Gull-wing door

The design can be a very practical one in a tight urban parking space. When properly designed and counterbalanced, they require little side-clearance to open (about 27.5 cm or 11" in the DeLorean) and allow much better entrance/egress than conventional doors. The most obvious downside to having gull-wing doors is that, were the car to roll over and come to rest on its roof, exit by the doors would be impossible, requiring a large windscreen opening to escape. The Mercedes SLS solved this problem by fitting explosive bolts in the hinges, which would blow up if the car rolled over, causing the door to fall off altogether. The Volvo YCC, a concept car designed by and for women, had gull-wing doors as part of its design. Gull-wing doors make it easier to lift a bag to store it behind the driver's seat, increase visibility over the driver's shoulder, and make it easier to get in and out of the car. The Tesla Model X, introduced in 2015, has double-hinged gull-wing doors, called falcon-wing doors by Tesla. The Model X has several design considerations to make the doors more practical. Being double-hinged allows them to open with less clearance (horizontal and vertical) than would otherwise be required. The vehicle also has sensors to determine ceiling height and the presence of potential obstacles and to determine how the hinges will operate to open the doors and avoid obstacles, if possible. == Design challenges ==

Gull-wing doors have a blemished reputation, largely because of early examples like the Mercedes and the Bricklin. The 300 SL used the gullwing design because its tubular frame race car chassis had a very high door sill, which, in combination with a low roof, would make a standard door opening very small. Mercedes engineers solved the problem by opening a part of the roof. The Bricklin had a more conventionally sized door, but the actuation system was unreliable in day-to-day use until an aftermarket air-door upgrade was installed in all Bricklins. In addition, there was speculation that in making the doors as light as possible, they wouldn't provide adequate protection in side-impact accidents. The DeLorean solved these problems by using a patented cryogenically set stainless steel torsion bar spring (manufactured by Grumman Aircraft Engineering Corporation) to partially counterbalance a full-sized door, and then added a gas-pressurized (pneumatic) strut similar to those found in hatchback cars. The combination of the torsion spring and strut provided the necessary torque to offset the torque of the door, as it opened through a rotational angle of about 80 degrees. The torsion bar is most important in the first foot of movement from the bottom, where the geometry of the strut is pointed at the hinge and therefore at a mechanical disadvantage. The spring relaxes as the door rotates open, and the strut gains a better moment arm and gradually takes over the effort. A correctly balanced door opens fully on its own by simply activating the door latch from the interior, exterior, or from an aftermarket wireless release. Other disadvantages of the system were not so easy to address. For example, the gull-wing design for a convertible version of a car is not possible, as the hinges would be removed with the roof, and standard doors would be needed for a convertible. Mercedes did so when replacing the gullwing coupe altogether with the 300SL roadster in 1958. It was never a concern for DeLorean, since no convertible version was ever planned. Sealing the car against water leaks and snow intrusion is more difficult because of the shape and movement path of the door itself. == List of models ==

This is a (partial) list of cars with gull-wing doors: Production cars • Apollo Intensa Emozione • Aston Martin Valkyrie • Autozam AZ-1 (Suzuki Cara) • Bricklin SV-1 • Bristol Fighter • Bugatti Type 64 • De Tomaso Mangusta (engine compartment) • DMC DeLorean • Gumpert Apollo • HiPhi X (rear passenger doors only) • Hofstetter Turbo • Hyptec HT (rear passenger doors only) • Isdera Imperator 108i • Marcos Luton Gullwing • Marcos Xylon GT • McLaren W1 • Melkus RS 1000 • Melkus RS 2000 • Mercedes-Benz 300SL • Mercedes-Benz SLS AMG • (NSU) Thurner RS • Pagani Huayra • Porsche 906 • Tesla Model X (rear passenger doors only) Image:Gumpert Apollo Dubai.jpg|Gumpert Apollo Image:Melkus RS1000.JPG|Melkus RS 1000 File:Model X vs. DeLorean.jpg|Tesla Model X (and the DMC DeLorean in the background) File:1993_Autozam_AZ-1_front.jpg|Autozam AZ-1 Kit cars Gullwing doors are common in kit cars, and many are not included on this list: • AMT Piranha • Bradley GTII • Dare DZ • Eagle SS Mk1 • Elite Enterprises Laser 917, inspired by the Porsche 917 • Embeesea Charger • Fiberfab Aztec 7, an American replica of the Italian Alfa Romeo Carabo concept car. • Fiberfab Caribee/Banshee • Illuminati Motor Works Seven • Innes Lee Scorpion K19 • Pelland Sports • Replicar Cursor • RPB GT • Burton Car Company hardtop • Siva S160 Spyder • Ultima Mk1 • Ultima Mk2 • Ultima Mk3 • Ultima Sport • Ultima GTR Concept and non-production cars • Aston Martin Bulldog • BMW Nazca C2 (windows only) • BMW Turbo • Chevrolet Aerovette • Ford Cougar 406 • Ford Evos (concept) • Isdera L'Aquila • Isdera Commendatore 112i (doors and engine compartment) • Isdera Commendatore GT • Isdera Erator GTE • Lamborghini Marzal • Lexus LF-30 • Lincoln Navigator Concept (2018) • Mercedes-Benz C111 • Mercedes-Benz C112 • Mercedes-Maybach 6 • Mercedes Vision One-Eleven • Pontiac Trans Sport concept (rear doors only) • Porsche Tapiro • Quant E • Quant F • Volvo YCC == Aircraft ==

• Cessna 350 • Diamond DA62 • Socata TB • Beriev Be-103 • Stoddard-Hamilton Glasair II • Dornier Seastar == See also ==