>From my limited experience with Aircraft engines and reading some books on
overhauling various engines, I think we can say that there are various
levels of "balancing" or "Matching" of internal components.
The most basic level and easiest to do would be the simple matching of parts
that I described. weigh all of the parts and mix them accordingly to achieve
the closest average weight. This will produce some improvement in vibration
levels. You might be surprised at how much different two pistons can weigh.
The next level would be the careful weighing of all like parts and bringing
their weights to the same level.
the next and top level would be the same as above, but paying careful
attention to where the extra mass is on each piece and modifying it to not
only weigh the same as the rest, but to have the same balance points. This
would insure the rotational masses would be the same. In a multi cylinder
oppose engine this would be important. I'm not sure it would buy you
anything in a inline four.
If your going to this level you'd need to have the crank, flywheel, and
harmonic damper all done as one unit. You could even go as far as the cam
and cam gear. While your at it, you'd want to have the head matched and
balanced. Which would entail flow matching each intake port to the rest and
exhaust port to the rest, etc etc........
So to answer Brad's original question. Seeing that he has a three beam
scale, I'd do the easiest level. weigh and match the parts to get close.
then take the flywheel, crank and harmonic damper in and have them spun
balanced.
Completely off topic. Some California police departments consider a triple
beam "Drug paraphernalia" and will treat it as such.
-----Original Message-----
From Bryan Vandiver [mailto:bryan.vandiver at sun.com]
Sent: Wednesday, January 17, 2001 10:54 AM
To: Elliott Patrick
Cc: 'Frank Clarici'; Brad Fornal; Spridgets List
Subject: Re: Piston Balancing
We actually did a thread on this several months back. I described to a
certain extent how the machinist balanced my pistons and rods, and also
did a 'dynamic' balance of my crank/harmonic-balancer/flywheel. There is
more to balancing the pistons and rods, than just making sure they all
weigh the same. When they weighed and balanced the rods, they used a
'knife edge' to support the small end, and placed the big end on a
scale. The rod was held at a specific angle when this was done. I can't
remember if it was exactly horizontal, or if it was at some specific
angle (i.e. 20 degrees) from horizontal.
Balancing does make the engine run smoother, and less vibration means
less wear and tear on the crank, and bearings, giving you better engine
life.
Bryan Vandiver (59-bugeye/1275)
San Jose, CA
"Elliott, Patrick" wrote:
>
> Balancing in this case would mean ensuring that each piston con rod pair
> weighed close to the same.
> you weigh all the individual pieces then put the heaviest piston with the
> lightest connecting rod. or whatever combination would result in the
closest
> matching of weights. depending on how anal you what to be, you could even
> shave off the casting marks, polish, and shot peen all of the pieces
before
> hand. Then fine tune the weights by dimple drilling out extra mass.
>
> Would you notice a difference? maybe. couldn't hurt if you've got the time
> and scales to do it.
>
> -----Original Message-----
> From: Frank Clarici [mailto:spritenut@Exit109.com]
> Sent: Tuesday, January 16, 2001 5:49 PM
> To: Brad Fornal
> Cc: Spridgets List
> Subject: Re: Piston Balancing
>
> Brad Fornal wrote:
>
> > I have a set of triple beams and wondering if anything would be gained
> > by balancing the pistons and rods.
>
> Brad, I may be way off here, but the 1275 has offset con rods,
> I don't think you can balance them. Well I'm sure they can be balanced
> but being offset would require about 8oz of weight added to the other
> side of the rod.
>
> Now having the crank/flywheel balanced is something that is worth the
> cost.
>
> Stick me back in your address book.
> --
>
> Frank Clarici
> Toms River, NJ
> Too Many Sprites Again
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