Piston Weights

Jake Meyer meyerjme at gmail.com
Thu Mar 13 22:45:12 PDT 2008


Awesome.  Thanks for the run down :)

On 3/13/08, zoran <zv30 at sbcglobal.net> wrote:
>
> actually I have been building and fixing motors/bikes for at least 30
> years.I just did not do it for other people as much as now.
> and 08 is going to be my 20th year racing.
> still about 40 years behind Earnie :)
>
>
> Zoran Vujasinovic
> Twin Works Factory
> 775-786-4881
> www.twfracing.com
> ----- Original Message -----
> From: "Ernest Montague" <afm199 at earthlink.net>
> To: "Suzuki SV650 Mailing List" <sv650 at micapeak.com>
> Sent: Thursday, March 13, 2008 7:26 PM
> Subject: Re: Piston Weights
>
>
> > Actually when I came to the list Zoran  had the most knowledge, and
> Randy
> > had a lot of good ideas. I've picked up a bit over the years, mostly
> > because I do most of my own work and crash too much (LOL).  I think KC
> > showed up a year or two later.
> >
> >  KC has been building motors forever.  I remember him from twenty years
> > ago, when I was a kid for forty. Back before SVs. I was picking his
> brains
> > then, I doubt he remembers.
> >
> >
> >
> > On Mar 13, 2008, at 6:24 PM, Randy Grein wrote:
> >
> >> There are a few others, while not builders or engineers have
> significant
> >> experience/knowledge regarding racing. Ernie generally knows what he's
> >> talking about. Z and KC are major builders and racers (former); you
> guys
> >> have what - about 40 years experience between you? I (usually) know
> what
> >> I'm talking about although there are days... (grin). I'm pretty good
> with
> >> the physics of racing and condensing explanations into layman terms but
> >> leave the actual engine building to guys with the specialized knowledge
> >> to do so. The racers here generally have years of experience and do
> >> (most) of their own work.
> >>
> >> The knowledge/BS ratio is pretty high here, esp. compared to some other
> >> lists I've read. A pure BS answer lasts about 30 seconds and I can't
> >> recall an actual fight about anything. Feel free to chime in - a lot of
> >> tech discussions are like this one, very collaborative.
> >>
> >> Randy Grein, WMRRA #41
> >> Micapeak SV list admin
> >>
> >> On Mar 13, 2008, at 3:54 PM, Ernest Montague wrote:
> >>
> >>> You are getting decades of experience from a couple of the top engine
> >>> builders around, neither of whom has a degree in engineering. However
> >>> their bikes win races. Take that for what it is worth. I know there
> are
> >>> a couple engineers on the list. My GF is an engineer.  (PE) Her job is
> >>> to run a company that monitors the growth of invasive species in the
> SF
> >>> bay.
> >>>
> >>>
> >>> On Mar 13, 2008, at 3:31 PM, Jake Meyer wrote:
> >>>
> >>>> I know I'm a n00b here, but I have to ask - how many people on this
> >>>> e-mail
> >>>> list are engineers?  mechanics?  I'm just wondering how many years of
> >>>> design/build/repair/modify experience is sitting in my inbox on any
> >>>> given
> >>>> day...  I'm a mechanical engineer with only about 7 years experience
> >>>> working
> >>>> on cars.  Zero experience on bikes :) - so thanks to everyone for
> >>>> sharing
> >>>> your knowledge and experience.
> >>>>
> >>>> Jake
> >>>>
> >>>>
> >>>> On 3/13/08, KC Gager <kc at brgracing.com> wrote:
> >>>>>
> >>>>> Spot on Randy
> >>>>> The problem with piston weight is the surface area that the rod has
> on
> >>>>> the
> >>>>> crank. It is design for X weight and the oil film will hold X
> weight.
> >>>>> If
> >>>>> you
> >>>>> make x heavy old film goes away and boom.
> >>>>>
> >>>>> KC Gager
> >>>>> BRG Racing Products
> >>>>> "We Have Sickness For Quickness"
> >>>>> KC at brgracing.com
