Indiana University-Purdue University Indianapolis (IUPUI) professor Andrew Tovar has taken his interest in using solutions found in the natural world to improve human engineering to the next level. His design for an automobile frame based on a human rib cage recently won an international automotive design competition. He started working on his design for the competition back in November 2014, and was excited about the opportunity to merge 10 years of research on automotive crashes with his interest in mimicking biological structures in man made objects.
Tovar is an assistant professor of mechanical engineering at IUPUI and director of the schools Engineering Design Research Laboratory. He says the competition “was a new challenge for me, going from component design to full-vehicle design. A very interesting challenge.”
The contest – put together by Local Motors – a Chandler, Arizona-based car company pioneering the use of 3D printing in automotive production, and the Advanced Research Projects Agency—Energy, a federal-government organization – was called the Lightweighting Technologies Enabling Comprehensive Automotive Redesign (LITECAR) Challenge. Basically, the challenge was for designers and engineers to come up with a lightweight but safe automotive design.
Tovar and his graduate student team competed against 250 teams from all over the world, and in the end Tovar’s design was chosen and he received the $60,000 grand prize.
His winning vehicle was designed to mimic the shape of a raindrop, a naturally aerodynamic shape. The vehicle is about 20 percent lighter than a conventional vehicle of the same size due to its internal structure which is composed of a lattice of aluminum-alloy support struts similar to the design of a human rib cage. The internal structure is covered with a polymer composite ‘skin’. The rib cage design not only allows the car to be lighter in weight, but also gives the body of the car tremendous strength and crash resistance.
Tovar calls his rib cage internal structure – WaterBone. The tubular steel roll cages are similar to those used in racing cars, but WaterBone employs innovative new materials, manufacturing techniques and algorithms.
Tovar said, “This is a bio-inspired design algorithm.”
Four IUPUI graduate students helped Tovar develop and design these algorithms and run computer crash simulations all in the service of designing a lightweight car, using nature inspired solutions, that was also tough enough to survive crashes .
Head of product development for Local Motors and one of the judges of the competition, Alex Fiechter said that Tovar’s design revolutionized the basic tenets of automotive design while still maintaining the basic safety, fuel economy and lightweight structure that the contest was looking for.
Fiechter said, “People have thought around the idea of an exoskeleton before, but the way he’s approaching the material that the skeleton is made of, and the way he’s configured it, is what really brought it all together.”
Racing cars have utilized steel-frame skeletons for years, but the amount of welding and the time that is required to build these frames make it very difficult and expensive to bring this kind of vehicle design to the mainstream. Tovar get’s around some of these extra costs by positing the use of large scale 3D printing in manufacturing his design. Additive manufacturing can take custom designed computer models of parts and build them layer by layer, throwing out the need for milling the parts out of solid metal. Using this large scale 3D printing technology, Tovar could hypothetically cast his car frame in one piece.
Fiechter explains, “Additive manufacturing definitely makes sense with a structure this complex. That’s definitely where he’s (Tovar) deriving some of his strength-to-weight savings.”
The rib cage frame would weigh in at 295 pounds, 10-20 percent lighter than a similar five passenger vehicle like the Honda Fit. Tovar estimates that when the car is all put together, it would weigh in around 2,400 to 2,500 pounds. This is lighter than a Honda Civic which weighs anywhere from 2,700 to 3,000 pounds. Tovar and his team have yet to actually build one of these vehicles, but he has used 3D printing to construct several small models of the car and is currently working with Indianapolis-based 3D Parts Manufacturing to develop metal powders and multi-material products to build his prototype.
Tovar is committed to seeing this project through and has invested all of his $60,000 winnings toward further research so that someday he can actually build the car.
Tovar says, “I want to do all the tests, from materials to a full-sized vehicle. If I make a vehicle that’s 3-D-printed, I want to make sure I feel safe to have my family inside it.”
Another factor worth considering is that 3D printing technology may not quite be ready to build something so large and intricate as Tovar’s WaterBone, or at least not for less than a small fortune. “The cost of producing the first prototype of the rib cage frame has been estimated at $212,047 using current cost of metal and plastic 3-D printing. The cost of a commercial version should be one-tenth of that” , he says. But just as additive manufacturing has caught on like fire with automotive-manufacturers, so has the demand for larger, more precise and less expensive machines in 3D printing and modeling technology.
John Sprovieri, editor-in-chief of Assembly – a magazine for engineers working in manufacturing, says “The automotive industry is trying to reduce the weight of vehicles to meet emission standards. They’re looking for any edge they can get in that regard. They’re finding that the technology can be used to make production-ready parts; parts you can actually use in a product. Right now, the machines for making large-scale auto parts for a reasonable price aren’t available. But that could soon change.”
Tovar is looking to the future when he says, “If we can develop these additive-manufacturing processes on a large scale using multiple materials, we can expand the possibilities of vehicle design and make them both lightweight and safe.” A time when his car and others like it could change the face of automobile design and efficiency.
