Taking a closer look at old tops

  • 01-May-2009 01:36 EDT
1 jet nozzles Karmann.JPG
The water booth is one of several tests available to Karmann Group test engineers. Long-range business plans call for Karmann Classics to provide full convertible top restoration services for all make and model vehicles.

A newly launched company for restoring softtops can leverage the testing and product development expertise of its namesake, the original manufacturer of Volkswagen Karmann Ghia and VW Beetle convertibles.

The more than 200,000 VW Beetle convertibles and 50,000 Karmann Ghia convertibles sold in the U.S. mean business opportunities for Karmann Classics, an aftermarket company located on the Karmann USA campus in Plymouth Township, MI.

"As the original manufacturer of the VW Karmann Ghia and the VW Beetle convertible, Karmann is uniquely positioned to rebuild convertible roof systems for these vehicles," said Erik Roeren, President and CEO of Karmann USA, part of the worldwide Karmann Group.

Karmann specialists will test every restored/repaired convertible top. "The top will be manually cycle-tested approximately 10 times to assure that the operating efforts and latching effort meet all of the expectations of Karmann," said Scott Somerville, Engineering Manager for Karmann Technical Development.

Newer vintage vehicles will undergo water testing via a vehicle drive-in booth fitted with 360 nozzles for high-powered water sprays. "The cycle time of the test is 8 min. Each nozzle is set at 31 (±2 psi) with a flow rate of 2.5 gal/min for a total of 900 gal/min," explained Somerville. "A filter is included within the water system to ensure particles do not exceed 50 microns."

Older vintage vehicles will be "hose-tested" for water leak detection.

Convertible top restorations are likely to encompass a variety of issues, such as fabric cuts as well as rust-deteriorated frame mechanisms. As such, Karmann engineers will accumulate plenty of information. "Karmann product and testing engineers will be able to see how a convertible top of considerable age has withstood several years of use. They will see roof system issues that resulted through a natural aging process and extended customer usage," said Somerville.

The real-life status of materials and coatings will be especially noteworthy to engineers. "We'll be particularly interested in learning how textiles, seals, as well as plastic and metal parts have aged from extreme amounts of environmental exposure. I foresee that our observations could lead to a re-evaluation of testing and design specifications for a variety of issues, including ultraviolet exposure, corrosion resistance, and life cycle testing," Somerville said.  

Germany's Karmann Group has restored more than 6000 convertible tops since 1985. Karmann USA and Karmann in Germany have designed, developed, and tested softtops and retractable hardtops for numerous vehicle manufacturers.

"Although the testing equipment at Karmann USA is not identical to equipment at Karmann Germany, the validation capability with regard to roof systems is identical," said David Graham, Supervisor of the Test Group at Karmann Technical Development.

Karmann in Michigan has a variety of testing equipment for life cycle durability (including programmable controllers and power supplies with 24-h digital video recorders), environmental evaluations (including environmental chambers for heat/humidity/cold exposure), and dimensional fit and finishing (including a full-vehicle coordinate measuring machine and a portable three-dimensional FaroArm), according to Graham.

"A number of tests are done that are specific to either a retractable hardtop or a conventional softtop. For example, hardtop testing typically includes an oil canning and dent test for exterior panels, while softtop convertible testing typically includes evaluations that are roof material/textile-related, such as evaluating the effects of extended storage with the top in a retracted position," said Graham.

Karmann USA, founded in 1996, is a subsidiary of Germany-based Wilhelm Karmann GmbH. Two of the most popular cars produced by Karmann are the VW Karmann Ghia (1955-1974) and the VW Beetle convertible (1949-1980).

Karmann USA's convertible-top production list includes the Chrysler Sebring, the Pontiac G6, and the Ford Mustang. 

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