This week we will be delving into the world of Ekki wood and it’s marvelous abilities in water. Over to Power volunteer Bruce Williams for more details.
Every 35 years the main sluice gates in the headrace, which control the flow of water from the mill pond to the mill, tend to deteriorate. The wood begins to rot and in some cases leaves a number of holes within the gates. As a result, it’s no longer possible to shut off the water flow to the mill, and this obviously needs to be avoided at all costs as it could cause serious damage.
This time round the sluice gates were restored by our ‘in house’ maintenance and engineering teams. First of all baulks of suitable timber were bought and obtained. The wood we used was called Ekki, which is a tropical hardwood which is durable and long-lasting. This type of wood is often used in marine applications as it is resistant to insect attacks, making it a suitable hardwood to use for our gates.
The timber was then finished to size in our joinery workshops, and afterwards each of the ten planks had to be individually drilled in our engineering workshop to take the stainless steel rods which hold the gates together. Now work in the headrace could begin.
First a stop board was placed in the headrace to reduce the flow of water to manageable proportions – this allowed the headrace to be drained to the point where there was only about six inches of water by the bottom of the gates.
Once drained the work could begin on the first gate. The bolts securing the original gate to the lifting mechanism were removed along with the bolts on the top of the tie rods. From here the old planks could be lifted out one by one.
Now with the gate out of the way, it was then possible to remove the guides on either side, which the gate slides onto. The wooden parts were quite rotten in places, so there was no question that these had to be replaced.
New guide rails were then fitted into place, and a template was fitted to mark the locations of the bolt holes for the lifting mechanism. This was necessary as the cast iron brackets needed to be recessed into the face of the gate to fit.
Once the template was completed, the top planks of the gate could have the recesses routed out before they were installed. The gate was then assembled by lifting each plank and lowering it down between the guide rails, and over the four tie rods. When all ten planks were in place, the tie rods were bolted up to secure the planks into one gate, and then the cast iron brackets of the lifting mechanism were bolted to the gate.
The final job was now to secure a rubber sealing strip along the bottom of the gate. This makes a better seal that will conform to any slight imperfections in the concrete threshold on which the gate sits. Finally, the first gate was now completed.
When working on the second gate, we found that the horizontal beam which supports the lifting mechanism was not attached to the vertical post at the far side, as the top of that post had become rotten. While working to replace this gate, we secured it temporarily with steel braces, but it was obvious that this would need to be repaired.
On close inspection of the other two vertical posts we found yet again that there was some rot. However, this was easily removed and replaced to prevent any further deterioration. Nevertheless, on the far post it was necessary to have a steel bracket made to support the horizontal beam in place, while the top of the post was cut out. A replacement part was fabricated out of oak and bolted into place, so that everything is now firmly attached once more.
The final job will be to repair the concrete threshold under the gates, as this shows some signs of wear. Once repaired, the gates will seal better, and it will again be possible to exert control of the flow of water through the headrace.
Thank you to Bruce for producing this blog and the photographs to go with it.
Thank you to all of you too. The National Trust is a charity and without your support we would not be able to carry our the vital work which keeps Quarry Bank running. To find our more about our conservation work and the Quarry Bank Project, please visit our website.