Sash window won't stay up UPDATE

[Sylvain VAN DER WALDE]

Hello all.

I've had very little energy for the past few weeks; but today I felt better and got "stuck in" that window job. Findings: the weights are the correct ones, and are attached to the sash cords. I'm able to raise the window to its full extent. But (a big but?), with the window raised to its full extent, the bottom of each weight is 8 inches approx. from the bottom of the weights' housing. Now, I know a _little_about the law of levers (leverage/s?), and a possible solution comes to mind. Does the distance between the pulley centre and the weight attachment affect the force pulling on the window? And if so; if I increase the length of the sash cord (or re-position it if it's wrongly attached) so that the weight is just clear off the bottom (which I intend to do anyway) will that make a difference? As a matter of interest; the sash cord is not visible with the hatch open, so I'm unable to add some weight as has been suggested by Ken. P.S. I always mark the place where the sash cord is attached to the window, but I think that in this case that will be a waste of time.

Thanks in advance for your comments.

Sylvain.

[Stuart]

I cannot comment on the "physics" aspect of what you say but when I was Googling for an answer I did see that what you should do is raise the window to about 4 inches off the sill( cill),having moved the window inward to get access to the rope and then hoist the weight right up to the top of it's box ( until you hear it clunk ) then fix the sash cord to the window at the same place as the old rope and trim any excess rope .

[Autolycus]

Aye, it is a little, too: leverage (torque, moment, call it what you will) is the product of the force and the perpendicular distance of its line of action from the "pivot point". In this case, the moment is the weight * radius of the pulley, since the line of action is tangential to the pulley.

So changing the length of the cord will make no difference.

How do you know the weights are correct? One could even argue that, since they don't hold the window up, by definition they are wrong. Are you sure the glass has never been changed?

[DeeBee]

The law of levers as you quote is not really valid here as the sash cord should pass over only one pulley at the top of the window. If more pulleys were used then you get into ratio and all that and it does make a difference.

I would guess that the most likely answer is that the glass has been changed at some time for thicker and therefore heavier glass, and this has now "upset" the balance of the window.

the only real solution is to add some extra weight until the sash is balanced.

Hth

DeeBee

[Derek ^]

Hey, I just wondered what abou the weight of layer upon layer upon layer upon layer USW.USW.USW. of gloss paint? Both sides !

Or take it off the window.

DG

[Sylvain VAN DER WALDE]

Thanks for that info, however: Your informant is assuming that the sash cord will have been attached in the correct place. That may not have been the case. We are led to assume that the sash cord was always attached in the same place _from new_. This can't always be the case. I live in a house which is over 100 years old. Does what I say make good sense? Or not?

Sylvain.

[Sylvain VAN DER WALDE]

Well, I did admit it. :)

You've lost me here.

I think that I just about understand this: Fitting a slighter smaller or larger pulley would vary the pulling force on the window. Of course, this is not a practical thing to do.

Yes, I accept that now.

I've changed sash cords on several similar windows in the flat. The weights look alright.

Other factors are involved; one you mention yourself below.

This matter has already been discussed; and no, I can't be sure that the glass has never been changed, as the house is over 100 years old and I've only lived in this flat since 1971. :)

Thanks for your useful contribution.

Sylvain.

[Sylvain VAN DER WALDE]

Yes, that's already been well expained by another poster.

Agreed. Other posters have stated this.

I now agree that it is "the only real solution" as advised now by yourself, and by several other helpful posters. And this is exactly what I will be doing.

Sylvain.

[Sylvain VAN DER WALDE]

Ha! Ha! You're right about the weight of the paint. It's the original window in a 100+ years old house. And no, I'm not touching the paintwork in any way.

Sylvain.

[Autolycus]

Nope.

The weight pulls down on one side of the pulley, the window on the other, so the radius, and thus the "leverage" is the same for both.

But looking alright isn't really much help: they're only right if the window more or less balances.

[Mark]

Look forget all the "physics" crap and think logically This is a simple balance issue, if the window wont stays up the weights are not heavy enough.

-

[Sylvain VAN DER WALDE]

You haven't read some of the other posts: A heavier glass pane may have been fitted; and the accumulation of numerous coats of paint over the years (100+ years actually) will have increased the weight of the window. Some decorators are notoriously dishonest (or lazy), and will not remove the old paint before applying the new one.

Sylvain.

[Sylvain VAN DER WALDE]

As I suggested to a previous poster, you haven't read all the relevant messages. It's _already_ been agreed that what you say is correct, and therefore I've decided to act on that info. Thanks for your post.

Sylvain.

[Douglas de Lacey]

Why do you suppose we have to trawl through old messages in order to help you? Can't you post a proper summary? AFAICS there are several things you haven't told us: is this a recent problem or has it been the case ever since you moved in? Does the window drop right down, or will it stay open part-way? Have you checked the friction of the pulleys? &c.

Douglas de Lacey

[Sylvain VAN DER WALDE]

The messages aren't old. They're all recent. I'm a polite person, and like to answer each post; hence the numbers.

I have. I've added "UPDATE" to the subject line; and in my last message have stated that a solution had been found and that I would act on it.

They weren't asked before by anyone.

It's an old problem.

It drops right down; but the problem is that it won't stay up a few inches, at least as far as the security stops that I've fitted.

Yes.

Sylvain.

[charlieB]

If the window drops right down then the window is heavier than the combination of weights on the 2 cords.

You will either have to reduce the weight of the window or add weight to the cord weights

If the window only dropped an inch or two this would almost certainly have been due to the sash cord being nailed to high on the side of the sash

Looks like your going to have to remove some beading, damage some paintwork and add some weights to the sash cords.

Charlie

[Stuart Noble]

When the lower sash is fully down, the sash weights are up at the top, just behind the pulley wheels. If, when you raise the sash, the cords travel over the pulley normally and there is no slack in them, then it does sound as though the weights aren't heavy enough.