On Date: Wed, 26 Sep 2001 21:57:33, Eric Linnhoff
<knuckledragger@kcweb.net> said:
>Where in the rules does it state that one can not have their car running
>while in grid? What, we're not allowed to let our cars warm up now?
Nothing against running the car in grid. Nothing against warming up the
car... HOWEVER, there are some exceptions related to the rule prohibiting
the preheating of tires by means of electric heaters "or similar means".
Read on.
>Must one let the car completely cool down before enveloping their car with
>the shiny-fence thingy?
No.
>You're not "artificially" creating heat but rather
>just using the natural by-product of an internal combustion engine, heat,
to
>warm the tires.
Yes, but -- only the *residual* heat left in the vehicle as a whole after
the run because... (keep reading...)
>You're not "directing" the heat in any strange manner but
>rather just keeping it in and around the entire undercarriage of the car
>with the reflective material.
True, unless the car is running. (you're getting closer...)
>How does that differ from covering the tires
>after a run to keep the heat in them that was attained during a run? No,
I
>know _how_ it differs but explain it to me in legal, rule book lawyer-ese.
>How would those two situations differ in the eyes of our current rules?
Here's the quandary. You *know* how it differs: With the engine off, you
are merely *containing* and slowing the dissipation of *existing* heat from
the vehicle. *No* *active* *method* is being used -- you simply added an
insulating blanket. With the engine *on*, however, you are continuing to
*generate* heat, and, by putting the skirt around the entire underbody of
the car, you are changing the airflow patterns of *where* the heat goes,
encouraging it to go to the tires and other underbody components. Under
these conditions, even an electric-fan-only car will likely have the fan
running (I know these things 'cause I'm an automotive thermal management
engineer). Engine off, it's "passive". Engine on, it's *active", and thus
a "similar means" to electric tire blankets in that heat is being
*generated* for the sole purpose of warming the tires.
There's a further danger involved with this situation (running the car at
idle with the underbody skirted). There's a good deal of heat coming off
the exhaust system. It's designed to have *some* airflow over it to
prevent that heat from cooking the things above it (carpet, center
consoles, your feet, rear suspension, fuel tank, trunk mat, spare tire,
etc.) Skirting the underbody while the engine is running will prevent that
airflow and there's a very real risk of a "thermal event" if it goes on
long enough.
>Would it be illegal for someone to use a passive solar redirection panel
to
>concentrate and aim the solar radiation towards their tires thereby
warming
>them? If so, how would you define the illegality?
If you are taking an action whose sole purpose is to direct *external*
thermal energy to the tires by means of some device (in this case, the
reflector you're using to shine the sun on the shady-side tires), you're
using "similar means" to electric tire blankets.
My original plan for the tire blankets I made in John McIver and my Days
Inn hotel room in Moultrie, Georgia, in 1996, prior to the coldest National
Tour I've ever attended (I think we hit 39 degrees peak for the entire
weekend) was to get a bunch of dryer duct and make up a system that clipped
over the dash vents and directed hot air to the tires from the car's
heater. A quick re-read of the rule book convinced me that it was "similar
means" to an electric tire blanket and thus not legal, and the blankets
remained passive insulators only. John's still using them, I saw, although
he's had to add more duct tape. The highest tire temperature I heard that
weekend, by the way, was off the rear tires of Bruce Wentzel's original
Green Dot big-block BSP Corvette, and he got them up to 63 degrees. Not
163. 63. Fahrenheit.
>How about tire blankets
>made of "super solar radiation absorbing material(TM)"? Is sunlight now
>protestable too? Has placing one's warm buttocks upon a tire now become
>behavior that should make one ready to be protested?
Some folks have painted their passive tire insulators black on the outside,
presumably to absorb whatever thermal energy from the sun is around. Saw a
few of these at Nats this year. Quite frankly, under the conditions where
tire blankets are most often used, there's generally not a whole lot of
solar IR around, so I don't know how effective it might be. Would be
interesting to do a thermal study, perhaps. There are a number of people
who, while parked in grid prior to their heat, would turn the car around
the opposite way for a bit to "even" the solar heating on the tires as best
they could, but every one of those folks did NOT use blankets.
Even your arse isn't going to be warm enough to transfer effective heat
into a tire, Eric, :) so that last possibility is certainly not going to be
an issue. I saw people in grid Friday 1st heat leaning up against cars
after runs to warm their buns, not transfer Butt Heat! (TM Goeke, Bauer,
Hedley, Gill) to the car/tires.
Hope this makes a little more sense now.
Jim "Thermal Engineer to the Stars, currently the Pentastar" Crider
autojim@att.net
jac73@dcx.com (work)
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