Bored, so I nerded out on rad/stroke ratio

[amalventano at sc.rr.com (Allyn)]

ok, i get how the piston accel is lower with longer throws, but i always
thought the main limit for the bottom end was the mean piston speed. issue
being getting enough oil to keep the rings cool and the skirt lubed.
Al

----- Original Message ----- 
From: "Ron Pieper" <rapieper@yahoo.com>
To: <scirocco-l@scirocco.org>
Sent: Saturday, January 31, 2004 12:25 PM
Subject: Bored, so I nerded out on rad/stroke ratio


> Momma wanted to watch her Thursday night TV, and the kids were in bed, and
it was too cold to work
> in the garage, so with nothing else to do, I figured I'd see what the the
scoop was behind varying
> the con rod/stroke ratio.
>
> Gotta DIY, being me, so I did some trig in Excel and a little (very crude)
derivation, I came up
> with this:
>
> http://scirocco.dhs.org/cheapassron/misc/rodratio.jpg
>
> No units (AFA ft/s/s, etc.) but I do believe it works as a visual aid.
The center of the graph is
> TDC.  Obviously something is wrong with the Y axis offset, but I think the
shape is right.
>
> This is not new news, but from what I see, it tells me that longer
rod/stroke ratios lead to
> overall lower piston acceleration rates (meaning less stress and higher
revability?) and later
> peak accleration (meaning compensations in cam (less overlap required?),
intake, and exhaust
> design, but what exactly I don't know).  Anyhow, some of you MatLab gurus
may want to pick up on
> this and discuss what positive impacts one could make on a NA engine.  Oh,
and fix my spreadsheet
> (verrrry crude) http://scirocco.dhs.org/cheapassron/misc/piston_speed.xls
>
> Now, back to your normally scheduled discussions...
>
> =====
> Cheapass Ron
> '81 Scirocco S - "Victor Jr."  7SM
> (2.0L 16V, GL 4-speed w/ Quaife installed, Megasquirt coming...)
>
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