This article details the restoration of locally listed metal church windows at Saint Thomas of Canterbury Catholic church. The windows date from 1965 when the church was built. The nine double hung tilt aluminium windows are operated in pairs by an opening rod linkage via a fanlight catch. Most of the windows had totally seized up. Our job was to get the window mechanism totally overhauled.
Most of the hinges had seized. Many of the aluminium screws had corroded too making it very difficult and sometimes impossible to unscrew them. When we inspected the rod mechanism we found that the right-angled ends were loose fitting.
We had to soak the hinges in oil and manually get the hinges moving again. The hinge leaf attached to the sash had the screws inserted from the inside. The ends of the screws were exposed and riveted over. Some of these had started to fail. The hinge leafs were rocking instead of clamping up to the sash. To remedy this we took out the old screws and replaced those with steel screws fitted with a dome headed nut.
Some of the aluminium screws had corroded so badly that they were impossible to remove. We had to drill these out. In most cases we managed to re-tap the holes. On a few that we couldn't tap we had to use rethreading helicoils. These coils allowed onsite repairs of threads.
The connecting rods and mechanism also needed attention. The original design had aluminium rods, right-angled at one end connecting each pair of windows. Once we had restored a full set of hinges on the first pair of windows we tested the rod mechanism by hand. This showed that when we shut the bottom window the top one was still open by about 12cm. To close the windows the operator would have to push the top window shut separately. We found that the right-angled end of the rod had the hole bored out bigger than on the straight end giving a slack fit on the axle. Without this workaround the windows would have been impossible to shut. This theory was tested using a computer simulation.
We made cad drawings using solid modelling software. This allowed us to simulate the original rod and hinge link mechanism and compare it to our revised one. When we simulated operating the original windows it was impossible to shut them if the rod was fitted with the original right-angled rod assembly. We changed that to a straight rod. The simulation proved that the new rod assembly worked.
We had eighteen straight ends manufactured in sand cast aluminium to replace the faulty right-angled ends of the original linkages. Also we had noticed that the aluminium rods that were originally used were springing in operation. This was giving lost motion in the mechanism. We replaced those with steel. The mechanisms finally opened and closed the windows in pairs.
In the eight weeks to it took to complete the project we:
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