Corvette ZO6: Great fun. Shame about the Ladder-frame.

A horrid drive at inconceivable cost, briefly punctuated by 1 or 2 amusing stats. One of these involves getting nowhere a few eye blinks quicker than a competitor.  Wow at the lackluster delights. If you want to save yourself from dropping 70 large at the same dealer that sells Aveos, get a forklift, put a Hemi in it, and stick a vibrator in your butt.  It’ll be nearly as fast, and just as safe. 

That’s my terse text opinion of the ZO6-optioned Corvette I drove for my latest DVD that you can watch below.  Then you can read at Youtube why I think my view seems in contrast to perhaps every Vette driver in the known Universe.  Also check out the dozens of riveting comments in the Q&A follow-up.  I did.  And I was riveted enough to spark this blog.

Apparently, my research on the latest 427 ci Corvette was plenty thorough in the olfactory department of intended drivers.  Among the dozens of facts presented,  a particular one stirred a biblically hot wind of dissension.   Clearly he’s incorrect, they must’ve carped, otherwise he’d be the first person in history to publicly present a proof of the C6 Corvette’s Ladder Frame chassis.

Understand,  a Ladder frame is what a tractor-trailer uses.  And a tractor. And a trailer. Its one of the oldest chassis designs in the world and it’s chief weakness lies in its wobbliness. Something tractors don’t mind. Trailers much either. They are also inherently less safe than uni-bodies, which comprise 99% of passenger cars in the world.   Here again, safety isn’t as much a concern for trucks as is the vehicles they crash into.

How can a car, touted by its parent as a world class SuperCar be designed with an antiquated truck frame?  GM calls it a ’spaceframe’. That sounds plenty modern.  Almost futuristic like its on the cutting edge of the engineering envelope.  And here comes that douchebag VanPala with his goddamn open-mindedness spouting smears without consensus.

Well, when we’ve been bamboozled long enough, its too painful to acknowledge we’ve been taken. Especially if the bamboozle has captured our ego. 

A persistent reader code-named, ‘Corvettably’, signed up just to entertain me with rumblings like, “The Corvette has one of the lowest personal injury claims. Sounds like a good safety record to me.”  Indeed. But this has nothing whatsoever to do with how the Corvette performs in a crash, and a lot to do with Corvette’s being driven less miles and less often than the average car.  He has ‘confused causation with correlation’.

Another of his musings, “The central section [tunnel] is more like the X-brace setup used by the Honda S2000.”  It shares a structure with a uni-body car therefore it can’t be a ladder, is what he was getting at.  Which is the common ‘Non-Sequitur fallacy:  failing to recognize alternative possibilities’.

On a Youtube video about the ZR1-optioned Corvette, I commented that ladder frames are inherently less safe [than uni-bodies].  A reader replied, “the Corvette has a 5-star safety rating.”  I emailed  ratings giver, NHTSA, who said they didn’t test the Corvette.  So I posted to the reader where he got ‘5 stars’ from.  My response, by having 6+ people click the thumbs-down icon, was spammed-out into deletion.  That’s not the scientific way.  That’s propaganda.  We need to be vigilant to people dismissing science simply because it doesn’t applaud their opinions.

In pickups, a  robust ladder is something of pride.  You see them at car shows stripped down to admire the beefy unidirectional beams conveying strength in towing and maybe some slight flexing for extreme offroad articulation.  But with sports cars, we want it light and stiff, and seeing it sitting there looking like a school bus is disturbing.

But strip it the GM way (remove only body panels, glass, and the interior) and you’ll be staring at what looks exactly like a Ferrari 599’s unitized ’spaceframe’ and nothing like a garbage truck’s ladder.  So, what’s going on here?

According to ‘The Race Car Chassis’ by Forbes Aird, we find that a Space-Frame can be best summed up as a structure with 4 properties:

1. Its composed of only straight-line elements.
2. All elements continually form planes of 3d polygons.
3. Every single element will only ever be loaded in either pure compression or tension.
4. All loads must enter/exit at junctions of 3 or more elements.

