Question about Spring lengths in Block and Tackle Channel Balance

I need two block and Tackle balances with standard bottom and top pieces without wings for a non-tilt sash window. Picture 6941 above shows a complete balance taken out of the window and underneath it is the spring that came out of the other balance when the cord broke. (The other pictures are to show you the ends and the spring clip on the complete balancer) The metal parts of the two balancers measure the same length, namely 42 inches. The back on both measures 9/16" and each is 5/8" high. 

However, the springs in the two balancers are not the same length. I think that is why I have been having problems. The spring inside the complete balancer in picture 6941 measures 27 inches long. The spring alone that came out of the other balancer measures 23 1/2 inches long. Note too that the 27 inch long Spring inside the balancer looks heavier and stronger than the spring alone. I think the complete balancer above with the 27 inch spring may be the original one for the window which was put in in 1977. 

The balancer on the other side of the window has been replaced twice, as far as I remember. Now that I see the springs are different that would seem to explain why the window has not worked correctly, even after new balancers were put in. The last was put in about 2018 0r 2019. (The company which put the window in in 1977 and replaced the balancers several time but may have used the wrong replacement part, is no longer in business.) 

Even when the balancer was replaced in the past, I had a very hard time raising the window and especially lowering it. I had to hang on it to lower it. When the cord on the replacement balancer with the shorter spring broke, I got my son to remove the window and took out both balancers so I could compare them and know what to order. Am I correct that the different lengths of the Spring would make the difference in the way the window worked? 

The full balancer in the picture above, which may be from 1977, has the number 4150A on it. The other balancer that broke has the number 41 DS 43 on it. That seems to indicate that they are made for different weights. I think I need the 4150. The window weighs 45 pounds or maybe even a little more if my scale was wrong. One silver take out clip broke when the window was removed. The other could not be opened. Thus, I will also need new silver take out clips. They can be replaced, can't they?

Dear Casey,

Sorry not to have gotten back to you right away.

Bottom attachment:

As you asked, I measured the bottom attachment to see if I need the S351 or the S390 balancer. Actually the measurement seems to be between the two you gave me. It seems to measure 1 1/16 inch. Also it looks a little different than the one in your picture. I have attached pictures. Since my reading on balancers has taught me that you drop one inch in actual measurement for the length of the balance (i.e. a 42 inch long balancer is given the number 41 for length) and since drop the extra 1/16 inch for width (i.e. a 9/16 in wide balancer is known in the trade as 1/2 inch balancer), I am wondering whether the extra 1/16 that I see on the bottom attachment gets dropped and you call it a 1 inch attachment.

Weight of the window:

Concerning the weight of the window, my grandsons carried it into the bathroom when they removed it, and put it on a bathroom digital scale holding it upright lightly with one finger. The scale registered 45 pounds. The number I gave you on the older balancer I took out, which may be the original, says 4150. From what I have read, that means it is a 42 inch balancer (just measuring the metal part) and it is for a 50 pound window. Would a balancer for a 50 pound window be better than having a balancer for a 45 pound window? I do not want to go below 45 pounds. I think that has been the problem with the replacement balancer I had in my window that did not work correctly and which eventually broke. That was the one numbered 41DS 43. You said it was peculiar that my balancers had different number codes. I think you should go with the one that said - a 4150A. (I missed the small "a" ahead of the number 4150 when I sent it to you in the previous e-mail. Maybe that tells you something). These numbers are etched on the metal, not simply stamped. The window is big and it is heavy. It measures 43 1/2 in high by 42 5/8 wide. I don't think it is vinyl. It is white but feels like strong metal. I think the windows are thermal glass. At another site on the Internet (not Swisco), they talked about 300 series Caldwell balancers and 400 series Amesbury balancers. The 400 series was for balancers that had the number etched rather than stamped and also would be for the weight I need. Do you have those two kinds of balancers? When you sent the picture of the bottom attachment, those two pictures were numbered in the 300's. Do you have balancers numbered in the 400's?

Regarding the take out clip, the number 16-002 appears to have the same measurments as mine. I will get 5 of those - just to have extra.

In summary, I would like to get two (2) block and tackle balancers for a non-tilt window. The balancers should be 42 inches long (measuring just the metal part), 5/8 in. high, and 9/16 in. wide. They should support at least 45 pounds. The bottom attachment should be 1 1/16 inch (which may be 1 inch in the trade). I would also like 5 (or 6 if they come in a package) take-out clips # 16-002.

How much would this be with shipping?

Thank you.