Inverted block and tackle balances are designed for tilt windows. These balances are "inverted", meaning the spring is located at the bottom of the balance and the rope and pulley are located at the top. These balances work in tandem with a T-lock shoe to allow your window to tilt in, similar to a standard pivot lock shoe. However, the T-lock shoe is attached directly to the balance. We have a few different styles of inverted block and tackle balances and all function similarly. Continue reading to learn more about inverted block and tackle balance and how to find the correct replacement.
The easiest way to determine what series balance you have is to look at the bottom of the balance and the T-lock shoe.
Our 716 Series has a square metal channel at the bottom and the T-lock shoe is perfectly vertical. For our 747 Series, the base of the metal channel is slightly curved inwards and the T-lock shoe is curved slightly forward to accommodate for this.
Pictured above are the differences in the metal channel. The 747 Series (right) has an indentation on the lower part of the metal channel, the 716 Series (left) does not
Here you can see the differences in the T-lock shoes. Note how the 747 Series (right) is slightly curved forward whereas the 716 Series (left) is perfectly straight
Another series inverted block and tackle balance we offer is our 316 Series. This series looks quite a bit different from the 716 and 747 Series balances, but it functions exactly the same.
Pictured above is our 316 Series T-Lock shoe and the bottom of the balance.
Here is the T-Lock shoe removed. Note how there is an additional plastic part attached to the base of the balance
All three series side-by-side (from left to right: 316, 716, 747)
Replacement Inverted Block & Tackle Balances
To find the correct replacement balances, you will need to know which series balance you have and the stamp on the balance. The stamp will often be something like "22 2" or "22B".
If your T-Lock shoe is damaged, you will need to measure the width and thickness of the shoe. After that, you will need to look at the color of the "puck" on the back of the shoe. This can either be white, green, red, black, blue or metal. Next, determine if your cam is open or closed. In the picture above, the 716 (middle) has a closed cam, the 747 (right) has an open cam.
If your balance does not have a stamp, you will need to measure the length of the metal channel and weigh your sash.
One type of balance that is closely related to inverted block and tackle balances are crossbow balances. These balances are no longer available and are replaced with an inverted block and tackle balance.
Here you can see an example of a crossbow balance given to us by a customer.
To be converted out of a crossbow balance and into an inverted block and tackle balance we need the following information:
1) The whole sash height
2) The glass height
3) The weight of your sash. To get an accurate weight you will need to remove the sash and weigh it using a bathroom scale or something similar.
4) The width of the plastic T shaped piece. It'll either be 15/16" or 1-1/4". This shoe can be various colors such as black, blue, and red.
If you have questions about how to replace your current window balance system or questions about window balances in general, contact us, chat with us, or give us a call at 1-800-842-0974 and we'll be happy to assist you.