On June 7 and 8, the streamlined, three-wheel car built by the UMass Amherst Supermileage Vehicle (SMV) Team, which calls itself Zoom Mass, rolled smoothly through the Society of Automotive Engineers (SAE) Supermileage® competition in Marshall, Michigan with a car shell made of shrink wrap and an emergency engine getting a tightfisted 843 mpg and running mainly on true grit, improvisation, and elbow grease. “As usual, we ran into a number of technical difficulties, which included killing an engine, two batteries, and a starter motor,” says SMV faculty advisor Jonathan Rothstein of the Mechanical and Industrial Engineering Department, “but we persevered!”
The team’s perseverance landed Zoom Mass in fifth place among 30 collegiate teams, representing schools from Canada, Mexico, Pakistan, and the United States. But it wasn’t easy!
No one from the SMV team could have predicted such a grand finale just 15 hours before the competition began, when the whole UMass contingent was gathered in the parking lot of its hotel, feverishly cannibalizing two broken engines to create one that worked.
Here’s the backstory. During the fall 2011 semester, the SMV team began with the standard, three-horsepower, 115-cubic-centimeter, Briggs and Stratton, lawnmower “starter engine” supplied by the SAE to each college in the competition. For the next few months, team members heavily modified that engine, “souping it down” as it were, to 50 cc and adding a Honda scooter overhead valve and piston system. But then, on the eve of the competition, Murphy’s Law set in with a vengeance.
“It turns out the sleeve we inserted wasn’t fitted properly,” explains Rothstein, “so during a test run in Marshall, it popped out of the engine and into the crankcase.”
The good news was that the team had brought along a backup engine. The bad news was that the backup had also failed, back in Amherst just before the competition, during another test run. So the only alternative was what really good engineers do best. To adlib.
“The kids were great,” says Rothstein. “They pulled the engine out of the car. They had to take the head off one engine and stick it on the other. Then they had to glue the new head gasket in place, which requires 24 hours to dry, but they only had 15 hours before the competition next day. So there was a lot of crossing of fingers.”
Though the “crossing of fingers” is not found in any engineering textbook, it evidently did the trick. Next day, driver and chief mechanic Jack Washington cruised around the 10-mile course with ease. He did that for six runs, in fact. The proof was in the putting down of the gas pedal. It was also part of a steep, year-long, learning curve.
“The good results we got in this year’s competition really came out of what didn’t work last year,” notes Rothstein about building the team’s cost-efficient car from the ground up. “Last year we had a fiberglass shell, but this year we decided it took too long, and it was too much work, and the fiberglass was not designed to be adaptable. So this year, instead, we decided to make our shell out of the same shrink-wrap plastic used to winterize vessels in boatyards.”
The SMV team built an ultra-light aluminum frame and then set up fiberglass rods to contour the shape of the shell, almost like building the ribs of a model airplane fuselage. Then team members fitted shrink wrap, donated by a local boatyard, around the rods and heated the plastic to make it snug and tight.
And Bingo! They had the amazing shrinkable car. It was like wrapping a big birthday present or a sprained ankle.
There were many other issues with last year’s car to learn from, including too much friction.
“Last year the back brakes were actually rubbing,” explains Rothstein about the 2011 competition model. “We had also attempted to use a three-speed internal gearing system in the back wheel, and it turns out that system had a lot of friction. You lose a lot of energy that way.”
The solution this year was a one-gear system, which can actually be disengaged from the back wheel so it can coast free of the engine. This adaptation plays into what was literally a “revolutionary” innovation created more than a decade ago by a team from UMass Amherst, a driving technique first performed during the SMV competition in the 1990s by faculty advisor Ian Grosse’s team.
As Rothstein describes this technique, “So the way we drive the car is to get it up to about 25 mph and then let it coast. We keep doing this off and on for the whole run. All the teams do it now. And with this one-gear system, we could disengage the engine from the back wheel and let the car coast on some really nice bearings. I believe the way to get really high mileage in this competition is to have a car that rolls very well.”
One result was that Team Zoom Mass also disengaged Murphy’s Law. Last year, everything that could go wrong did. This year, everything that could go wrong was put right. This is the primary reason why Rothstein declared that “I’m extremely proud of them all,” meaning the 20 members of his hard-working and fast-thinking team.
Rothstein was also very grateful to the major sponsors that made building the SMV possible this year, including Sensata Technologies, Kollmorgen, and the Scuderi Group, LLC, which donated about $5,000 apiece, along with some key software donated by Solidworks. It was a team effort in every way. (June 2012)