Just a thought on rolling resistance .. The rolling resistance of tires go
down on NASCAR cars greatly above 90mph do to the centrifugal forces on the
tires.
Doug Mallory
-----Original Message-----
From: DrMayf@aol.com <DrMayf@aol.com>
To: tigers@autox.team.net <tigers@autox.team.net>
Date: Saturday, October 10, 1998 9:28 PM
Subject: Bonneville HP (was Rods and Rants and other stuff)
>Drat! One of the comments is going to cause me to turnup the turbo boost.
The
>rolling resistance is higher than I had been using. Yes, I made a MISTAKE!
I
>was using a formula that dis not include the speed regime under
consideration.
>I believe the correct formula is the right one to use. It comes from the
>"Fundamental of Vehicle Dynamics" by Tom Gillespie, 1992, page 117.
>
> Fr = Fo + 3.24 * Fs * (V/100)^2.5
> where Fo and Fs are coefficients found from a table of tire pressure.
>
>Bonneville tires are run at 45 psig or higher to reduce rolling friction
but
>thats about as high as the graph for the coefficients go. In this case
>
> Fo = 0.008, Fs = 0.002, V = speed in mph
>
>and of course speed = 260 miles/hour
>
> Fr = 0.008 + 3.24 * 0.002 * (260/100)^2.5 = 0.0786
>
>Loss in lbf = Fr * W
> W = vehicle weight = apprx 2000lbs
>
>So Loss = 0.0786 * 2000 = 157.3 lbf
>
>Hp loss = Loss * V / 550 = 157.3 * 381.3 /550 = 109.2 hp. (this V is fps,
not
>mph)
>
>Ok, crap. Well in for a penny, in for a pound. There are mechanical systems
>losses also. My famous text indicates about 10 percent mechanical losses
which
>includes the tranny and rear end. Since I am using a lockup converter it
may
>not have an effect.
>
>Adding to what I had already calculated as needed horsepower, 481.5 at
>Bonneville altitude in August, I have
>
>Flywheel hp = 481.5 + 109.2 + 48.1 = 638.8 hp
>
>Will I ever get this? Who knows! Improvements are an ice cooled Intercooler
to
>drop the temperature of the engine air charge to ambient or below,
increasing
>density and adding power. Also, I still have another 50 percent boost from
>these turbos according to the compressor maps for the Garrett T03s I am
>using.
>
>Now, I know that at least one of you is going to challenge something else,
but
>please let's make it something new. And remember, that the goal was and is
>still to have the fastest Sunbeam on the planet. If that just barely beats
he
>old Sunbeam streamliner's speed of 203.792, I'll be happy for a while. And
>when I drag race it, I want it to be the quickest on the planet. Please
note
>also, that this is not advertised as a Tiger or Alger or Alpine, but simply
as
>Sunbeam. I again challenge the mechanically talented of you to bring your
cars
>to Bonneville standards and meet me there someday. Nothing like a time slip
to
>make your point.
>
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