Convertible

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For the stock trading reference, see convertible security.

A convertible is an automobile body style with a flexibly operating roof that can convert between open-air or enclosed modes. Roof designs are highly variable from the folding textile roof, known variously as the top, soft top, ragtop or hood — to the folding multi-sectional rigid roof known as a retractable hardtop, coupé convertible or coupé cabriolet.

1 Folding textile roof
2 Retractable hardtops
3 Variations
4 History in the United States
5 Gallery
6 See also
7 References
8 External links

[edit] Folding textile roof

The collapsible textile roof section (of cloth or vinyl) over an articulated folding frame may include linings such as a sound-deadening layer (e.g.,Volkswagen Beetle) or interior cosmetic headliner (to hide the frame) (e.g.,Chrysler LeBaron) — or both — and may have electrical or electro-hydraulic mechanisms for raising the roof. The erected top secures to the windshield frame header with manual latches (e.g.,Mazda Miata), semi-manual latches, or fully automatic latches (e.g.,Volvo C70). The folded convertible top is called the stack.

[edit] Pros and cons

Convertibles offer the flexibility of an open top in trade for:

potentially reduced safety
poor break-in protection
deterioration and shrinkage of the sun-exposed textile fabric over time
diminished rear visibility, from a large roof structure, small rear window, or obstructed rear window — or all of these: e.g.,MINI convertible.
generally poor structural rigidity. Contemporary engineering goes to great length to counteract the effects of removal of a cars's roof. For example, a 2007 article in the New York Times, referring to the Volkswagen Eos, reported:

{{cquote|To neutralize the loss of torsional rigidity inherent in any convertible, VW engineers cleverly took the basket-handle roll bar of the VW Cabrio, inverted it and placed it under the rear seat pedestal. A beefed-up windshield frame of hot-stamped ultra-high-strength steel is connected directly to the floor pan’s reinforced frame rails. Steel tubing provides more stiffness behind the doors for an extra layer of safety. Partly as a consequence, rear seat passengers have about 10 inches less shoulder room than in the smaller Rabbit"^[1]

specifically poor structural rigidity, such as pronounced skuttle shake, a characteristic whereby the structural design of the bulkhead between engine and passenger compartment of a convertible suffers sufficiently poor rigidity to negatively impact ride or handling — or allow noticeable vibration, shudder or chassis-flexing into the passenger compartment.

[edit] Tonneau covers

Folding textile convertible tops often do not hide completely the mechanism of the folded top or can expose the vulnerable underside of the folded top to sun exposure and fading — in which case tonneau covers (British: boot) of various designs snap or secure into place to protect the folded roof and hide the mechanicals. Detachable foldable, rigid or semi-rigid covers require space-consuming storage inside the vehicle — and sometimes complicated installation from outside the stationary vehicle. Foldable vinyl and cloth covers can be prone to shrinkage, further complicating installation.

[edit] Evolution of the tonneau cover

The MKI (first generation) MGB (1964) roadster featured a manually-assembled convertible frame which required the driver to install the separate vinyl or cloth convertible top — from outside the car. Likewise, a similar detachable frame installed to support a foldable vinyl tonneau cover with a series of twenty press fit snaps.

Convertibles such as the Chrysler LeBaron (c.1988) used sleeve and groove systems to anchor foldable vinyl tonneau cover, again installed manually from outside the car. Later textile convertibles used semi-rigid plastic tonneau covers, e.g., the first generation Audi TT and Cadillac Allanté.

Convertibles such as the fifth generation of the Cadillac Eldorado featured a detachable two-part, fully rigid, manually installed tonneau sufficiently strong to support a seated person — also known as a parade boot.

Convertibles such as the second generation Mercedes SL popularized the integral manually operated self-storing rigid tonneau cover -- in its case accompanied by a separate removable hardtop. In either case, the design required manual operation from outside the stationary vehicle.

Convertibles such as first Porsche Boxster^[2], Toyota MR2 and third generation Mazda Miata (NC) featured Z-fold (aka zig-zag fold^[2]) tops, whereby the exterior of the neatly retracted fabric roof also protected the remaining roof from sun exposure — eliminating the aesthetic or protective need for a tonneau cover.

Convertibles such as the second generation Ford Thunderbird (1958) convertible and the fourth generation Mercedes SL popularized the complex electro-hydraulic roof mechanism that automatically secured the folded top under a rigid tonneau — button activated by a seated driver — and later more routinely available on convertibles such as the Volvo C70, Chrysler Sebring and Mitsubishi Eclipse Spyder.

The contemporary retractable hardtop convertible such as the Chevrolet SSR include tonneau covers that "self-store" the roof assembly.

