Miller Park Retractable Roof Braking System

Milwaukee’s one-of-a-kind ballpark features traditional architecture with a unique fan-shaped retractable roof. The 25-million pound, seven-panel design opens and closes in approximately 10 minutes. Each moveable panel is supported at its pivot end behind home plate and at its running end beyond the outfield. 10 bogies (referred to as end trucks in the crane industry because they consist of the truck frame, wheels, bearings, and axles that support the bridge girders) open and close the roof. These bogies run on a curved rail system. Although Miller Park’s retractable roof is unique and provides protection from the elements, it has required design changes to improve performance.

In 2003, the retractable roof at Miller Park required improvements at the running end of each of the moveable panels. The Southeast Wisconsin Professional Baseball Park District, part owners of Miller Park, hired the engineering firm Hardesty & Hanover, LLP, of New York to analyze the situation and provide a recommendation.

After extensive evaluation, Hardesty & Hanover (H&H) recommended a redesign to the bogie system to improve performance. All 10 of the existing two-wheel bogies would be replaced with four-wheel bogies containing the drive train assembly. The drive train consisted of a new motor, brakes, and gear box assembly. The new bogie would now allow the weight of the load, the roof panels, to be equally distributed over four wheels versus the original two wheels—all within the height, width, and length restrictions defined by the existing structure.