On Nov 17, 2008, at 7:28 PM, Elon wrote:
Skip I am only responding to Jon's definition. He says 'patch' is the
square
inches of rubber in contact with the ground. Using that definition the
patch
area will vary with surface density or hardness. Keeping the load and
pressure the same, apply the tire to two different surfaces. In the
morning
the salt is hard, dry and cold. In the afternoon the salt is hot, soft
and
moist. Two different surface characteristics but with exactly the same
tire
load and pressure. The latter surface will have more patch area
because the
tire will imbed or sink further into the surface more than the former
condition. Even though we are talking thousandths of an inch here the
patch
area changes with the medium. The more the tire sinks in, the greater
the
rubber area in contact with the surface medium, no?
Okay Elon -- I'll go along with that. Surface might change the size
of the patch if the tire sinks in to said surface. But -- let's back
up and rule out anything other than an ideal surface, just so I can
get the most basic solution to my query. But wait -- maybe you're not
right after all. Other than the part of the tread surface that's on
an angle (not parallel to the ground) giving a different amount of
support (because now we've brought geometry into the equation (or, if
you will, a third dimension vs. just width and length) you'll still
got the same pressure in the tire and therefore the same required
amount of square inches of contact area to support the weight.
If you've got 1200 pounds on the tire and thirty pounds/sq. in.
pressure in it -- you'll have forty square inches of tire on the
ground, right? And if you want forty square inches of contact patch
and you've only got an 800-pound wheel weight -- you'll need to run
only 20 psi.
Remember -- leave heating, handling, squirm, tread pattern, surface
density -- leave 'em all out and let's get the very basic part of the
problem solved first. Maybe I'm being way too pedantic here -- but
before I get into the rest of the variables I want to be sure I know
the first step.
Jon Wennerberg
Tall guy with moustache
and a pair of 2 Club hats
_______________________________________________
Support Team.Net http://www.team.net/donate.html
Land-speed mailing list
http://autox.team.net/mailman/listinfo/land-speed
|