Broken balance: Unique Balance 29-D-40 for a Bonneville tilt double hung window

Question

My house was built in 2003 and the builder installed Bonneville brand windows and the window balances were manufactured by Unique (both now defunct companies). The concern is the inner sash of a double-hung tilt window.

The left window balance broke. We've always struggled when closing most of our windows in the house. Muscle strength is required as they're difficult to pull down. The balance in question is marked "UNIQUE 29-D-40" and it measures 30" in length. It's a block and tackle system. The cord broke and I'm guessing the spring shot upwards thus creating the hole I know have in the top of the window casing. After removing the balance from the casing I noticed two screw holes where the upper part of the channel was secured to the jamb indicating the installer had an issue when installing the windows.

The pivot shoe appears to still be usable but I couldn't remove it for precise measurements as the channel track has styrofoam glued halfway up - which is where the balance bottom rested and the cord became visible at the bottom of the channel.

Q1. What are the proper replacement parts for this balance? (I know I should buy a pair and replace the unbroken one as well.)

Q2. Is there a better balance system to buy that will fit this window unit?

Q3. Do we need to stick with a 40lb balance set? (how to improve sliding of windows beside cleaning the tracks better)

Measurements:
Sash - app 34"w by 32 1/2" high. weighs 24-25lbs on home scale.

balance - 30" long 9/16" wide 17/32" deep

pivot shoe - approximately 1 1/4" wide, 1 7/16" high in the middle, 1 1/4" high at left and right side, about 1/2" deep

channel track - 1 5/16" wide?, 5/8" deep?

I have additional photos I can provide. Thank you!

User submitted photos of a window balance.

Paul · Accepted Answer

Thanks for posting. I think we can help you replace this balance, but the mechanism you need has to be custom made. We can help you make them, but I will first need to know exactly how many you will need.

I also suggest just replacing the broken balance. I can't believe it, but it appears the Styrofoam is glued to the frame. See if you can replace balance without removing the styrofoam.

To replace the balance, install it at the top and use a pair of needle nose pliers hook the clip to the balance shoe.

As for the stamp, I would custom make it with a stamp option of 30D. Two 30" long balances with this option can hold a sash weighing 24 through 29 pounds. You might also want to try some silicone spray on the track if you haven't already.