A Sound Surround

In an earlier article, a comment questioned what might have been originally fixed to the edges of the large hole in Sentinel 7109's cab roof from which the chimneys protruded.

At the time, I did not know the answer although Norman thought he had seen something that had come from the old cab roof. Despite much searching, I'd not found anything but then on Sunday 11th Nov. 2012, I spotted something amongst 7109's bits and pieces that was obviously the right item. (Had someone been hiding it as I'm sure it wasn't there before?)!

Chimney Surround plate

Judging from the fixing holes around the edge which match those on the old cab roof, this is the correct original item. But why have an extra sheet to reduce the size of the hole at all?

The hole matches the chimney unit size

When looking at the hole size relative to the size of the twin chimney units, it becomes clearer.

Easily takes the two chimney units (1)

With the chimney surround also in place, there will be a fairly close fit to reduce rain coming in.

Easily takes the two chimney units (2)

The main reason for doing it this way is that when the surround plate is removed, there is space to remove the chimney units without having to take the whole roof off (not that this is difficult, of course!).

A second reason is that if the hole in the cab roof does not match the position of the chimneys mounted on the top of the boiler, it is a lot easier to reposition a small plate like this than to move the whole roof.

Another mystery solved! Now how many years did that take?