Joe, you could figure this out! The bottom of the tire contacts the surface
so it is at zero speed at any instant. The axle is at the forward velocity
of the vehicle. The top of the tire is at twice the forward speed of the
vehicle. Air hitting the very topmost of the tire (line drawn through the
center of the contact patch and axle at the top of the tire) is going in the
opposite direction of the vehicle so it makes the speed of the interface
there at 3 times the vehicle speed. SInce the speed of sound is about 1150
fps for standard conditions then the vehicle speed has to be around 38e fps
or 261 mph. Now, th etire has a boundary layer velocity that slow down the
farther away from the tire you get, so the only point that is supersonic is
the one molecule that is attacehed to the tire. Now to make matters worse,
the air goes into turbulkence around 20 degrees from the vertical so even
that one molecule probably cannot get supersonic.
IMHO
mayf, farkling around today. Nice in Pahrump...
----- Original Message -----
From: "Joe & Lynne Lance" <jolylance@earthlink.net>
To: "John Burk" <joyseydevil@comcast.net>; <land-speed@autox.team.net>
Sent: Thursday, February 03, 2005 10:54 AM
Subject: Re: Rotation Drag
> Interesting---So if an open wheel car moves fast enough you could get a
> sonic boom from the top of the tires?
>
> Lance
>
>
> When you think of the
> > tops of Joe Laws and Fast Freddies tires going through the air at nearly
> the
> > speed of sound I would think that might add greatly to the wheels drag -
> > May-be it's the fact that the bottom of the tire has no foreward speed-
> Saw at
> > a place I've forgotten that the Cd for the frontal area of a tire is .58
.
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