Oak Ridge National Laboratory displayed a 3D printed replica of the Le Mans-winning Shelby Cobra at the 2015 Detroit motor show.
On the show floor we spoke with Lonnie Love, group leader for automation, robotics and manufacturing at the lab, who told us all about the car, which has been made to show “where advanced materials, lightweight composites, new manufacturing processes are going”.
The car’s body shell and chassis are all 3D printed out of 20 percent carbonfibre-reinforced ABS plastic. The body consists of five major sections: the nose and tail, both of which are about 30 centimetres long; and the bonnet, passenger compartment and boot, which are all significantly larger pieces.
Just 12 bolts (six each at the front and rear) hold the whole shebang is held together. To access the drivetrain, some of the bolts have to be removed and body panels removed. Ingress and egress is ungainly as there are no functioning doors.
All up the car weighs around 680 kilograms, 205kg of which is accounted for by printed material.
At the rear there’s a 100kW electric motor, which is fed by a 110kg battery pack that resides under the bonnet. Thanks to the car’s low weight, the printed Cobra is good for a 0-60mph (0-96km/h) time of under five seconds and a top speed of around 130km/h.
From design through to the final product that we saw, this uniquely created Cobra replica took six weeks to complete. In total it took 24 hours to produce all of the car’s printed components.
To arrive at the final, almost completely flawless body work the car was sanded down, hand buffed and painted. We sat almost flawless because from 30cm away there’s a slight seam noticeable where the nose and bonnet meet, likewise where the boot and tail join up.
Unlike the Local Motors Strati, which almost revels in its obviously 3D printed nature, the Cobra replica only really betrays its origins in the passenger tub, the deliberately unfinished grille opening and on the bonnet’s black oak leaf, which is actually just clear coat applied over raw printed material.
This 3D printed Shelby Cobra replica looks so convincingly conventional that this writer was about to pass it by until he noticed a hastily done sign on the windscreen reading, “Yes! It’s a 3D printed car”.
Love says that, during the first day, his team were miffed as to why the car was getting so little attention. When they asked a passer-by, he admitted that he had no idea that it’s a 3D printed car.
According to Love, any changes to a 3D printed car, like this Cobra, would be easy to realise — just design the mods virtually, print them out and affix them.
As a case in point, the off-the-shelf roll bars had to be modified to fit the car’s mounting points that allow for slightly easier access to the drivetrain. Instead of designing a completely new roll bar, the team came up with 3D printed a metal elbow (in grey above), which could be fitted to the existing roll bars.