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From: John De Armond
Subject: Re: Dodge (Cummins) v/s Ford (Powerstroke)
Date: Fri, 24 Mar 2000 02:10:25 EST
Newsgroups: rec.outdoors.rv-travel

Chuck wrote:

> >This uncleof yours is blowing smoke big time, since one of the
> >important differences between vee and inline engines is that the vee
> >engine has a SHORTER crankshaft.  Your credibility on the other issues
> >kinda went down the toilet with that booboo.   Try getting some other
> >uncle to give you the straight story.
> Maybe I mis-stated the point I was trying to get across with a very
> very, bad example.   I remember him talking about an inherent weakness
> of the crankshaft in any V configured high-torque diesel engine as
> compared to an Inline.  He talked about actual crank breakage.  They
> service Mack (of course), Cummins, International and one of the
> Japanse small diesel delivery truck line.  I felt sure he talked about
> length but you are right, unless there is something drastically
> different in the crankshaft for a diesel engine v/s a gas engine (and
> how could there be?)

Chuck, actually you and your uncle are absolutely correct.  I can't
imagine anyone operating at any higher level than Sill to even argue
other side.  The V engine is a very nice design for a light weight,
high speed, moderate BMEP engine.  But it has several fundamental
weaknesses that preclude its optimal use for high torque, high BMEP
engines.  First is the issue of there being two rods on one crank
pin between each pair of main bearings.  Not only is this inherently
weaker than the inline design with mains between each cylinder
(except for certain British engines :-), it also introduces a strong
rocking couple between the ends of the crank pin.  To get the
cylinders as close as possible together, the space for the crank
journal is limited, resulting in a relatively thin throw web.

This is all pretty much engine engineering 101 stuff.  The tradeoff
in weight and size vs strength is well known and not an issue of
debate.  Where weight and size aren't primary issues, the inline is
a natural.  Stiffer block, stronger crank, bearings for each
cylinder, ability to achieve perfect primary balance are all
attributes of the inline.  The V works well for the applications it
is designed for and the inline works well for the applications IT is
designed for.  No real issue here.

I thought your post was quite understandable and on-point.  No need
to apologize, particularly in this instance.


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