How to Build a Winning Tractor

A tractor is one the most quintessential pieces of machinery on a farm. It’s also one of the most useful tools for teaching engineering, it turns out. Even—or especially—when the tractor is a quarter size. That’s what engineering students from South Dakota State University discovered while participating in the International 1/4 Scale Tractor Student Design Competition.

The American Society of Agricultural and Biological Engineers has held the competition every year for twenty years. Teams are given a 31-horsepower Briggs and Stratton engine and a set of Titan tires. The rest is up to the team. The size is deliberately an awkward one: too large to borrow design elements from garden tractors and too small to look for inspiration in automotive parts and designs.

“The whole idea of the competition is to treat it as if you’re trying to pitch a new product line,” said Ryan VanTassel, a Quarter Scale Tractor Team captain during his senior year. Mid-year the teams have to present their design and cost analysis to a group of industry professionals. Then, in June, they haul their tractors to Peoria, Illinois, where judges evaluate ergonomics, safety, and ingenuity. Finally there’s a maneuverability course, three tractor pulls, and an endurance course where the tractors are driven across bumps and pits. “They do the best they can to try to break your tractor,” said VanTassel.

Needless to say, South Dakota’s tractor didn’t break—the team ended up as the 2018 champs.

What put them at the top? VanTassel attributes the win to a solid team. “It’s a tough competition because you start over from scratch every year, and you don’t always have that continuity from one group of kids to the next,” he said. “We did have team continuity—we had a group that came in as freshmen and stuck with it for four years.” Besides, most of the students on the team have had plenty of hands-on experience—“home grown mechanics,” as VanTassel calls them. “A lot of them grew up on farms and did restoration as a hobby.”

The quarter-scale size forces students to turn to their own ingenuity, rather than off-the-shelf parts. “It’s a gray area where you have to design your own stuff,” said VanTassel. The first year the team entered the contest they hustled about putting parts together. “By the time the next year rolled around we had refined the idea of how we wanted to do things and had progressed from junkyard axles and automotive parts to doing a lot more fundraising and design work.”

This year the competition increased the weight limit for tractors from 800 to 900 pounds. As the South Dakota team had already put in three years making tractors under 800 pounds, they managed to come in 40 pounds under the new limit, while less experienced teams struggled to axe accessories or trim ergonomic elements at the last minute.

In addition to weight and performance, the competition recognizes innovation. The South Dakota team earned additional points with a two-speed power shift auxiliary transmission. “It allowed us to change gear ratios on the fly with the push of a button,” said VanTassel. This was no mean feat for the undergraduates. “Dealing with compound planetary gear sets—you learn about the principles in school, but how to design one? No.” 

Mastering the quarter scale tractor proved to be a full-scale advantage for VanTassel, who now works as a design engineer for Scotchman Industries, Inc. “It is one thing that employers were really pleased to see,” he said. “It definitely made job searching a lot easier, having that on the resume.”
Michael Abrams is a technology writer based in West Field, New Jersey.
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