Enron Field, the new baseball stadium in Houston, Texas, features a retractable roof and a natural grass playing field. A unique suspension system reportedly enables the roof to operate flawlessly.
The roof travel mechanism was designed by Uni-Systems Inc., Minneapolis, Minn. It features independent suspensions for each of the 142 wheels that carry the three huge roof sections. The suspension springs compress a small amount when the wheel meets a high spot on the rail. Uni-Systems didn’t think that metal springs would be able to meet the 25 year working life criterion, so a system based on a urethane elastomer was chosen.
Development work was conducted by Uni-Systems and Kastalon Polyurethane Products, Alsip, Ill. Kastalon already was involved in the project in designing a bumper stop assembly for the roof system. The team selected Adiprene urethane prepolymers from Uniroyal Chemical, a Crompton business, Middlebury, Conn.
The patented cylindrical springs consist of alternating layers of steel and urethane around a central shaft. The laminated assemblies are only 20 cm (8 in.) in diameter and 23 cm (9 in.) tall, yet they support a normal load of 555 kN (125,000 lbf), with peaks to 1.4 MN (325,000 lbf).Other applications: Adiprene urethane also is used in the stadium’s roof tie-down system. Despite its great weight, the roof must still be tied down during high wind or hurricane conditions. Use of urethane enables the tie-down springs to maintain constant tension during the lift/drop cycles experienced during high winds.
For more information about urethane applications, contact Bruce DeMent, Kastalon Inc.; tel: 708-389- 2210; fax: 708-389-0432; Web: www.kastalon.com.
