Custom Hinges Protect National Treasures is an Open-and Shut Case

The Rotunda of the National Archives Building in Washington, D.C. contains display cases housing the Declaration of Independence, the Constitution, and the Bill of Rights. Flanking these are two sets of seven cases lining the Rotunda’s curved walls that display the “American Originals” document collection. Both banks of cases have seven individual glass lids, each framed in ornate bronze castings.

Custom Hinges

Custom hinges from Weber Knapp make it easier to open and close massive lids on cases protecting the “American Originals” document collection. The collection includes the Gettysburg Address, the voting ledger of the First Constitutional Congress, the Louisiana Purchase agreement, Rosa Parks’ arrest records, and President John F. Kennedy’s Inaugural Address. The case hinges are part of a renovation that should be completed later this year.

The resulting design uses a combined counterbalance/mechanical linkage that fits between the wall and document stands. A special gooseneck arm attaches the hinges to the lid frames. Closed, the lids slope down to 25 degrees and rotate up 60 degrees to their full-open position. The design prompted no major changes to the cases themselves – only a fiber optic light bar needed a slight redesign to accommodate pivoting motion of the arm. NARA says hinges must last a minimum of 10,000 cycles. Weber Knapp, has successfully tested the hinge to 36,500 open/close cycles.

Lawrence Kren from Machine Design
September 1, 2005