On Wednesday, April 27, supporters of the University of Massachusetts Amherst Supermileage Team – Team ZoomMass for short – gathered at Western New England College (WNEC) in Springfield for a demonstration, rally, presentation, and celebration. The star attraction was an eight-and-a-half-foot-long, 100-pound, teardrop-shaped, neon-green vehicle designed to get as much as 1,500 miles per gallon of gas at the Society of Automotive Engineers (SAE) national supermileage competition in Marshall, Michigan, in early June. The 6:00 dinner was followed at 7:00 by presentations given by the team’s faculty advisor, Dr. Jonathan Rothstein of the UMass Amherst Mechanical and Industrial Engineering Department, and others. The event was also covered on WGGB-TV 40.
UMass Amherst has placed in the top three several times at the highly competitive SAE competition and created at least one lasting innovation, our method of cutting the engine and coasting for large segments of each run on the test track. “One of the things we do to optimize the mileage is to drive the car till we get up to about 40 mph,” says Dr. Rothstein. “Then we turn the engine off and let it coast until we get back down to five mph. Then we turn the engine back on. That allows us to maintain the engine at its most efficient.”
Starting last September, Team ZoomMass began designing and building the vehicle from the ground up, starting with the standard, three-horsepower, 115-cubic-centimeter Briggs and Stratton lawnmower “starter engine” supplied by the SAE to every team in its competition. Actually, Team ZoomMass has been scaling down and modifying three starter engines to see which is the most efficient. They’ve created a 50 cubic centimeter fuel-injection engine, a 50 cubic centimeter carbureted engine, and a 25 cubic centimeter carbureted engine.
Depending on which engine tests out with the best fuel economy before the competition in June, they can pop it right into the 85-pound chassis and enclose the driver in a removable 15-pound, fiberglass shell with its clear-plastic bubble. Then the little car is ready to rumble.
The team is also experimenting with two different transmissions. One is called a NuVinci continuously variable transmission. The name pays homage to Leonardo da Vinci, the first person to create the concept of a continuously variable transmission, which allows the drive shaft to maintain its most efficient rpm setting indefinitely.
“The other transmission is a variable-ratio transmission like the derailleur and sprockets you have on a bike,” explains Rothstein. “The real question for the bike transmission is can it handle the power being outputted by the engine.”
The year-long process of designing, building, assembling, and testing the supermileage vehicle puts much of the UMass mechanical engineering curriculum to work. The students use computer modeling software to design the car, they do fluid mechanical modeling to optimize the aerodynamics, they create three-dimensional CAD drawings of all the parts, and they use a special software to design the fiberglass shell.
They’ve even written a special mathematical code that takes into account the drag coefficient of the car, the rolling resistance of the bearings, the weight of the vehicle, the efficiency of the engine, and other factors to predict the ultimate mpg they will achieve.
“It’s a great culminating experience for our seniors because they take a lot of the principles that they’ve been learning in the classroom and they apply them to a year-long project,” says Dr. Rothstein. “The project depends on a very big design component, fluid dynamics, making composite materials, teamwork, project management, time management, and much more.” (April 2011)