Claverton Pumping Station
Wednesday 23rd March represented the 13th meeting of the CRT National Council, this time gathering in the beautiful city of Bath.
One particularly positive dimension of the Council meetings is the provision of a guided tour around what is usually one of the lesser known elements of the CRT estate. This time it was the turn of the Claverton Pumping Station on the banks of the river Avon, about three miles upstream from the town.
Our visit coincided with one of those mornings when BBC Weather indicated grey cloud with two drops of rain - in other words it would be p*****g down! And on this occasion the good old BBC were spot on, not that it dampened our enthusiasm for a brief tour.
The station is spread over three levels and we entered beside a swollen mill pond which was pouring two tons of water over 48 wooden slats fixed to 24 foot wide and 17ft diameter wheel which rotates every 12 seconds. Given the fall in the river at this point there is not enough height for an overshot wheel, so instead the water rushes onto the wheel mid way up, producing more power than the sort of undershot wheel I am more familiar with from the Norfolk watermills.
This huge wheel originally drove a traditional watermill but with the construction of the adjacent Kennet and Avon Canal an additional water source was needed. The mill was therefore converted to house a beam engine uniquely powered by water, lifting 50 gallons of water with each stroke and pumping nearly 100,000 gallons per hour 48 feet to the canal. To put that in perspective, its enough to fill two locks each hour. All this is achieved using free power supplied by the river.
As a walked under the bobbing and thrusting rods I was entranced by the geometric ingenuity of what I later learned was the Watt linkage, Watts huge contribution to the development of the Beam Engine. When I got all excited about it the visitors around me gave me rather strange looks so I will try to explain the problem the linkages overcame.
When a nodding beam engine seeks to convert power into an upwards and downwards motion for a pump it is hampered by the fact the the end of the beam arcs as it moves, so its end does not stay directly above the pump cylinder. Most engineers overcame this problem by using a cable on a rim which provides the desired vertical motion, but a cable can only be pulled, not pushed. Watts device involved two hinged bars hanging down from the beam which can swing to and fro. The alignment is then achieved by a bar attached to both the drop bars and the external framework, gently compensating for the movement created by the arc. I am not sure I am explaining this very well so you had better pay the site a visit and see it for yourself. My thanks to Phil Prettyman for the explanation.
This unusual structure continued quietly about its business from its construction in 1813 till 1952 when it fell into disuse. Then a group of volunteers set about its restoration, a group which continues to this day under the watchful oversight of CRT, the site's owner.
These days the mechanism is fully operational and they just need to reestablish a pipe under the adjacent railway line and they will be able to join Crofton as the second operational beam engine supplying water to the canal.
This site is well worth a visit if you are passing on one of their monthly open days.