[edit] Detachable hardtops

Convertibles such as both the first and eleventh generation of the Ford Thunderbird and the second and third generations of the Mercedes SL featured as standard or optional equipment fully rigid, manually installable hardtops — later examples including heatable rear windows. These hardtops provided acoustic insulation but also required space-consuming off-season storage — and a cumbersome two-person installation. The optional aluminum (i.e., lightweight) detachable hardtop for a Porsche Boxster weighed 51 lbs.^[2]

[edit] Convertible windows

Convertible side windows have evolved from non-existent in the earliest models, to detachable side screens and manually or power operated glass side windows. Rear-windows have evolved similarly, with plastic rear-windows appearing as late as the first generation Porsche Boxster. Contemporary convertibles and retractable hardtops feature heatable glass rear windows to maximize visiblity — though rear windows often can compromise visibility by their size, as with the case of the very small rear window and restricted visibility of the Mitsubishi Eclipse Spider. Plastic windows can degrade, fade, yellow and crack over time, diminishing visibility.

[edit] Windblockers

Windblockers, also known as wind screens or wind deflectors, minimize unwanted drafts from reaching the occupants — specifically cold air rushing from behind the passengers having been forced over the windshield then returning to the natural lower-pressure zone where the passengers sit. The passage of wind by the occupants can create significant noise in the process.

Mazda pioneered the windblocker with its Mazda RX7 convertible featuring an integral rigid opaque panel that folded up from behind the two seats. Current convertibles feature windblockers of various designs including detachable fold-up designs (e.g.,Toyota Solara), vertically retractable glass (e.g.,Audi TT), carefully designed minimal flaps (e.g.,Mazda Miata) — or other integrated wind controlling systems.

Mercedes currently offers a feature that routes a heating duct to the neck area of the seat on SLK and SL models, marketed as the "Air Scarf".

According to the chief engineer for 2008 Chrysler Sebring, Jim Issner, the windblocker for the Sebring reduces "wind noise by approximately 11 to 12 decibels."^[3]

[edit] Safety

Contemporary convertible design may include such features as electrically-heated glass rear window (for improved visibility), seat belt pre-tensioners, boron steel reinforced A-pillers, front and side airbags, safety cage construction — a horseshoe like structure around the passenger compartment — and roll over protection structures or (ROPS) with pyrotechnically charged roll hoops hidden behind the rear seats that deploy under roll-over conditions whether the roof is retracted or not.

Notably, the Volvo C70 retractable hardtop includes a door-mounted side impact protection inflatable curtain which inflates upward from the interior belt-line — vs. downward like the typical curtain airbag.^[4] The curtain has an extra stiff construction with double rows of slats that are slightly offset from each other. This allows them to remain upright and offer effective head protection even an open window. The curtain also deflates slowly to provide protection should the car roll over.

As an example of current convertible safety, the Citroën C3 Pluriel received the following European New Car Assessment Program (Euro NCAP) ratings:

Adult Occupant: , score 31
Pedestrian: , score 13

View: Citroën C3 Pluriel Encap crash testing

[edit] Retractable hardtops

The retractable hardtop solves some issues with the convertible, but has its own compromises, namely mechanical complexity, expense and more often than not, reduced luggage capacity. A 2007 Wall Street Journal article suggested "more and more convertibles are eschewing soft cloth tops in favor of sophisticated folding metal roofs, making them practical in all climates, year-round."^[5]

See main article: Retractable Hardtop

[edit] Variations

Convertibles have offered numerous iterations that fall between the first mechanically-simple but attention-demanding fabric tops to the highly complex modern retractable hardtops:

Roadster: Originally the term roadster suggested a minimal convertible, possibly with a frame that required actual assembly (i.e., not retracting) and separately installable soft "window" panels — offering little protection from inclement weather and requiring a time-consuming, complicated installation. A contemporary roadster is a two-seater convertible.

Landau & Rigid Door: Citroën's early Citroën 2CV featured a roof that rolled back on itself leaving rigidly framed side doors in place — followed in concept by such cars as the 1950 Nash Rambler Convertible Coupe.

Citroën currently markets the C3 Pluriel (Pluriel is a cognate with the English plural), which can be configured into five iterations, hence the name: ^[6]

a hatchback with a multi-layer insulated top.^[7]
a full-length "landau" sedan, operable partially or to the back window or any stage in between, with a buffet-minimizing wind deflector over the windshield.^[7]
a semi-convertible, with the roof open to the back window, the roof assembly folds into a well in the trunk floor.^[7]
a full convertible, whereby roof side rails are unlatched and removed^[7].
a roadster pick-up, where the back seats fold to a pickup-like bed with a drop-down tailgate.^[7]

View: Citroën C3 Pluriel diagram

The Four Door: A four door converitble is referred to as a phaeton, while a two-door is referred to as a cabriolet. Modern 4-door models, e.g., the Lincoln Continental, c.1960.

Peugeot presented the a concept four-door retractable hardtop convertible, the Peugeot 407 Macarena in 2006.^[8] Produced by French coachbuilding specialist Heuliez, the Macarena's top can be folded in 60 seconds, ^[8] with a steel reinforcing beam behind the front seats incorporating LCD screens for the rear passengers into the crossmember. ^[8]

View: Peugeot 407 Macarena, in action.

