New balances for a wood double hung window

A quick learner says:
I have two wood double hung windows that require new balances. The bottom sash in each is 24-5/8" wide X 21-1/16" high, 1-1/4" thick, weighs 6 lbs. and has 5/8" X 5/8" dadoes along each side for the previously used spiral type balances (these balances were lost during demo so we have to start from scratch). The top sash is the same except that it is 20-9/16" high. The assembled window height is 40-5/8"

From your web site it looks like a series 500, 5/8" diameter balance would do the job but I need your help in determining the strength and length. Also, what hardware would be required. Previous attachment appears to have used a bracket similar to a #17-007 which mounts to the horizontal surface of the sash.

Attached are some pics of one of these windows. I need to build new frames for them so I need to know if these new balances affect the design of these frames.

Sincerely, Ray
User submitted photos of a window.
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Paul from SWISCO responded:
Good afternoon, Ray. Thanks for contacting us.

Without a balance on hand, it would be very hard for us to identify anything for certain. That said, we may be able to take a guess. Before I can, though, can you tell me the glass height for both the bottom and top sash?

Like I said, with that information the best I can do is guess, but it's at least a step in the right direction.
A quick learner from Cape Elizabeth, ME says:
Hi Paul
The glass panes in all sashes are 18" in height.
Hope this helps.
Thanks, Ray
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Paul from SWISCO responded:
Great, thanks Ray. Now, again, I just want to stress that I don't know if these balances will work for you. That said, check out our S500-19 for the top sash and our S500-21 for the bottom sash and see if you can get these to work. Like you said, you'll also need a bracket similar to our 17-007.
A quick learner from Cape Elizabeth, ME says:
Finally finished stripping, reglazing and painting the sashes and building the new frames for these two windows (see attached). I plan on ordering four(4)S-500-19 and four(4)S500-21 balances as you suggested with the red tip (sashes weigh about 4# each), eight 17-007 bottom brackets and one (1) 75-005 charging tool. What do I need for screws for the bottom brackets and fasteners for the top of the balance where it attaches to the window frame?

Please comment-Thanks, Ray
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Paul from SWISCO responded:
To install the balance tube to the window frame, use our 33-017 #8 X 1" SS pan head screw. For the 17-007 metal bracket, use our #33-090 #8 X 3/4" SS pan head screw. You might already have these screws in your shop.
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