BRAVO!!! Applause......
New meaning to the term Colonel Mustard in the fast food store!
May I forward this to another car interest list?
EAP
----- Original Message -----
From: "pensioner" <al_knoll@PACBELL.NET>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Wednesday, January 31, 2001 12:18 PM
Subject: Tire rollout, per jbrandt@hpl

> Are we tired yet?
>
> Some many years ago Klaus at Palo Alto Speedometer gave me the wizard's
> secret to getting that Tripmaster DFO.
>
> Grasshopper, sez he, the lowly tripmaster knows not of tire height,  even
> more it knows not of tire at all.  It only knows axle rotations.
>
> So...per the jbrandt of 356/torsion bar and bicycle fame.   Use mustard.
>
> Gitchaself on over to yer fave fast food store and snap up two or three
> packages of good ol' bright yellow mustard.
>
> Find a straight place in a parking lot or quiet street
>
> Aim the vehicle in question in a straight line.
>
> Place a thick line of mustard in front of the wheel to be measured.
>
> Drive forward slowly through the mustard.
>
> When you think you've gone twenty feet or so go another two feet.
>
> Set the parking brake.
>
> Inspect your tracks for THREE mustard marks.  The original, the first
> revolution and the second revolution.
>
> If only two marks check to see if you have completed two wheel rotations.
> If not get back in, release parking brake and move forward until you have
> three mustards.
>
> Using a laser interferometer or other measuring device ( A 30' Craftsman
> Steel tape is my battery and pollution free portable measuring tool of
> choice for this application) measure the first edge to first edge between
#1
> MM and #2 MM (Mustard Mark).  One percent of thutty feet is like a quarter
> inch so get it to a quarter inch.  Measure twice.  Cut nonce.
>
> Now convert the measurement to your units of choice, nanometers, furlongs,
> light years.  I tend to use feet to tenths.
>
> Now you know the "rollout" for two revolutions of the wheel.
>
> With this secret knowledge written in the back of the owners manual with
> date and tire size and inflation pressure and ambient or tire temperature
> you can venture into the world of adjusting your gearing to suit your
fancy.
>
> Call this constant 2RO1.
>
> Derek's  fine work can calculate wheel rotations as a basis of rpm and
> gearing.  Knowing your RO1 (half of the 2RO1, calculated)  you can predict
> revolutions per mile, revolutions per minute versus an approximate miles
per
> hour AND you can use common math to get an actual wheel diameter or radius
> for your particular wheelset (sorry JB).
>
> In metrics we learned that any quantity contains a linear error of
> measurement, call it "error"  If you multiply the quantity by a constant
> greater than one you also increase the absolute error.  If you divide the
> quantity by a constant greater than one you reduce the absolute error,
hence
> three mustards..  Four is impractical as consumer grade mustard only marks
> distinctly thrice.   You DID mark the REAR WHEEL, right?  Else you are
> subject to recursive and multiple mustards.  To do the front wheel you use
> reverse gear, natch?
>
> You can use a measured highway marker set or a gps or other method to
> achieve much the same accuracy at greater bother.  One percent is as good
an
> engineering estimate as is needed for these calculations as they are range
> limited.  EG:  one does not have a continuous set of solutions as gear
sets
> are integral devices.  32:11 gives one ratio solution 33:11 gives a second
> and 33:10 gives one in the middle.  Machinists even good machinists balk
at
> cutting a gear with ten and a half teeth.
>
> now back to your regularly scheduled programming.
>
> pensioner