Retractable hardtop

Peugeot 402 Eclipse Decapotable (1938)

A Volvo C70 with retractable hardtop

A retractable hardtop, also known as coupé convertible or coupé cabriolet, employs an automatically operated, multi-part, self-storing hardtop in lieu of a folding textile-based roof.

Documentation indicates that an American engineer Ben P. Ellerbeck explored the idea of a retractable hardtop as early as 1919 — going so far as to prototype a manually operated system in 1922 that ultimately never reached production.^[1] Frenchman Georges Paulin subsequently designed the production 1934 Peugeot 601 Éclipse manually retractable hardtop, followed by the 402 Éclipse Décapotable.^[2][3]

Advances in electronics, hydraulics, and weatherproofing materials have made the modern retractable hardtop increasingly popular. Ease, enclosed car quality climate control with the top up, improved crash resistance, and passenger compartment storage security are traded off against increased mechanical complexity and expense and, more often than not, reduced luggage capacity.

A 2006 New York Times article suggested the retractable hardtop may herald the demise of the textile-roofed convertible,^[4] and 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]

History

Closing of the retractable hardtop of a BMW 3-series (E93)

Peugeot Éclipse Décapotable Background: the Georges Paulin patented automatic folding roof in action

1934 Peugeot 601 C Eclipse

1919 Ben P. Ellerbeck conceived a retractable hardtop – a manually operated system on a Hudson coupe that allowed unimpeded use of the rumble seat even with the top down^[1] – but never saw production.^[6]

1935 Peugeot introduced the first production, power-operated retractable hardtop in 1935, the 402 Éclipse Décapotable,^[4] designed and patented by Georges Paulin.^[4] The French coachbuilder, Marcel Pourtout, custom-built other examples of Paulin's designs on a larger Peugeot chassis as well.^[4] The first Eclipse 402s offered a power-retractable top, but in 1936 was replaced by a manually operated version on a stretched chassis, built in limited numbers until World War II.^[1]

1941 Chrysler introduced a retractable hardtop concept car, the Chrysler Thunderbolt.^[1]

1953 Ford Motor Company spent an estimated US$2 million (US$17,718,905 in 2016 dollars^[7]) to engineer a Continental Mark II with a servo-operated retractable roof. The project was headed by Ben Smith, a 30-year-old draftsman.^[8] The concept was rejected for cost and marketing reasons.^[1]

1955 Brothers Ed and Jim Gaylord showed their first prototype at the 1955 Paris motor show,^[9] but the car failed to reach production.

1957 Ford introduced the Skyliner in the United States. A total of 48,394 were built from 1957 to 1959.^[1] The retractable top was noted for its complexity and usually decent reliability^[10][11] in the pre-transistor era. Its mechanism contained 10 power relays, 10 limit switches, four lock motors, three drive motors, eight circuit breakers, as well as 610 feet (190 m) of electrical wire,^[1] and could raise or lower the top in about 40 seconds. The Skyliner was a halo car with little luggage space (i.e., practicality), and cost twice that of a baseline Ford sedan.

1989 Toyota introduced a modern retractable hardtop, the MZ20 Soarer Aerocabin. The car featured an electric folding hardtop and was marketed as a 2-seater with a cargo area behind the front seats. Production was 500 units.

1995 The Mitsubishi GTO Spyder by ASC was marketed in the U.S.^[6] The design was further popularized by such cars as the 1996 Mercedes-Benz SLK.^[4] and 2001 Peugeot 206 CC.

2006 Peugeot presented a concept four-door retractable hardtop convertible, the Peugeot 407 Macarena.^[12] Produced by French coachbuilding specialist Heuliez, the Macarena's top can be folded in about 60 seconds.^[12] It has a reinforcing beam behind the front seats which incorporates LCD screens into the crossmember for the rear passengers.^[12]

2006 Pontiac introduced a retractable hardtop version of the G6. The roof featured a relatively simple two-piece folding design and did not materially reduce rear seat space, although luggage capacity was severely reduced with the roof lowered. Production continued through the 2009 model year.

Construction

Retractable hardtops can vary in material (steel, plastic or aluminum), can vary from two to five in the number of rigid sections and often rely on complex dual-hinged trunk (British: boot) lids that enable the trunk lid to both receive the retracting top from the front and also receive parcels or luggage from the rear – along with complex trunk divider mechanisms to prevent loading of luggage that would conflict with the operation of the hardtop.

