toward the thrust face whenever the piston is on a
>downstroke. But it is only on the power stroke that there is enough
>force for it to matter very much. On the intake stroke, there is
>essentially no side thrust at all, simply because cylinder pressue is
>relatively low. In fact the pressure is below atmospheric
>
>I hope that doesn't muddy the waters.
>
>Dave K.
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