One of the first things you notice as you approach the Bancroft Museum must be the chimney, the sheer size of it towering above the mill. Visitors often have many questions to ask, some are easier than others to answer, but I will try to answer some here. If you want to ask a question, please ask away!
One of the most frequently asked questions that is asked is, how tall is the chimney? The simple answer is about 124 feet tall for those us of us still using feet and inches, or nearly 38 metres for those who prefer metric. This is measured from ground level and doesn’t include foundations.
This is a view that not many are privileged to see, it is taken from the bottom of the chimney looking up, and it is from here that you get an impression of its height.
Judging height is always difficult, so this next picture shows how far the chimney would stretch if it was lain on its side
How do they check the chimney is vertical? During construction a plumb bob would have been used. When steeplejacks visit they will check for movement as they inspect the chimney.
How wide is the chimney? The chimney’s external diameter at ground level is 11feet 6inches, or about 3.5metres. As the chimney rises, it tapers as this makes the chimney more stable, and is also cheaper to build as it uses fewer bricks, (cost being very important if you are building from scratch)
Why is the chimney so tall? the chimney needed to be tall to help with the draught up the chimney. The better the draught, the more efficiently the boiler could run. Running the boiler efficiently meant it was more economical, saving the company money. Weaving cotton was very big business in Barnoldswick, with Bancroft being the last of the thirteen mills that the town once had. Keeping costs down was necessary to keep businesses competitive.
Why has it got an oversailer? The oversailer is the extended area at the top of the chimney. As the hot air from the boiler reaches the top of the chimney it cools and falls down the sides. Because in comparison to the normal air around the chimney, the exhaust air is still very hot, it can cause erosion to the chimney itself. The oversailer prevents the air “falling down” the sides of the chimney, causing eddies, and so helps to reduce erosion. At Bancroft, the main part of the oversailer on the chimney is constructed of stone, whereas the chimney is of a brick construction.
More facts about the chimney in the next time. In the meantime, if you have any questions, please contact info@bancroftmill.org.uk and we will do our best to answer them.