Curtains shall be pattern BG-6 composed of 5/16″ galvanized rods and ¾” X 1/8″ aluminum (6063) vertical links presenting and alternating rectangular pattern. Horizontal rods shall be overlayed with 3/8″ O.D. PVC tubes, (3/8″ x .022 aluminum 3003 optional). Horizontal rods shall be 2-1/4″ on center, (1-3/4″ optional). Vertical links shall be 6″ on center. Or curtain shall be pattern SG-9 composed of 5/16″ galvanized rods and ¾” x 1/8″ aluminum (6063) vertical links presenting a continuous rectangular pattern. Horizontal rods shall be overlayed with 3/8″ PVC tubes, (3/8″ x .022 aluminum 3003 optional). Horizontal rods shall be 2-1/4″ on center, (1-3/4″ optional). Vertical links shall be 9″ on center.
Guides are to be of extruded aluminum with double wool piling to contact both faces of grille, acting as wearing surfaces and sound deadener.
Counterbalance Assembly shall be furnished with oil tempered helical torsion springs having a 25% safety factor. Springs to be fixed to tapered cast anchors, permanently lubricated, mounted on a single solid torsion rod. Torsion rod to be attached to spring tension adjustment wheel. Assembly to be housed in steel pipe shaft of adequate diameter, deflection not to exceed .03″ per foot of span.
Bracket Plates are to be of steel plate. Sealed ball bearings to support the counter balance assembly. Brackets to form and closures and support hood.
Operation is to be (manual, with a lift handles) (by chain and gear galvanized chain with maximum pull of 35 lbs.) (by motor operator).
Locking of manual operated grilles to be by means of slide bolt locking device operable from inside or outside. Chain lock keeper on chain operated doors. Motor operated grilles to include self-locking gearing plus chain locking device for emergency chain.
Finish for aluminum tubes is to be (mill) clear anodized 204R1) (Duranodic # ). Steel surfaces to be painted one shop coat of rust inhibiting primer. PVC tubes specify color Bronze, Silver or Gold