Re-Lighting a Minneapolis Landmark

Crane Engineering recently celebrated the restoration of the Minneapolis City Hall/Hennepin County Courthouse Clock — the iconic city landmark was re-lit April 24 following a significant restoration project.

The effort included replacing the white clock faces with glass similar to what was originally in place when the building was constructed. This process included removing the steel framing and replacing it with cast aluminum and removing the neon lighting and replacing it with historically accurate back-lighting.

Crane played a valuable role in the work on the historic downtown icon, which included conducting 3D scanning of the clock. This 3D scanning process involved a scan station that uses a high-speed laser scanner with Light Detection and Ranging technology to collect 50,000 data points per second. These scans — each about 15-minutes-long — were ultimately stitched together to create a “point cloud,” and a digital 3D representation of the clock.

Point clouds can be used to render drawings, models and animations helpful during the engineering and construction process. In the case of the courthouse clock, the scanner made it possible to determine the opening size in the masonry housing of the four original clock faces, and subsequently allowed for the accurate recreation of these faces.

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Beyond the scanning, Crane supported the project’s casting issues when the restoration team wasn’t able to match historic materials to modern day tolerances — specifically, Crane lent a hand to the tightly controlled casting process and the aluminum casting quality standards.

“We were proud to be part of this project and play a role in bringing a historical landmark back to life,” said Tom Crane, P.E., President and CEO.

http://minnesota.cbslocal.com/2017/04/24/mpls-city-hall-clock/