Unique Window Balances

A quick learner from Danvers says:
I need some window balances for a unique window.

The round top is 21" up the side and weight is 20lbs. The square sash is 31" and weight is 22lbs.

The window was built to match an existing one that was thrown away before I was able to see. We have 600 series spiral balances on some of the older windows I recently tuned up.
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Paul from SWISCO responded:

Perhaps I can be of assistance. First, the curve top wood sash. If I understand correctly, the curve starts at 21". If that's right, then you can use S500-20 blue tip balance. For the 31" high rectangle sash, use S500-30" blue tip balance. The bottom sash bracket will be our 17-012. Below is a generic directions on installation:

To install these balances, you would drop them from the top on the side of the sash. Use the 33-017 screw to attach the balance tubes at the top. Now raise the sash and have someone hold it up while you attach the bottom bracket 17-012 with the 33-090 screw while the U-shape opening of 17-012 corrals the spiral. With your finger bring up the spiral to the bracket and attach the 75-005 tool and turn the spiral clockwise three turns and hook it to the fork of the bracket. Repeat the other side and try the sash. If sash creeps down, raise and hold up the sash and give the balances another turn or two.

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