The Complex Engineering of Aston Martin’s DB11 Volante
If you were asked to name the craziest thing that ever happened to an Aston Martin inside a laboratory, you’d likely invoke some witty repartee between James Bond and Q. But that’s only because you don’t know how Aston’s engineering department developed the roof for the 2018 DB11 Volante.
The Volante, for those who don’t speak fancy, is the convertible version of the DB11, the excellent, $200,000 grand tourer that emerged from a new factory and major investments by an automaker that has spent the last century pivoting between glorious feats of engineering and bankruptcy. Like everyone who buys $200,000 convertibles, Aston Martin customers don’t like the idea of making any sacrifices for the right to feel their Hermès scarves flap in the wind coming off the Riviera.
Which is why, way back in 2014, Aston’s engineering team started designing a folding roof that combines the opulence and desirability of the coupe with the can’t-beat-coolness of a convertible. If you asked the overall-clad denizens of Ferrari, Jaguar, or Bentley about their convertibles, they’d likely say they put in just as much work. Because that’s what competing at this level of the auto industry requires when it comes to taming the beastly nature of the convertible.
You see, trading a plate of steel or aluminum for a piece of fabric that spends half its life stretched taut and the other half stuffed in a compartment is a great way to create problems. The roof must close itself (this isn’t a Mazda), which requires all sorts of complex mechanical bits and bobs. That inherently less-robust fabric has to stand up to pelting rain and heavy snow, maintain silence at highway speeds, and look as good after a decade of abuse as it did when it left the dealer lot.
“We don’t want the roof to devalue the car,” says David Hammerton, an Aston development engineer who helped lead the project. And no, a hard top was not an option here. There’s no way to pack it away without the creating the sort of silhouette-ruining bulge that would make an Aston Martin designer stick a clay modeling scalpel in their eye.
First, the team comes up with five or six concepts that might offer different ways to open and close the roof, and various folding strategies for when it’s stored for drop-top driving. The engineers consider how long it takes to open or close (that’s cycle time), the aesthetics of that process (aka choreography), rear visibility, mechanical complexity, cost, and how it fits with the rest of the car.
There are two basic ways to make a roof open and close. The first is the Z-fold, where the frontmost panel stays parallel to the ground, coming up like a cobra rising to strike. The mechanically simpler K-fold sends that front bit inverting on itself, flipping over backwards. That’s what Aston went for. Then you have to decide between a coupled and an uncoupled approach. In the former, the front bit of the roof latches onto the front header to tension the fabric. It’s easier, but also slower and less smooth that the latter, where the soft roof is pulled taut as it locks into place. Aston went for the uncoupled approach.
“We spent months looking at every single movement of the roof,” says Michael Ward, who led the convertible development. That includes improving on what they saw in flawed designs. The roof on the convertible version of the DB9, for example, would pause for a moment just before latching closed. “We saw that as an error state, and wanted to fix it,” Ward says. Mercifully, the DB11’s roof does not pause as its closes, even for an instant.
Once they get a design approved,the team builds a series of 15 or so prototypes. Because this is all happening alongside the development of the car itself, they have to settle for sticking these tops on what’s called vehicle bucks, which look like cars, just without wheels, doors, or an engine.
Then it’s on to testing, which is where things get fun, creative, and just a bit barbaric. To ensure the roof’s 500 parts, including a six-cylinder hydraulic actuator, can survive a lifetime on the road, engineers open and close it endlessly, aiming to cycle it up and down 6,000 times without a hiccup. They stick it in a wind tunnel to guarantee a driver in a very great hurry can open it up while driving at 31 mph (in case it starts raining and you simply cannot bear to pull over) and turning hard enough to pull 1G, as you might on Monaco’s curvier streets. They crank up the gust until the thing breaks, which, disappointingly, usually involves it just stopping mid-movement, not breaking off and flying away.
All the while, they’re on watch for what the pros call NHV—noise, vibration, and harshness. That means spotting and squashing any squeak or rattle from the roof’s many parts. Just to make things extra tough, the higher-ups allowed even less NHV for the Volante than they did for the coupe. They’re also watching for any sign of abrasion on the insulated, acoustic material that makes up the roof, which is designed to reveal no creases, even after hours sitting folded up.
For wind noise, they judge themselves by the “articulation index”: When you’ve go the roof up, do you have toraise your voice to be heard by your passenger, or crank up the volume to keep the Dvořák bumping? Then your loyal engineers have failed their mission. After all, Bond-worthy witticisms don’t sound as good when you’ve got to holler.
Once they’ve got an actual car to work with, the engineers head to the track with the roof closed, hit the 187 mph top speed, and open different windows to see how the fabric handles the beating. Any sign of flapping is unacceptable. When it’s not racing around, the car’s in Aston Martin’s climate chamber, where it suffers a variety of nightmares. The shower test mimics a car wash without the soap or brushes, blasting water at the roof to check for leaks. (In a show of faith, Ward and Hammerton sat inside for the first hosing.)
They throw sandbags on the roof to see how it handles the weight of fallen snow. They set it under solar lamps to see what a harsh sun does to the fabric, before taking it to Death Valley for a real life test. They drop the temperature to -4 degrees Fahrenheit and crank it up to 176 degrees, examining how the mechanical bits handle any place on Earth an Aston Martin customer might decide to drive.
Because unlike Q, the real engineers can’t blame rogue secret agents for Aston Martins that don’t hold up.