As with many china clay works, Wheal Martyn was built on a hillside to help the clay slurry move around by gravity. However, some settling pits here are located above the mica drags and needed to be filled with clay slurry by a pump. In about 1902 John Lovering built the 18ft overshot waterwheel and slurry pump to fill the pits with clay slurry. The clay slurry was lifted by a bucket lift, (a piston fitted with a valve which works inside the cast iron pipe). It can lift about 26 gallons (120 litres) per stroke. The slurry pump, which is operated by the waterwheel, is the only surviving pump of its type out of an estimated 200 which were in existence throughout the clay industry in Cornwall.
When clay slurry reached the Wheal Martyn works it was pumped around the site using the slurry pump. The pump was powered by the 18ft overshot waterwheel connected via a wire to transmit the power. A balance box was needed to keep the wire cable in tension, to partially compensate for the weight of the pump and keep it operating smoothly.
The waterwheel is part of the Scheduled Ancient Monument and now features as a key element of our ‘Historic Trail’ on site. As well as being extremely popular with visitors it is hugely important in educational terms, demonstrating the movement of clay and the innovation of the people involved in its creation.
- +The Need
Over recent years it has been identified that major restoration and preservation works are required in order to preserve the 18ft waterwheel and associated workings. The following issues are highlighted in the Conservation Management Plan (completed in July 2013, to identify and plan for the preservation needs of the Scheduled Ancient Monument over the next ten years) and were also noted by Historic England during a site visit in February 2015.
The problems associated with the small water wheel are deterioration of the wooden buckets to the extent that the wheel often ceases to operate and that the cast iron of the wheel is in fact cracked. Repair and restoration of this is seen as a priority since this working complex of wheel, flat rods and slurry pump is not only an important part of the museum’s display but also is the only working example in Cornwall. Other issues include rusting metal ties, rotting wooden launder leading to the wheel, rotting wooden beam which supports the balance box and the metal chain which diverts water away from the wheel and down a shute is rotten.
As part of the Conservation Management Plan, a condition survey was completed for the waterwheel which states that it is evident that the on-site team are only able to undertake emergency repairs to the waterwheel and that the constant attack from water and the elements are accelerating the rate of decay to not only the timber elements of the structures but also the steel supports and fixings. A more substantial schedule of works is required within the next two to five years to ensure that the waterwheel and associated structures remain in a structurally sound and working condition and do not rise to a level 4 risk (PWH Surveyors, July 2013).
Now nearly three years on from the Conservation Management Plan, the water wheel has deteriorated further to a point where it cannot function properly and is often out of action requiring frequent remedial repairs to keep it going. This constant ‘patching’ is not sustainable and becoming increasingly difficult to do in a suitable way to keep the wheel operating. Periods where the wheel is out of action causes further detriment to other parts of the Scheduled Ancient Monument, including the slurry pump and other features, as a result of water not being pumped around the site, causing wooden features to dry out and deteriorate.
- +The Work
The refurbishment work includes replacing all the wooden elements including the buckets, inner wheel, launder and launder supports with prime European oak. Steel tie bars which brace the wheel and steel receiving sockets which join the launder support to the granite beneath will also be replaced and the cast iron waterwheel will be stripped and repainted.
Once all funding is secured we hope to commence the works in the Autumn of 2016 with a target date for completion by the end of November 2016.
COSTS AND FUNDING
The overall cost of the refurbishment works is in the region of £32,000, with the major cost being the European oak.
At June 2016 £20,200 has been secured towards the works as follows:
- • £18,000 from the Association For Industrial Archaeology
- • £2,000 from the Sylvia Waddilove Foundation
- • £200 donation from a member of the China Clay History Society