Daihatsu Discloses Details of Copen Sports Convertible

Apr 10, 2014
Motohiko Hamada
The prototype of the Copen sports convertible
The prototype of the Copen sports convertible
[ If it clicks, the expanded picture will open ]
An X-shaped reinforcement reflected on a mirror placed under the vehicle facing right. The color of the floorboard is different from that of the reinforcement because this is a prototype.
An X-shaped reinforcement reflected on a mirror placed under the vehicle facing right. The color of the floorboard is different from that of the reinforcement because this is a prototype.
[ If it clicks, the expanded picture will open ]
The tank of the vehicle. The diamond patterns prevent buckling.
The tank of the vehicle. The diamond patterns prevent buckling.
[ If it clicks, the expanded picture will open ]

Daihatsu Motor Co Ltd showed a prototype of the Copen kei sports convertible to the press prior to its official announcement scheduled in June 2014.

Because the specifications of the vehicle had not been completely determined yet, stickers were attached to the outside of the vehicle for disguise. But Daihatsu prepared a slalom course, showing its confidence in the vehicle's drivability.

Currently, Daihatsu is not manufacturing cars in the Copen series. So, the new Copen will be "relaunched." But the company started to develop it in January 2010, when it was still selling the previous model.

"We would like you to consider it as a fully-remodeled version of the previous model," the company said.

This time, Daihatsu disclosed some of the technologies employed for the vehicle. Its outer panels are made of resin except for the doors. Because the outer panels of the production vehicle to be announced in June can be replaced, they had to be made of resin. But the company aimed to realize both replaceable outer panels and a lower weight. In fact, with the outer panels made of resin, the mass of outer panels was reduced by about 2kg from 5-6kg to 3-4kg.

Also, the interior appointments of the vehicle can be replaced. The company will announce details of it in June.

The front and rear fenders, front and rear bumpers, right and left rocker panels, fuel lid and hood outer are made of PP (polypropylen). The hood inner, roof, back panel, luggage, etc are made of SMC (sheet molding compound). Daihatsu employed SMC for horizontally-positioned parts to which a bending force is applied due to their own weights.

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In general, when resins are used for outer panels of a vehicle, all of them are made of resin including its doors like General Motors Co LLC's "Fiero." Daihatsu probably wanted to make all of the vehicle's outer panels by using resin, considering that the color of the vehicle will be changed by replacing outer panels. But it seems to have given up the idea this time.

The outer panels are fixed to steel parts with Torx screws, which function as an anti-theft measure, compared with hex screws. But wrenches for Torx screws are widely used now. So, there is still a risk.

The floorboard of the new Copen was designed based on the lower body of Daihatsu's "Mira e:S." Because the number of doors decreased from four to two and the outer panels are made of resin, the side panels were newly designed. Under the floor, an X-shaped reinforcement was added, and a transverse reinforcement was installed in front of the X-shaped reinforcement.

The thickness of the reinforcements is probably 2.3mm, which is about four times thicker than that of the original vehicle's reinforcements. In terms of stress distribution, it is close to the "X-shaped frame," which was used before the development of the monocoque structure. The reinforcements were attached to the floorboard with M10 bolts.

Furthermore, Daihatsu added another reinforcement that connects two places near the points to which a torsion beam is fixed. The company aims to prevent the auto body from being distorted by a transverse force applied to the points.

As a result, vertical flexural rigidity and torsional rigidity were improved by 200% and 50%, respectively, compared with the previous model of the Copen.