Apr. 27, 2015 | By Lilian
Local Motors, in partnership with the Advanced Research Projects Agency-Energy (ARPA-E), announced the winner of the LIghtweighting Technologies Enabling Comprehensive Automotive Redesign (LITECAR) Challenge. The design challenge served to accelerate innovative ideas by using novel material technologies, structural designs, energy absorbing materials and unique methods of manufacturing to reduce vehicle curb weight while maintaining current US automotive safety standards. More than 250 conceptual designs were submitted.
The winning design, Aerodynamic Water Droplet with Strong Lightweight Bone Structure ("WaterBone"), was created by Andres Tovar, a mechanical engineering assistant professor at the School of Engineering and Technology at Indiana University-Purdue University Indianapolis, and his group of graduate students.
Tovar's proposed winning vehicle design which uses of multi-materials, and the 3D printing manufacturing process, has the shape of a water droplet with an embedded ribcage-like structure called a spaceframe. The water droplet shape provides a low drag coefficient for higher fuel economy, while the ribcage is designed with a graded porous structure, similar to the ones in bones. These structures provide the mechanical strength required for the structural stability and drivability as well as the energy absorption capabilities for the occupant safety in the event of a collision.
The envelope's material is a polymer composite, which provides desirable characteristics of a monocoque design. The spaceframe's material is functionally graded aluminum alloy foam. The layout of the proposed spaceframe is designed using a specialized and unique topology optimization algorithm for crashworthiness. The monocoque-spaceframe design is built using additive manufacturing (3D printing) technology.
The proposed design has the following differences from the current state-of-the-art in vehicle design:
Novel multiscale structural layout.
At the vehicle scale, the generated spaceframe has a structure similar to the one of long bone. In essence, the aerodynamic water droplet shape is protected by specialized ribcage that follows principles of Michell-type frame structures. At the component scale, each spaceframe tubular component is filled with a functionally graded cellular structure. Such complex, lightweight, multiscale structural layout is manufacturable using 3D printing technologies.
Novel lightweight multi-material design.
The envelope's polymer composite provides desirable safety characteristics of a monocoque design traditionally found in Formula 1 cars and aircrafts. The metallic (functionally graded cellular) spaceframe provides a level of protection similar to racercars that also use spaceframe design. However, the proposed design has less than 50% its weight with significantly lower part count. The result is a design of very light, strong, and safe (crashworthy) components with the possibility of utilizing a wide variety of plastics and metals.
Novel manufacturing process.
The freedom in the multi-scale/multimaterial design is possible due to the benefits of 3D printing. Besides providing lightweight and innovative vehicle designs, 3D holds the promise of cleaner and environmentally friendlier operation that allows complex part production with minimal overall material wastage. It also allows free-form mass customization with reduced time to market and low overall cost.
Tovar will receive the $60,000 grand prize for his pioneering vehicle design concept. The remaining $90,000 in prize money will be divided between five additional submissions that were recognized for their ideas by both the Local Motors' online community and LITECAR judging panel.
- First runner up ($40,000): Sumit Lakhera and Feyzi Aras, Skeletos
- Second runner up ($20,000): Wilburn Whittington, David Francis and Kyle Johnson, Metal Matrix Metallic Composites
- Innovative design component ($10,000): Yuqing Zhou, Kazuhiro Saitou and Jeff Xu, Manta
- Innovative safety component ($10,000): Alexander Rivera, Modular Sprung Pod Car
- Community favorite ($10,000): Anthony Kim and Sheetanshu Tyagi, Apalis
"LITECAR has been critically important to Local Motors because it has stretched the boundaries of the world's largest open-hardware innovation community to include a focus on the subject of weight reduction," said Co-Founder & CEO of Local Motors, John B. Rogers Jr. "For ARPA-E, this is a highly conceptual challenge bringing in system-level thought from around the world to focus on a next generation problem. Having the tools to achieve this thought and work is a critical enabler for such an agency."
The LITECAR Challenge launched on 2 January and voting concluded on 20 March. The submissions were evaluated on four main criteria: vehicle curb weight reduction, vehicle safety, innovation and supporting evidence.
Posted in 3D Design
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I concur with Jason's comment - the surface tension brings the water droplet into a spherical shape while in free fall. The characteristic "pointy" end is the result of the droplet dangling prior to falling, and quickly shrinks away as a result of surface tension. Large drops actually become unstable during free fall, concave due to their larger frontal surface area, and split into smaller spherical droplets. Cars designed specially to minimize their overall drag coefficients look substantially different than a water droplet.
Jason wrote at 4/29/2015 8:24:54 AM:
Water droplets are not an aerodynamic shape. The shape is a result of surface tension as the drop releases from what it is clinging to. Real airfoils for low drag have their max width around 2/3 back from the tip. Rain drops don't even fall in this shape WTF.
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