Re: [Phys-l] Another tire question

["LaMontagne, Bob" <RLAMONT@providence.edu>]

Is this another case of talking past each other? I assume that what we
are calling the "bead" is simply the collar that contacts the rim of the
tire. If that assumption is correct, then the collar "hangs" from the
sidewall (which I assume is the visible side portion of the tire when it
is on the wheel.) I think the hangup here is trying to envision how a
"bead" which cannot physically grab the wheel can exert an upward force.
The sidewall certainly can pull the collar (bead?) up - and the collar
(bead) really becomes part of the rim after mounting simply because of
tension pulling it against the rim since it is acting like a taut
elastic band. The bead acts like a sling but with a radially inward
tension acting on its entire circumference. The upper sidewall pulls up
on this sling.

Bob at PC

> -----Original Message-----
> From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> bounces@carnot.physics.buffalo.edu] On Behalf Of Jeffrey Schnick
> Sent: Friday, November 09, 2007 11:49 AM
> To: Forum for Physics Educators
> Subject: Re: [Phys-l] Another tire question
>
> > -----Original Message-----
> > From: phys-l-bounces@carnot.physics.buffalo.edu [mailto:phys-l-
> > bounces@carnot.physics.buffalo.edu] On Behalf Of Rick Tarara
> > Sent: Friday, November 09, 2007 10:35 AM
> > To: Forum for Physics Educators
> > Subject: Re: [Phys-l] Another tire question
> >
> >
> > ----- Original Message -----
> > From: "Jeffrey Schnick" <JSchnick@Anselm.Edu>
> >
> > > > The axle "hangs" from the top rim via the top spokes.  The rim
> "hangs"
> > > > from the top sidewall of the tire.
> > >
> > > No.  The bead hangs from the top sidewall.  The rim is supported
> from
> > > below by the bead.
> >
> > Do you mean the rim/wheel is pushed up from below by the bead,
>
> Yes, as in my previous message in this thread:
<https://carnot.physics.buffalo.edu/archives/2007/11_2007/msg00071.html>
> > or that a
> > rim
> > on the top of the wheel that traps the bead is pushed up by the
bead.
> The
> > latter is, IMO, the same as hanging from the bead which is hanging
> from
> > the
> > sidewall.
>
> The bead is not trapped in the sense that, if it weren't for the
tension
> in the bead, you could pull any piece of it radially outward, away
from
> the center of the circle formed by the bead.
> The bead's position is constrained by the hub in the following sense:
> Viewing a rear wheel a position behind the car, directly behind the
rear
> wheel you are looking at: The rim is shaped so that the right bead
can't
> slide rightward off the rim, and the rim is shaped so that the left
bead
> can't slide leftward off the rim.
>
> Look at the bead seat in the diagram
> <http://www.alloywheelsindia.com/images/crosssection.jpg>
> referenced by John Denker in the message (in this thread) at
<https://carnot.physics.buffalo.edu/archives/2007/11_2007/msg00034.html>
> > Seems to me that an answer to this is to carefully look at a car
> wheel--
> > does
> > anyone have one available or can you get down to a HS auto shop?  IS
> the
> > bead of a mounted tire trapped or not (I'm thinking not).  If not
> trapped,
> > then I can't see how the wheel can hang from the bead.  If it is
> trapped,
> > that is certainly a possibility.
> >
> >
> > Rick
> >
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