Carl, Just considering track and overall height is simple,
but I fear it might be just a little too simple. Overall
height alone provides a poor estimate of CG height. Adding
ground clearance to the equation greatly improves the accuracy.
As we all know intuitively, a stock Ford Expedition on race
rubber is a great candidate for a flip, but one that has been
lowered to the max is probably pretty rollover-safe. And ground
clearance - perhaps at differential or oilpan - is something that
could be measured at tech on a questionable vehicle.
/Bill
------ original message ------------
Date: Fri, 20 Oct 2000 06:59:13 -0700
From: Carl Merritt <cmerritt@ati.com>
Subject: RE: Vehicle eligibility...
Ah, perfect, thanks Kevin:
Vehicle Track Height
Samurai 51.4 65.6
Wrangler 58.0 70.6
Sidekick 55.x 64.3
Previa 61.4 68.7
Camaro 60.6 51.8
Toy Van 56.7/54.5 70.3
So what if there was just a simple rule that a vehicle must be have a track
at least as wide as it is tall? Even the 2000 Focus will pass that test,
with a track of 58.5 and height of 56.3.
- -Carl
> ----------
> From: Kevin Stevens[SMTP:Kevin_Stevens@Bigfoot.com]
> Reply To: Kevin_Stevens@Bigfoot.com
> Sent: Thursday, October 19, 2000 11:19 PM
> To: Carl Merritt
> Cc: ba-autox@autox.team.net
> Subject: RE: Vehicle eligibility...
>
> Google - "Toyota Previa wheelbase track".
>
> KeS
>
> > -----Original Message-----
> > From: owner-ba-autox@autox.team.net
> > [mailto:owner-ba-autox@autox.team.net]On Behalf Of Carl Merritt
> > Sent: Thursday, October 19, 2000 21:58
> > To: 'Derek Butts'; 'kevin_stevens@hotmail.com'
> > Cc: ba-autox@autox.team.net
> > Subject: RE: Vehicle eligibility...
> >
> >
> > Sadly I can't find any measurement data on the old Toyota van, which
> also
> > had a common propensity to blow up and/or catch on fire, but that's
> another
> > story...
> >
> > Hey Kevin! Where did you get those track & height numbers on all those
> > vehicles so fast?
> >
> > -Carl
> >
> >
> > > ----------
> > > From: Derek Butts[SMTP:pnc1@earthlink.net]
> > > Sent: Thursday, October 19, 2000 4:07 PM
> > > To: Bill Hamburgen 650-617-3329 FAX -3374
> > > Cc: ba-autox@autox.team.net
> > > Subject: Re: Vehicle eligibility...
> > >
> > > In fairness to this discussion the Toyota Van I drove had 175,000
> miles on
> > > it
> > > with the original shocks and crappy tires. I think it was a 1989 with
> the
> > > narrower track and higher center of gravity. The Previa is a later
> model
> > > Toyota van with a wider track and wheelbase.
> > >
> > > Sorry, my mistake - the Previa does look like a turtle, though : )
> > > -Derek
> > >
> > > Maybe we should institute a policy that the Safety Steward test drives
> the
> > > proposed vehicle at speed and if it rolls they simply hand back the
> keys
> > > to the
> > > owner and say "this vehicle is not acceptable for Solo II" : )
> > >
> > > Bill Hamburgen 650-617-3329 FAX -3374 wrote:
> > >
> > > > I'd been holding off weighing in on this, but I can't any longer.
> > > > Derek Butts said:
> > > >
> > > > > I have driven this van before. We used to have one as a parts
> van.
> > > > > If autocrossed it will end up like an upside down turtle....
> > > >
> > > > I have both autocrossed my Previa and been up on two wheels in my
> GTI.
> > > >
> > > > My Previa is an Altrak, with a rear sway bar, good shocks, and
> slightly
> > > > lower than stock due to low profile tires (215/60-15). It handles
> > > better
> > > > than a lot of sedans. I autocrossed it once at an SFR event (at
> Alameda
> > > > NAS about 4 years ago) and my time put me in the top 80% of the
> entire
> > > > field. Beat a Porsche, a Vette, and a Tiger among others. Look it
> up.
> > > >
> > > > My GTI was running in ES on BFG R1s at another SFR event. My
> co-driver
> > > > sawed the wheel trying to catch a spin and got us up on two wheels.
> > > > I couldn't tell, but Katie Elder and other reliable witnesses said
> they
> > > > saw air under the tires. I did not like this. I lowered the car
> 1.25",
> > > > beefed up sway bars and moved to DSP. The car is now totally
> > > > uncompetitive, but is safer and a lot more fun to drive.
> > > >
> > > > What's the point? That vehicle/tire combos that roll with some
> > > regularity,
> > > > such as race rubber clad but otherwise stock VWs, BMWs, and various
> > > > econoboxes, are allowed to run events, but others that *may* be even
> > > less
> > > > prone to rollover provoke a knee jerk reaction like, "A Previa is
> not an
> > > > acceptable vehicle for Solo II"
> > > >
> > > > My suggestion: you can't easily measure CG during tech, but you can
> > > > measure outside dimensions. CG height can be conservatively
> > > approximated
> > > > as the midpoint between ground clearance (C) and height (H). Divide
> the
> > > > estimated CG height by the track width (T) and use that ratio as a
> > > > stability index.
> > > > C + H
> > > > ----- = stability index
> > > > T
> > > >
> > > > Pick a cutoff stability index that would exclude vehicles already
> known
> > > > to have a propensity to turn turtle (VWs, 3 series BMWs, etc).
> > > > And encourage vehicles over that ratio be excluded by the safety
> steward
> > > > on stability grounds, unless the vehicle is classed in the rulebook.
> > > > Perhaps my Previa could have been excluded on under this rule. So
> be
> > > it.
> > > >
> > > > Note that lowering a vehicle reduces both C and H. This correlates
> well
> > > > with what we all know intuitively.
> > > >
> > > > I'm not claiming this formula is perfect, but I think it's better
> than
> > > > excluding vehicles based on appearance.
> > > >
> > > > /Bill
> > >
> > >
> > >
> >
> >
>
|