> >>>>> http://www.brgracing.com
> >>>>> (925)672-5789
> >>>>>
> >>>>>
> >>>>> -----Original Message-----
> >>>>> From: Randy Grein [mailto:randygrein at comcast.net]
> >>>>> Sent: Thursday, March 13, 2008 6:19 AM
> >>>>> To: Suzuki SV650 Mailing List
> >>>>> Subject: Re: Piston Weights
> >>>>>
> >>>>> No. Neither reciprocating nor rotating mass affect torque. An
> increase
> >>>>> in rotating mass evens out power output making it easier to feather
> >>>>> the throttle (like spinning coming out of  a corner), and does
> provide
> >>>>> a slight increase in acceleration (measured torque and power on a
> >>>>> Dynojet dyno), but the few grams we're talking about here between
> >>>>> pistons isn't enough to notice. Piston weight does affect the
> optimal
> >>>>> crank balance; go light or heavy enough and you'd increase
> vibration)
> >>>>> but the primary impact is on crank/rod stress. Big heavy pistons
> break
> >>>>> cranks at high rpms.
> >>>>>
> >>>>> Your drive line deformation argument is interesting, but except for
> >>>>> the clutch basket springs and sprocket cushions there isn't any to
> >>>>> speak of at this level. Parts that deformed enough to materially
> >>>>> impact power delivery, even instantaneous power delivery would be
> >>>>> deforming significantly and break in short order. Yes, there is some
> >>>>> deformation, which is why we don't make cranks out of aluminum, but
> >>>>> for the effect you're thinking of to be noticeable deformation would
> >>>>> have to be plastic and on the order of 10-20 degrees of crank
> rotation
> >>>>> every half  engine rotation.
> >>>>>
> >>>>> Randy Grein, WMRRA #41
> >>>>>
> >>>>> On Mar 13, 2008, at 5:35 AM, Ilya A. Kriveshko wrote:
> >>>>>
> >>>>>> Steve Robertson wrote:
> >>>>>>> So do those boat anchor Wiseco pistons make good torque :-)
> >>>>>>
> >>>>>> I understand it's a joke. But pretending for a second you were
> >>>>>> serious,
> >>>>>> let me ask the gear heads on the list: would a heavier
> >>>>>> *reciprocating*
> >>>>>> mass affect torque figures? And how?
> >>>>>>
> >>>>>> My own gut feel is that unlike heavier rotating mass, heavier
> >>>>>> reciprocating mass would actually reduce output torque.
> >>>>>>
> >>>>>> Heavier *rotating* mass would increase the mean torque over the
> >>>>>> cycle,
> >>>>>> by borrowing from the sharp and short power peak and spreading it
> >>>>>> around
> >>>>>> the ~3x wider valley. Normally, the sharper the power peak (i.e.
> the
> >>>>>> quicker it changes), the more of its energy gets dissipated via
> >>>>>> material
> >>>>>> deformation in the drive line. Lowering and widening the peak
> allows
> >>>>>> the
> >>>>>> various stresses to rise and fall at a slower rate, thereby wasting
> >>>>>> less
> >>>>>> energy on component deformation, and delivering more of it to the
> >>>>>> output
> >>>>>> shaft.
> >>>>>>
> >>>>>> However, it seems that heavier *reciprocating* mass would not have
> >>>>>> the
> >>>>>> same full-cycle peak spreading effect. It would rather amplify the
> >>>>>> harmonic of positive and negative inertial torque effects that is
> >>>>>> overlaying the combustion torque curve. If anything, that would
> >>>>>> produce
> >>>>>> more sharp combined torque rises and falls, creating peaks and
> >>>>>> valleys,
> >>>>>> producing more stress, sapping energy and wearing components. The
> >>>>>> torque
> >>>>>> measured on the output shaft would probably fall.
> >>>>>>
> >>>>>> Anyhow, that's how I explain it to myself. Barring confusing
> >>>>>> terminology
> >>>>>> and lacking clarity, do I have the right picture in mind?
> >>>>>> --
> >>>>>> Ilya
> >>>>>>
> >>>>>
> >>>>>
> >>>>
> >>>
> >>
> >
>
>


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