All-Wheel drive: AMC offered a four-wheel drive Eagle with a steel targa bar and removable fiberglass roof section — and other Sport utility convertibles such as the Jeep Wrangler offer four-wheel drive and a manually folded top. Audi offers the all-wheel drive A4 Cabriolet.

Drophead Coupe, Cabriolet or Cabrio: A type of convertible with only two doors ^[9] and thereby recalling the cabriolet carriage. With its Mazda RX7 convertible, Mazda introduced a two-seater convertible with a removeable rigid section over the passengers, removable independently of power operated textile section behind with heatable glass rear window. During the 80's, Jaguar produced an XJ-SC with two removable panels over the front seats and a partial fold-down convertible section in the back. It retained the rear side windows of the coupe and had fixed cant rails above these and the door glass. This allowed an almost full convertible with roll over safety.

[edit] History in the United States

Until the 1910 introduction by Cadillac of the first closed-body car, the convertible was the primary body style. US automakers manufactured a broad range of models during the 1950s and 1960s — from economical compact-sized models such as the Rambler American and the Studebaker Lark to the more expensive models such as the Packard Caribbean, Oldsmobile 98, and Imperial by Chrysler.

Threatened rollover safety regulations in the mid-1970s led to diminished popularity by the 1970s. In 1976 Cadillac marketed the Eldorado as "The last convertible in America". During this period of very low convertible production, T-tops became a popular alternatives.

Elsewhere globally, convertible production continued throughout this era with models such as the Mercedes SL, the VW Beetle Cabriolet, the VW Golf Cabriolet, and the Jaguar E-type.

In the 1980s convertibles such as the Chrysler LeBaron and Saab 900 revived the body style in the United States — followed by models such as the Mazda Miata, Porsche Boxster, Audi TT and later retractable hardtop models.

[edit] Gallery

Volkswagen New Beetle c.2008, with raised textile (cloth) convertible top featuring interior headliner, an acoustic insulation layer, and heatable glass rear window	Jaguar XK120 Roadster c.1950, with a very light weight canvas top and removable side curtains screwed to the doors — with no external door handles (shown: top stored)	Chrysler LeBaron c. 1989, with manually installed "metallic" vinyl tonneau cover, color-matching to the car body, secured with a 'sleeve and groove' system	Jaguar XK8 c.2008, with heatable glass rear window and fully automatic cloth top with integral top-concealing rigid tonneau	MG TD c.1953, with manual soft top and manually detachable sidescreens with clear plastic windows and Perspex rear window
Porsche Boxster c.2004, with detachable clear plastic windblocker and a Z-fold top, automatically raisable in 12 seconds^[2]	c.2005, Porsche Boxster and 911 convertibles with with tonneau-cover-eliminating Z-fold tops	Daihatsu c. 2001, a retractable hardtop convertible marketed in Japan in the ultra-compact Kei class	Rolls Royce Corniche c. 1986, a high-end prestige marque with a manually installed tonneau cover	Ford Model T c. 1925, with minimal weather protection
Cadillac Eldorado c.1959, with zipper operable clear plastic rear window	Cadillac Allanté c.1993, with detachable, rigid plastic tonneau cover. Built in Italy by Pininfarina, completed bodies were flown to the US 56 at a time in specially equipped Boeing 747's with final assembly at Hamtramck, Michigan. ^[10]	Nash Rambler Convertible "Landau" Coupe c.1950, with retracting roof and rigid doors, featured car of Lois Lane of the 1950's television series Adventures of Superman ^[11]	Volvo C70 c.2007, retractable hardtop in action, requiring 6.5 feet of vertical clearance during retraction^[12]	Cadillac XLR c.2007, with fully retracted aluminum hardtop concealed by self-storing tonneau cover, the hardtop manufactured by a supplier joint venture of Mercedes-Benz and Porsche.^[13]
Background: Peugeot Éclipse Décapotable, c. 1935, the Georges Paulin patented automatic folding roof, the first production retractable hardtop convertible, shown in action	Citroën C3 Pluriel c.2007, a multi-configurable convertible with roll-back textile roof and removeable rigid sidebars^[6]	Saab 900 c.1970, with manually installed semi-rigid tonneau	Citroen 2CV c.1975, with roll-back roof and rigid doors	Lincoln Continental c.1966, 4-door with integral automatically operating, self-storing tonneau
Cadillac Eldorado c.1971, with detachable, two-part, fully rigid "parade boot" tonneau cover	Mitsubishi Eclipse Spyder c.2004, with heatable glass rear window and restricted visibilty	Mercedes SL c.1963, with detachable hardtop, requiring twice-annual manual removal and installation — and space-consuming off-season storage of the hardtop	Jaguar E-type c.1970, with vinyl folding top — tonneau not installed, ranked first in Daily Telegraph list of the "100 most beautiful cars" of all time[1]	Jaguar E-type c.1970, with vinyl foldable tonneau installed and snap-secured
MINI Cooper, c.2006, with large blindspots from the top itself, small rear window, and interior rear roll hoops severely obscuring the driver's rear view	Maserati Spyder