Bi-Fold Door Construction - This horizontal Bi-Fold design is constructed of heavy aluminum structural tubing, welded into a strong framework, and fitted with 2" thick, mineral wool insulation. The door panels are covered with the same 0.040" aluminum as with the side-wall and roof panels, smooth on the inside. The main door hinges are constructed of 1/2" thick x 2" wide aluminum bars, welded to the doorframe and pinned through two other bars on the adjoining members with 3/4" diameter, stainless steel pins. There are at least four sets of these at both the top of the door and at the center hinge point. The door utilizes a rubber, tadpole-type bulb gasket at the pinch points at the top and center hinge, with a soft, double bulb silicone rubber seal on each side. Once in place, the door is clamped shut by threaded rod with a handled nut and screwed down tight, providing the best door seal available. A 2 hp brake motor, directly connected to a 60:1 reducer drive, which in turn is directly connected to a winch, raises the door. When activated, the door is opened in less than 45 seconds, utilizing four (4) 1/4" diameter stainless steel aircraft cables (each is rated at 6,400 lb. cap.). For safety, the door is designed so that any one of these four cables can support the entire door.
