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Re: calculated speed

To: Toby Atwater <tob.sprite.landcruiser@home.com>
Subject: Re: calculated speed
Date: Tue, 13 Jun 2000 19:53:31 -0700
Cc: Spridgets list <spridgets@autox.team.net>
Organization: WFO Racing
References: <Springmail.105.960923152.0.24454200@www.springmail.com> <00dc01bfd59b$fcc6d700$0200a8c0@homr>
Toby,

Happy belated... or early... birthday (young fellow)!

Toby Atwater wrote:

> I'm technically a child of the eighties (Jan 1980 DOB)... line is from
> "Stripes" Mr Psyco needs to ligten up or Ill Kill you!.
>
> Toby
>
> > Ah....  A child of the eighties.  I bet less than 1 in 1000 kids younger
> than 18 can identify that line......  In ten years,   1 in 1000 younger than
> 18 will be able to identify the _biggest_ actor in the movie.  Folks,  I'm
> getting old.....
> >
> > Michael
> > '78 Midget (I'm sorry,  did you want me to move on my own power?)
> >
> >
> > Dan Dwelley <maine2me@yahoo.com> wrote:
> > > "Lighten up Francis!" Sounds like someone needs a hug!
> > :o))
> >
> > I was just being Facetious!
> >
> > Damn!
> >
> > Dan Dwelley
> >
> > --- John Holliday  wrote:
> > > If we are going to continue this anal discussion,
> > > the
> > > rolling circumference of the tire with the car's
> > > weight applied is different than the circumference
> > > measured on your spare tire off of the car.
> > >
> > > Better still just top end your car's speed thru your
> > > local community's speed trap. Email us a copy of the
> > > citation and we will all know who's is fastest.
> > >
> > > John Holliday
> > >
> > >
> > > --- Dan Dwelley  wrote:
> > > > > Mark a spot on one rear tire and roll the car so
> > > > the
> > > > > mark touches the
> > > > > pavement. Mark the pavement at this point.  Roll
> > > > the
> > > > > car forward with you in
> > > > > it (for highest accuracy) until the mark on the
> > > > tire
> > > > > is again on the ground.
> > > > > Mark this spot and measure between them.  This
> > > is
> > > > > the distance the car moves
> > > > > forward for each rotation of the axle, call it
> > > > "C".
> > > > >
> > > >
> > > > "C" for Circumference? I've got a better
> > > idea...just
> > > > measure the circumference of your spare tire (if
> > > > it's
> > > > the same size as you have on your car). I bet
> > > you'll
> > > > get the same measurement with less effort! :o)
> > > >
> > > > Dan Dwelley
> > > > no wiz but I can determine the circumference of a
> > > > circle and apply it to linear measurement. :o)))
> > > >
> > > >
> > > > --- Glen Byrns  wrote:
> > > > > Here's how I figured my theoretical speed at
> > > > various
> > > > > rpm's:
> > > > >
> > > > > Mark a spot on one rear tire and roll the car so
> > > > the
> > > > > mark touches the
> > > > > pavement. Mark the pavement at this point.  Roll
> > > > the
> > > > > car forward with you in
> > > > > it (for highest accuracy) until the mark on the
> > > > tire
> > > > > is again on the ground.
> > > > > Mark this spot and measure between them.  This
> > > is
> > > > > the distance the car moves
> > > > > forward for each rotation of the axle, call it
> > > > "C".
> > > > > In my case, C=69 5/8" =
> > > > > 69.625".
> > > > >
> > > > > With a 4.2 rear end, the drive shaft will turn
> > > 4.2
> > > > > times to turn the rear
> > > > > axle one revolution.  Assuming a fourth gear
> > > ratio
> > > > > of 1:1, then at 6K rpm,
> > > > > 6000/4.2 = turns of rear tire per minute =
> > > > 1428.72.
> > > > > Multiply by 60 to get
> > > > > turns per hour, = 60 x 1428.720 = 85732.2
> > > > > This number times the number of inches forward
> > > for
> > > > > each turn you figured out
> > > > > earlier(C)tells you how many inches forward for
> > > > each
> > > > > hour at 6k rpm in
> > > > > fourth. Divide by the number of inches in a
> > > > > mile(63360) and you should get
> > > > > miles per hour.
> > > > >
> > > > > {(rpm/rear end ratio)x 60 x C }/ 63360
> > > > >
> > > > > So for a 4.2 rear end, 69.625 inches per turn of
> > > > > tire, fourth gear:
> > > > > (6000/4.2) x 60 x 69.625 / 63360 = 94.18 mph,
> > > at
> > > > 5k
> > > > > rpm = 78.49mph
> > > > >
> > > > >
> > > > > I'm sure someone with a better memory of math
> > > will
> > > > > correct me, but luckily I
> > > > > play with DNA for a living and don't do gobs of
> > > > > math.
> > > > >
> > > > >
> > > > >
> > > > > > I havn't seen anybody talk about tire size
> > > which
> > > > > can have a very difinite
> > > > > >effect on speedo error and correct top speed.
> > > > Look
> > > > > at any tire chart and
> > > > > >you will see a big difference in tire
> > > > circumference
> > > > > with the tires sizes
> > > > > >very close together if not the same size.
> > > Don't
> > > > > forget to take this into
> > > > > >consideration.  Does anyone one out there have
> > > > the
> > > > > formula for determining
> > > > > >top speed using tire circumference, axel
> > > ratios,
> > > > > and rpm's?
> > > > > >
> > > > > >
> > > > > >BOB
> > > > > >65 Midget vintage racer
> > > > >
> > > >
> > >
> > >________________________________________________________________________
> > > > > >
> > > > > >
> > > > > Regards,
> > > > > Glen Byrns
> > > > > '59 Bugeye
> > > > >
> > > >
> > > >
> > > > =====
> > > > Dan Dwelley
> > > > 77 Midget
> > > > Alexandria, Va.
> > > >
> > > > __________________________________________________
> > > > Yahoo! Photos -- now, 100 FREE prints!
> > > > http://photos.yahoo.com
> > >
> > >
> > > __________________________________________________
> > > Do You Yahoo!?
> > > Yahoo! Photos -- now, 100 FREE prints!
> > > http://photos.yahoo.com
> >
> >
> > =====
> > Dan Dwelley
> > 77 Midget
> > Alexandria, Va.
> >
> > __________________________________________________
> > Yahoo! Photos -- now, 100 FREE prints!
> > http://photos.yahoo.com
> >


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