Variations

• The Volkswagen Eos features a five-segment retractable roof where one section is itself an independently sliding transparent sunroof.^[5]
• The Cadillac XLR features a retractable aluminum hardtop requiring 6 ft 10 ¹⁄₂ in (2 m) of vertical clearance during retraction, and manufactured by a supplier joint venture between Mercedes-Benz and Porsche.^[13]
• The Mercedes SL hardtop features a glass section that rotates during retraction to provide a more compact "stack."
• The Mazda MX-5 has been available since the 2006 model year with an optional power retractable hardtop, in lieu of the standard folding-textile soft-top. The cost of the retractable hardtop is actually less than the price premium charged to a separate hardtop. Compared to the regular soft-top, the hardtop weighs 77 lb (35 kg) more yet has no reduction in cargo capacity.^[14] The MX-5 is one of the few cars offering both hardtop and soft-top convertible choices, so it is possible to make a direct performance comparison; the hardtop has slower acceleration but a higher top speed. The hardtop roof is constructed of polycarbonate and manufactured by the German firm Webasto.^[15]
• Daihatsu marketed the Copen in the ultra-compact Japanese Kei class.
• The Chrysler Sebring's (and its successor the Chrysler 200's) retractable hardtop also is marketed alongside a soft-top. According to development engineer Dave Lauzun, during construction, the Karmann-made tops are dropped into a body that is largely identical: both soft-top and retractable feature the same automatic tonneau cover, luggage divider and luggage space.^[16] The retractable does feature an underbody cross-brace not included in the softtop.
• The Volvo C70, its retractable hardtop manufactured by Webasto^[15] includes a global window switch that allows simultaneous raising or lowering of all windows,^[17] and a button to power-activate the raising of the folded top stack within the trunk to access cargo below.^[17]
• The Vauxhall/Opel Astra TwinTop, is a three-piece retractable hardtop.

Pros and cons

The retractable hardtop convertible trades higher initial cost, mechanical complexity and, with rare exception, diminished trunk space, for increased acoustic insulation, durability, and break-in protection similar to that of a fixed roof coupe. The tops are also usually heavier than a comparable fixed-roof vehicle or a soft-top convertible, due to the increased strength required for the roof and more complicated roof mechanism, resulting in a potential marginal decrease in performance and fuel economy.

Pros

The retractable hardtop's advantages include:

• more weatherly than fabric tops when up
• more secure than fabric tops^[5][18]
• increased structural rigidity over a soft-top.
• eliminates the need for a tonneau cover
• no UV fading of underside
• eliminates removal and reinstallation of detachable hardtop
• may enable consolidation/simplification of a manufacturer's car lineup; for instance the current BMW Z4 (E89) is offering only as a coupé-convertible (hardtop), compared to the preceding E85 generation that had separate coupé and cabriolet (soft-top) variants.
• more attractive than fabric tops.^[18] A 2006 New York Times article suggested the retractable hardtop may herald the demise of the textile-roofed convertible,^[4] and a 2007 Wall Street Journal article suggested "more and more convertibles are eschewing soft cloth tops in favor of sophisticated folding metal roofs".^[5][19]
• Hard-tops generally have better visibility than soft-tops when the roof is up.^[20]

Cons

1958 Ford Fairlane 500 Skyliner during conversion

In addition to higher initial cost, increased mechanical complexity, and potentially higher repair cost, hardtop cons include:

• Potentially diminished passenger and trunk space compared to a soft-top convertible. Indeed, some hardtops have a nearly unusable trunk once the top is lowered.^[21][22][23]
• Higher weight and center of gravity than soft-top convertibles, reducing handling. The Audi R8 Spyder, Porsche Boxster and 911 Cabriolet have retained soft-tops. Audi has yet to produce a hardtop convertible as of 2011, since they include quattro as standard equipment in their convertibles (after the discontinuation of the 2007 Audi A4 2.0T cabriolet) which already adds extra weight.^{[21][22][23][24]}
• Decreased structural rigidity compared to a fixed-roof coupe. The 2010 Infiniti G37 Convertible tries to solve this problem with a folding steel roof, however this adds considerable mass to the vehicle.^[18]
• Potential need for more than minimum vertical clearance. For example, the Volvo C70 requires 6.5 feet (2 m) of clearance during operation.^[25] The Cadillac XLR requires 6 ft 10 ¹⁄₂ in (2 m) of vertical clearance.
• Potential need for more than minimum car footprint. For example, the Mercedes SLK's trunk lid extends rearward while lowering or lifting the top.
• Possible simultaneous engine and battery failure preventing complete roof cycling. Volvo includes an emergency roof cover with each Volvo C70.^[25] The Cadillac XLR owners manual contains seven pages of detailed instructions on how to manually lift the top. This problem is not unique to retractable hardtops since some soft-tops rely on battery power as well.
• Potential weather intrusion at seams

List of retractable hardtop models

Early models

Later models

Gallery

• 

  Mazda Miata Power Retractable Hard Top (PRHT) c. 2007, with 77 lb (35 kg) polycarbonate hardtop and identical cargo capacity to the soft top version^[1]

• 

  Cadillac XLR c. 2007, with fully retracted aluminum (i.e., lightweight) hardtop concealed by self-storing tonneau cover, the hardtop manufactured by a supplier joint venture of Mercedes-Benz and Porsche^[2]

• 

  Daihatsu Copen c. 2001 with retracted hardtop, qualifying for the ultra-compact Japanese Kei class

• 

  Ford Focus CC c. 2006 with its roof retracted, its final assembly performed by Pininfarina

• 

  Chevrolet SSR c. 2004, a retractable hardtop convertible pickup truck, its top engineered by ASC

• 

  Volkswagen Eos c. 2007, the five-segment top features an independently sliding sunroof, made by OASys

1. ^ Cite error: The named reference autoweek.com was invoked but never defined (see the help page).
2. ^ Cite error: The named reference mtrend was invoked but never defined (see the help page).

References