If you are inconsistent with just one, you are not a Spaceframe. The Corvette (C6) is inconsistent with all 4.  In fact, so far as I know, only  a handful of roads cars in the world have ever had SF’s.  Some say all road Ferrari’s before the F360 were Spaceframes.  But again, they’ve mistaken the (four-tube) Tube-chassis for a SF, since they lack one or more of our above properties.  In minimal form, the Ariel Atom is a SF and in purer forms, the Lamborghini Countach and the 1955 Mercedes 300SL Gullwing are SF’s.  The ‘gullwings’ weren’t there for beauty, but to cover the neccesary torso-high girder (upper chord) across all door openings.  Obviously impractical for road cars.

What a term though! It sounds like the Corvette is some technological tour de force GM designed in outer space. Keep in mind, while the Corvette is by no means a SF, your patio umbrella is. There is a test too, called the ‘ball joint’ test, that’s consistent with my video.  But we can call it a SF if we want - of course then we must also extend this rubric to pickup trucks as well.

Wow, VanPala is now proclaiming a web of conspirators including Ferrari, Audi, and Honda among others according to Wiki, and (via Press Release) GM, Dana, and Alcoa,  as bare-faced liars.  Well, a ’spaceframe’ is one of those funny words like ‘liberal’ and ‘plastic’ that generically means so many things due to its over use, especially in marketing.  Its folk taxonomy.

So, SF is idiom.  Further complicating matters, the guy who designed the damned thing (C5 Corvette), McLellan, calls it a backbone. Forget for a moment that the backbone chassis is so dangerous in side-impact safety dynamics that it makes the ladder look like NASA technology, it just has a ball-stomping ring to it, doesn’t it?  Like a fearless American counterpart to the monocoque.  If I’d designed something that badass sounding, I’d talk it up too.  Physics-wise, he’s lying.  However, Merriam-Webster defines backbone as, ‘a firm resolute character’.  Sure, I’ll go with that.

Not many will call McLellan on it since they’ll likely confuse the torque tube for the backbone. Porsche has been using torque tubes since the 928. Its good, it keeps some acceleration forces from being absorbed by the chassis. Its purpose in life is to control torsional loading as a suspension element and is by no means a load-bearing chassis component.

The only major chassis type left and that’s consistent with my DVD is the ladder frame.  You may find consistencies with uni-bodies like the Fiero.  But car chassis’ are hardly classified by structure, but instead by the way loads are channelled to the wheels. 

Stand on the roof (bow) of a Corvette.  Your weight splits in two – channelled toward each perimeter rail where it splits again into four with no more splits till the suspension, i.e., standing on a ladder; which is consistent with a 2D structure. 

Stand on a Porsche Boxster’s roll bar.  Your weight splits in two - channelled toward the unibody where it splits infinitely and gets channelled diffusely to the suspension, i.e., standing on an egg; which is consistent with a 3D structure.

As I see it, the only smoking gun authoritative enough to quell the Vette bigots is a CAD/CAM machine. I tried to rent one. They said no.

I’m better off.  Before an audience, lay down a ladder, flat, and nail a wheel to each corner.  The vast majority should agree, a ladder frame appears before them.  But a few will see a unibody, a monocoque, a backbone, a spaceframe, or whatever google tells them to.

My detractors are already warming up their comments, accusing me of arguing this whole spiel without a providing a single link to ‘proof’ from an authoritative source.  Even if the Detroit Editor of Motor Trend Magazine used the term ‘ladder frame’ in a writeup of the C6 Corvette at the top left of page 65 of the February 2004 issue, that wouldn’t be ‘proof’.  That’s simply adding to my consensus.

‘Proof’ in the traditional fanboy zealot sense of googling some official car chassis database is a little hard to come by.  Nothing like that exists.  In fact, there is no such thing as proof of anything.  Physics deals only with successive approximations to the truth.  Fortunately, we have brains (most of us).  

Using critical thinking we’ve seen that looks can deceive.  Absence of evidence is not evidence of absence.  Press Releases?  Useless. Public opinion?  Worthless.  And crucially, we’ve recognized some common and perilous fallacies of logic and rhetoric.

But don’t take my word for it.  I originally said, “The modern day Corvette uses a Ladder-frame chassis like a pickup truck.”  

Steve Wesoloski, GM’s Road Racing Group Manager in charge of the C6R Corvette race-car, said in an interview to Racecar Engineering Journal about designing a race car out of the (C6) Corvette ZO6, “Being a ladder frame, basically like a truck with the hydroform frame rails and some crossmembers, it is very tough to get the torsional stiffness.”

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