I have a set of four tilting, double glazed, two part, sash windows (installed in 1990) which are beginning to rot and so I want to remove and get fixed. However, there does not seem a way to get them out. They are held vertical by four rack bolts and a central pivot. There is no way to detach the pivot, nor remove it from the track. The spring mechanism and the dimensions stops the twisting of the sash to get it out that way. Looking at the whole window it would seem to have been installed complete. Two wooden window makers, an "old school" joiner and a big double glazing company all say they have never seen a system like it. Does anyone recognise the mechanism and is there an obscure way to take them out? I suspect I will have to do my best with expoxy but to add to the difficulty there is a conservatory in the way! Thank you.