Body-shaped for supermileage

  • 07-Jul-2010 12:24 EDT

Cedarville University's car makes the required stop at the tilt table. The table replicates the 20° bank of the Eaton test track.

Six different single-occupant vehicles designed and built by teams of collegiate engineering students snared four-digit fuel economy at Eaton' Corp.'s Marshall, MI, test track during the 31st annual SAE Supermileage competition on June 10-11.

Universite Laval of Quebec, Canada, took top honors for the third year in a row by recording 2340 mpg. As required by rules, vehicles must maintain a minimum average speed of 15 mph and a maximum average speed of 25 mph over six laps on the 1.6-mi (2.6-km) track.

The challenge requires that each vehicle use a Briggs & Stratton single-cylinder four-cycle engine although teams can modify the engine.

Body shape is at each team's discretion as there are no restrictions on a vehicle's height, length, or width. Rules require all vehicles to have at least three wheels.

"Although some teams still use a low-to-the-ground, torpedo-type body shape design, what's real interesting to me is more vehicles in the competition are letting the air flow underneath the vehicle," said Jim Gluys, Principal Engineer for Commercial Vehicle Transmissions at Eaton Corp. and Event Organizer of SAE Supermileage 2010.

Binghamton University's new for 2010 vehicle had an 18-in rear wheel and two 24-in front wheels that were 14 in from a body that was 14 in from the ground. The body's front end was formed from positioning poplar wood strips around a NACA 64 airfoil structure, but the vehicle's back end was shaped differently to accommodate the engine bay.

"Because we didn't have the funding or the time to go to a wind tunnel, we taped about 500 four-inch-long strings to the body and placed a giant fan in front of the car to see how those strings moved as air flowed over the body," said Robert Roecklein, the New York school's aerodynamics leader.

While Binghamton's team used a tufting process as a wind tunnel substitute, the Polytechnic Institute of New York University team used the school's wind tunnel to test a 1/20th scale model of their 114-in- (2896-mm)-long vehicle that made its SAE Supermileage debut.

"We used a Dimension 3-D printer to make the scale model from ABS plastic. The model was tested as drawn in CAD. We then measured the wind tunnel data and compared it to our CFD analysis, which we did in Dassault Systèmes' SolidWorks CosmosFloWorks and Ansys Fluent. After verifying that our analysis converged, we kept using CosmosFloWorks for further analysis as the body shape evolved," said team captain Yuri Shnirman.

The senior design project had a $1500 budget, so manufacturing considerations greatly influenced the vehicle development process for the NYU-Poly team.

"The original frame had several supports. But we basically asked, 'What supports are unnecessary?' and took those supports out of the design to save weight and money. A mono-film canopy connects to the body by magnets, and that canopy has abrupt edges," said frame leader Jake Nalos, adding, "We wanted a more streamlined vehicle, but because of manufacturing requirements that wasn't possible."

The Penn State University-Behrend College team returned to SAE Supermileage with the same vehicle body that competed at the 2003 and 2009 events. "We started working on a brand new body and brand new frame, but about a month and a half before the competition we decided not to rush things and risk messing something up on it," said team captain Mike Roseborough.

Both the 2010 car and the under-development vehicle have a low ground clearance. "This year's car has a teardrop-shaped body, but the best way to describe the other car is it's kind of shaped like a sneaker, a running shoe. If the new car gets used at next year's competition, it will be about a third of the weight of this year's model, which weighs around 150 pounds," Roseborough said.

This year's top 10 finishers for highest mpg were the Universite Laval (2340 mpg), University of Ottawa (1486 mpg), Northern Illinois University (1265 mpg), Rose-Hulman Institute of Technology (1262 mpg), Cedarville University (1180 mpg), Ecole de Technologie Superieure of Quebec, Canada (1044), University of Akron (844 mpg), University of Massachusetts-Amherst (828 mpg), Binghamton University (792 mpg), and PSU-Behrend College (777 mpg).

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