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Sep 19, 2013 at 03:47 PM
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The DeltaWing: A Clever Engineering Answer. But What Was the Question? Print
Written by Mike Fuller   
Apr 18, 2012 at 12:43 AM

So the DeltaWing stayed on after the 12 Hour and finally put in some testing miles.  Prior to that they only had about 100 miles worth of shakedown on the chassis.  But at the moment the DeltaWing group is on full lock down with nary a word about how the test went, how fast the car is, etc.  Yes, I've been told a thing here or there, and frankly, the times discussed certainly sound promising.  But without anything to put forth as verified it means we'll have to supplant fact with opinion for now.  And for those that know Mulsanne's Corner, rarely do I stray into this territory as too often you'll get caught up in all the PR hyperbole and start sounding like a real shill.  So as an exercise, I'll play devil's advocate, though working within the facts as available.

Let's start with those first.  In brief, the problem that the DeltaWing is designed to address is, with ever diminishing fossil fuel resources, how can we continue to race at reasonable racing speeds if we substantially reduce engine power in recognition of those diminishing resources?  The DeltaWing runs a measly 1.6 liter, 4-cylinder, turbo outputting only 300 hp.

So in order to achieve competitive lap times with only 300 hp two things needed to occur.  First off, to have a comparable power to weight ratio the DeltaWing needs to weigh substantially less, about half as much, than a contemporary LMP1.  And with that in mind, DeltaWing comes in at 475 kgs.  Bowlby has achieved this extreme weight reduction at very low cost; DeltaWing weighs around F1 levels but for what must be a very modest budget.  All of this via chassis architecture, not through uses of "unobtanium."

And it has a very unusual chassis architecture to say the least.  Think of the DeltaWing as a 3 wheeler, getting rid of the 4th wheel immediately removes weight out of the budget (one less upright, suspension, etc.).  Yes, DW does have 4 tires, but the fronts are a mere 4" wide each given the vastly reduced front tire loading.  Thus the two tiny fronts weigh about as much as a single conventional tire. This also means the uprights are much smaller, brakes, suspension, everything is reduced in size at the front given the reduced loadings as the DeltaWing's  chassis layout places 70% of the car's weight distribution on the rear wheel center line.  

DeltaWing's narrow front track (about 24" wide) also plays into the weight reduction.  Without the need to space 4 wheels out in conventional locations, suspension lengths are reduced, but more importantly, the structural requirements are lessened as there is minimal lateral weight transfer at the front (it all occurs in the rear) and no need for massive torsional rigidity.  The need to take large torsional loads into account means more structure.  And if you can do the opposite of that, less structure equals less weight.

The second part of making DeltaWing work is a huge reduction in aerodynamic drag.  This is achieved through a reduction in frontal area, but also through the elimination of any wings.  The narrow front track plays a part as well by allowing a particularly efficient underbody intake, assuming good management of the front wheel wakes, as all of the car's downforce is generated from the underfloor design.  The end results being roughly 500 lbs of drag for 2500 lbs of downforce at 200 mph.
       
All in all it is very clever engineering.  But, if you believe everything you read about the DeltaWing: it slices, dices, it is the solution to world hunger, in addition to gobbling up pollution as it goes around the track.  The DeltaWing is a new design methodology for the car, so sure, calling it innovative can be construed as a true statement. But we have to be careful about skinning the cat using an alternative method and then calling it an eagle.

And the reason I say that is that for all its Rubegoldbergian solution, DeltaWing's ultimate conclusion is simply better gas mileage.  And then the question has to be asked, if a current LMP1 gets 5 mpg, so what if DeltaWing gets 10 mpg?  The current CAFE standard is 27.3 mpg.  This goes to 54.5 mpg in 2025.  How is 10 mpg "relevant" to 27.3, much less 54.5 mpg?  It isn't.  
 
Now there is some argument to be made that the quickest way to achieve the higher CAFE standards will be lighter cars (not necessarily hybrids),  the American sedan has certainly become unnecessarily bloated and gas mileage has subsequently tanked.  The DW does execute a clever solution to achieve a lighter weight.  But can anyone really see a 5 passenger sedan using the same layout as DeltaWing?

But let's face it, light weight composites have been around for approaching 50 years.  And while they've been embraced and developed by the aerospace and motorsports industries, the road car industry has been loath to implement them on a mass scale.  The accounts have cried, "Too expensive!"

That's why we really need to be careful about talking about technology transfer.  As one motorsports engineer put it to me, "The Delta wing has no new or unique technology that is transferable to production cars.  So it is a dead end in car design."  The reality is that a majority of the design and manufacturing work that goes into creating a LMP car is done by private outfits with no ties whatsoever to manufacturers other than the contract to design and build the LMP car (think Dallara, Wirth Research, Lola, OAK Racing, etc.).  Sure, there are a few exceptions, but frankly the transfer is often one way and the opposite of what you think!  Regardless, remember, it's win on Sunday sell on Monday.  No engineer ever said those words.  However, down the hall in sales and marketing...

Yes, the conversation has shifted; I have no doubts that DeltaWing works.  But we now have to think hard; what do we do with it?  Looking past the desire to immediately monetize the concept, DeltaWing's greatest impact might simply be the stimulation of thinking about the future of the car, sportscar racing, and motorsports in general.  But perhaps the greater question is, does motorsport have to really have to be relevant?

Want to know more about the technology of modern ACO, IMSA and Can Am racing prototypes? If you do, there's  no peer to Mulsanne's Corner. Check it out at
http://www.mulsannescorner.com/

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