Sort of like static and dynamic on a tire?
John B
----- Original Message -----
From: "Dave Dahlgren" <ddahlgren@snet.net>
To: <ardunbill@webtv.net>; <land-speed@autox.team.net>; <bigsid@webtv.net>;
"marco" <bk185@lafn.org>; <bjgayle@aol.com>; <ddferguson@msn.com>;
<LITNMAN@aol.com>; <gillette@gateway.net>; <clemtebow@aol.com>
Sent: Saturday, January 20, 2001 1:06 PM
Subject: Re: V-8 Engine Balancing
> I can't believe that i forgot one of the most important
> aspects of the balance job. There are 2 types of inbalance,
> force and couple. Force is the balance of a part that is
> easiest described as in a plane 90 degrees to the center of
> the crankshaft. This is also the balance that would be
> derived if the crank was static balanced. There is also
> couple. Most easily imagined for me at least as the in
> balance that is 90 degrees to the ends of the crank. For
> example you could have a crank that is 10 grams light at one
> end and 10 grams heavy at the other. In couple this would be
> a 20 gram error in force the error is 0. Yes you have to get
> them both right.
> Dave
>
> Dave Dahlgren wrote:
> >
> > Balancing can and will take tons of stress out not hundreds
> > of pounds.. And the lighter the parts the less the stress.
> > If I was racing an engine with 3 mains i would own the
> > lightest stuff i could find..
> > 1 gram is common place work now and has been for 20 years if
> > the shop is any good at all.
> > The trick with the 2 ends and error is to balance 1 end in
> > the fixture usually the big end if memory serves me right..
> > get them all the same the do a total weight to get the small
> > end.. swapping parts around ought to be a last resort for
> > me.. the best way to do it is pair up all the big ends for a
> > 2 big end weight that is the same. then use the small end
> > weight difference to mix and match the different pistons..
> > then you can come up with a correct bob weight.
> > On the subject of bob weight it does not have to be a 50% of
> > reciprocating weight deal and depending on your rpm you may
> > want to go to 51 or 52%.. the real beauty of a 51% job is
> > later on if you have some new bob weight and it falls within
> > 50% to 52% you are good to go with no rebalance on the
> > crank.
> > The real thing to remember is that the balance job is only
> > valid over an rpm range not from 0 to 9000 rpm. The higher
> > the RPM the more you have to look at more than 50% recip..
> > many slower turning engines are balanced at less than 50%
> > BTW.. On some of the small stuff i have worked on that
> > really turns up (10 to 13k rpm) i have used 54%.. I spent a
> > lot of time with the engineers and field guys at Stewart
> > Warner years ago on this very subject for Winston Cup
> > stuff.. if you are mathematically inclined there is a bunch
> > of good stuff that is written on this subject. I would
> > suggest Stewart Warner a good place to start for a suggested
> > reading list.
> > Hope this helps a bit
> > Dave Dahlgren
> >
> > ardunbill@webtv.net wrote:
> > >
> > > Hi Folks, recently delved into this subject, one I've always found of
> > > interest, because I had to consider it for my 290 Ardun. After
talking
> > > to various experts and reviewing the literature, I realized it is
> > > necessary, at least this time.
> > >
> ><snip>
> > >
> > > The above is merely what this amateur has been able to learn about V-8
> > > balancing up to this point, so I hope the real experts and veterans on
> > > this List will point out any errors they see. Cheers from Ardun Bill
in
> > > the Great Dismal Swamp, Chesapeake, VA
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