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Re: calculated speed

To: "Dan Dwelley" <maine2me@yahoo.com>, <spridgets@autox.team.net>
Subject: Re: calculated speed
Date: Tue, 13 Jun 2000 10:59:17 -0700charset="iso-8859-1"
References: <20000613173741.18667.qmail@web1503.mail.yahoo.com>
Good thought Dan,

but my years calibrating bicycle cyclometers suggests rather strongly that
the same tire measured in the unloaded state will give a significantly
different circumference when loaded and rolled on the ground.  Just look how
much the radius from the center of the wheel to the surface of the ground
changes as you lower a tire to the ground with the jack.  Between the
unloaded state(just touching the ground),  and the point that it is bearing
its full share of the weight, you will see a definite reduction in the
radius.
On a bicycle, the unloaded circumference will result in a significant error
compared to the rolling circumference.  Over a 200 mile bike ride, it was
several miles difference.

Regards,
Glen Byrns
'59 bugeye

----- Original Message -----
From "Dan Dwelley" <maine2me at yahoo.com>
To: "Glen Byrns" <grbyrns@ucdavis.edu>; <spridgets@autox.team.net>
Sent: Tuesday, June 13, 2000 10:37 AM
Subject: Re: calculated speed


> > 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)))
>
>



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