How Penn engineers are restoring historic Springfield Mills
The gristmill on Wissahickon Creek, which dates back to 1761, required repairs to its modern machinery upgrades. Volunteers at the Morris Arboretum & Gardens turned to MEAM’s Precision Manufacturing Lab at Penn Engineering for the design of precision components.
Jason Pastor (left) is a senior coordinator of instructional labs at the Department of Mechanical Engineering and Applied Mechanics (MEAM) at Penn Engineering.
(Image: Courtesy of Penn Engineering)
Dating back to 1761, the mill sits on the Wissahickon Creek—which originally powered the mill by water—and offers the most complete inventory of original gristmill works and related machinery in the area, with only four remaining mills in the Wissahickon.
In the early 2000s, the Run-of-the-Mill volunteers—a dedicated group including engineers and employees of the Morris—worked to restore the mill back to functionality.
The mill had relied on a 5-horsepower electric motor added approximately 20 years ago, which drove the machinery through a belt-drive system. This approach caused significant wear on the mill’s wooden components, particularly the lignum vitae bearings—a super-dense wood used in the original construction. Two years ago, the volunteers noticed the belt shuddering and jumping and deemed it unsafe to run.
Bryan Thompson-Nowak, director of education at the Morris, contacted two technical staff in MEAM: Jason Pastor, senior coordinator of instructional labs, and Ari Bortman, educational laboratory coordinator.
Before the belt system was added, the mill ran using the great gear, a 6-foot diameter, 1-foot thick wooden gear that powers the smaller gears throughout the building. “One of the volunteers, Ted Bell, suggested we move the power back to the great gear,” says Pastor. To do this, Pastor and Bortman manufactured a two-foot diameter sprocket and chain, which will eliminate load on the auxiliary shaft that the rubber belt had driven. “The great gear is so wide because that gives it a big lever,” Pastor explains. “It doesn’t have to be super strong to turn these smaller gears because it has a big mechanical advantage.”
This approach offers several benefits, says Bortman; “We don’t need to put in a new motor or electrically rewire everything. This would require less tension to prevent slipping and would allow us to use the motor and gearbox already in place in the mill.”
This story is by Claire Sibley for the Morris Arborteum & Garden’s Seasons Spring/Summer 2025 magazine. Read more at Penn Engineering.
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