After several days with the new Rolls-Royce Dawn, the British luxury marque’s posh new $340,000, four-seat convertible, I realized the most striking feature isn't the smooth engine, intoxicating leather, or retractable hood ornament. It's the roof.
This came to me while watching the three-ton machine’s enormous fabric top---the largest of its kind in creation---retract into its cavernous bay behind the rear seats in nearly perfect silence.
The noises that usually accompany an automatic roof are absent. No straining of taxed electric motors, no shrill changes in pitch and volume as it cycles through every phase of retraction, folding, and stowage. No metal-on-metal grinding, no audible protest of stiff fabric roof being forcibly compacted. Just a few muted clicks to mark the start and end of the process, and a polite whirr from somewhere deep within the rear of the car.
It’s so whisper-quiet that a Dubai detective could spend an overnight stakeout opening and closing the thing, with no one the wiser. Military engineers, who struggle to mute their gear for battlefield stealth, should buy a Dawn and dissect it. (With its 6,000-pound curb weight and huge, torquey V12, they could also just drive the Dawn into battle. I’d enlist for that.)
Of course, having customers who happily shell out the price of a house for a car obliges you to flood every detail with mind-bending scrutiny. In this market, silence is a luxury.
With the Dawn, the British builder of chariots for the rich and famous insists on silence not just from within the cabin, but from everything. Just as the automaker employs engineers dedicated to making its stereo knobs wonderfully weighty interfaces, so too does it have teams striving for a roof that will purr rather than screech.
It's doubtful that anyone, anywhere, ever complained about their Rolls having an acoustically unacceptable roofs. But the company prides itself on staying ahead of customers’ wants and needs. Nobody complained about the knobs not being “weighty” enough, either, but why risk it?
The core of the process is a hydraulic system that moves all the roof’s linkages in a single motion, rather than a series of start-stop movements as each stage of the process begins and ends. This includes the opening and closing of the rear deck as it swallows the roof and the stacking of the horizontal elements, including the rigid metal frame, the fabric, and the glass window. All the stages work in a parallel process powered by six hydraulic valves. In a typical soft-top, the process occurs in steps, with each valve going through a sequence of jerky motions.
The Dawn's roof structure must accommodate that sort of thinking, so all the braces, supports, and collapsing skeletal bits are designed for seamless continuous movement. The electric motor driving the hydraulics---itself buried deep within the car and surrounded by sound-deadening materials to mute its activity---therefore operates at a more constant rate, without lots of winding up and down with each stage of movement. The single-motion process speeds things up too. The roof can open or close in just 22 seconds, even when the car’s going as fast as 31 mph.
Carefully selected materials help keep a lid on acoustics. The roof’s six-layer construction includes three layers of fabric and rubber on the exterior to provide weather sealing and insulation, and Rolls claims it offers 20 percent greater elasticity than similar designs. This allows it to return to its original shape without the audible straining you get from stiffer materials. (The sound-deadening interior layers and aerodynamic French seams throughout help minimize wind noise, so the interior is actually slightly quieter while driving than its hardtop sibling, the Wraith coupe.)
Because the roof material was engineered to be thin, lightweight, and flexible, it can fold into a space that’s the same as that designed for the roof of the petite BMW 2-Series convertible.
Less overall material, coupled with smoother engineering, makes this about as stealthy a roof as you can procure. The result is a robustly engineered system that feels as though it’s not even there. The Dawn’s roof glides away at your command and returns peacefully when you desire, without drawing attention or distracting you and your friends from the awesome day you’re undoubtedly having. In that respect, it’s pure Rolls-Royce.
