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Constant Force Balances for "stay put" Operation

Until they malfunction, Balances are an element of windows often taken for granted. There are a wide variety of balancing methods currently in use but the most popular among the highest quality window manufacturers is the “Constant Force Balance” (CFB) system.

Other methods such as string and tackle, coil spring, tubular spiral and rope and pulley (traditional) are often fine for a time, however, eventually they all fail in some way or another. Some get out of adjustment, others have moving parts that can break or malfunction, and others have ropes or strings that can break.

We choose to use the CFB system because of their simplicity. And they work well forever. The CFB has no moving parts! It consists of a 1/2″ wide stainless-steel band that is formed into a coil with a specific tension. One end is attached to the jamb and the other to the sash. The sash is then permanently hung with a resistance precisely tuned to its weight. The result? The sash stays in place. Whether you raise it 2″ or 20″, it will stay put.

The plastic housing in the picture above is mounted into a mortise cut into the jamb side, just below the meeting rail of the lower sash. The “ells” on the housing protrude jamb opening and the sash just “sits” on the “ells” which are then screwed into the bottom of the sash.  Once that is accomplished the sash is then “hanging” by the calibrated coil springs.

27 lb spring for 54 lb sash. Most are only one or two units, not three.
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