Unsure of Series 170 & 171 Coil Balance stamp number for replacement

Question

Hello,

As you can see in the last picture of my double hung window coil balance, the pivot lock shoe has retracted back to the coil balance and even when turning the metal cam to slide the shoe down the track it retracts right back up.

I originally began this project with the thought that I only had to replace the previously broken pivot shoe on each side, which I did using 15-192 and substituting my old metal cam since it had a larger slot compared to the 15-192 metal cam with a smaller slot however I then realized that the shoe still won't release tension and stay slid down if I manually push it down. I was thinking I may need to replace the coil balance part and I've searched on the site for replacement pieces and other FAQs and it seems I need both a Series 170 and 171 along with the related cover and drum.

I was going to purchase these items but I cannot determine what stamp number is on my current (original) coil balance as I do not see any markings when I take it apart and try to unroll the coil. Given that the Series 171 only has 405/406/407 I'm guessing the 170 will also be one of these numbers but I'm unsure of the differences. Are you able to determine which stamp number I should be required to purchase?Thank you for the help.

Tom · Accepted Answer

Hello! Thanks for reaching out to us. I'm glad you weighed your sash; that makes this very simple. The rule of thumb for coil balances is to divide the sash weight by the number of springs that support it and then pick accordingly. In your case, 22 divided by 4 ends up being 5.5.

Now, here's where it gets a little tricky. There is no Series 170 or Series 171 spring that can hold 5.5 pounds, so we have to get creative. What you can do is use one 5 pound spring and one 6 pound spring on each side, which adds up to a total of 22 pounds of support.

So my official recommendation would be the S170-405 (5 pounds each) and S171-406 (6 pounds each). As long as both sides are identical then you should be good to go!

Please also note that the front bumps on the 15-192 may need to be shaved down for this shoe to slide comfortably in the track. Your window is the old Simonton brand and I've been told that the bumps on the 15-192 get in the way of operation. You'd have to snip them off or grind them down.