Sunday, 2 February 2014

Combe Hay - upper section

Combe Hay - the top end
February 2014

Combe Hay has a lot to offer the canal enthusiast and justifies a lingering approach, savouring the great remains which are there to be enjoyed.  

Comb Hay top lock and channel to inclined plane / pumping engine

I spent a very enjoyable couple of hours exploring all the sections of the Combe Hay area I could legally access, and a few where legal rights of way had to be viewed as a somewhat elastic concept. What I didn't feel I could do in all conscience, was to go blunderimg around the sites of locks three to eight which are clearly in the grounds of Caisson House and were well protected by barbed wire, indicating that casual visitors are not welcomed.

Given the material to be covered I will divide the Combe Hay reports into three, the upper section (this post), the middle section containing the thick of locks and the lower section which includes the buried/ less restored locks plus the channel to the base of the inclined plane.

Most canals seem to have something unique about them and for the SCC, its USP undoubtedly lies in its varied attempts to climb 135 feet from the Kennet and Avon level to the summit pound. 

Attempt one - The Caisson Lock
The canal builders were working to a budget and wanted to avoid the cost of a long flight of locks. They therefore cast around to alternatives and settled on the untried Caisson Lock concept. This was the brainchild of Robert Weldon and to give its his full title it was the Hydrostatick Caisson Lock. He had made a working model for the tub boat canals in Oakengates, beneath what is now Telford, but its interesting to note that he was never daft enough to actually try and make it work, even for their small 5 ton tubs.

Design for Caisson Lock as found on the SCC website

To be honest you need to see a drawing of this idea, which is explained very thoroughly in the SCC website.

But put simply, they decided to build three super deep locks which would never actually empty. Instead the canal boat would be put into a wooden "submarine" a bit like a torpedo in its tube, and the whole assembly would then be sunk with the boat floating inside. When it reached the bottom the end would lock into a watertight seal and the door opened letting it float out and away.

Fast, quick and uses almost no water. Perfect, fantastic and great - lets order 1000! Oh, but before you do, listen to that nagging word of caution in the back of your head. Its telling you that it sounds like a disaster waiting to happen and so it was. The builder managed to get the top one working and for some reason known only to themselves the SCC Committee decided to take a ride in it. Of course the inevitable happened and it became stuck and the committee was very nearly suffocated before the water was drained off and the caisson opened. Needless to say this was enough to see the whole project abandoned in or around 1794.

Attempt two - The inclined Plane
I suspect that the SCC Committee had contact with the Duke of Sutherland and his canal network at Lilleshall. Not only had the ill fated Caisson Lock come from their operation, they also made extensive use of inclined planes. The SCC therefore installed three locks at the foot of the site and then an inclined plane to raise the boats about 110ft.

Navigable feeder from Pumping Engine

This system was made to work and the long approach channels can still be found and top and bottom. For the purposes of this post we will look at the upper channel which curves around Caisson House and follows the contour round the hill to the site of the old Pumping Engine.

It would appear that the top of the inclined plane was somewhere very close to where Caisson House stands today, but the feeder channel to the Pumping engine was not only a water channel but also a way of getting coal to its boilers.

Remains of the pumping engine

Today the dry channel is apparent and the foundation of the pump house remains to be viewed.

The lifespan of the inclined plane was short, probably less than 10 years, and my guess is that like so many other inclined plane ventures, it failed do the unreliability of the technology with buckling tracks and the cost of maintaining steam in the winding engine. Similar inclines worked well on the Shropshire Canal but these only carried tubs weighing about 5 tons plus cradle, whereas the Combe Hay versions would be carrying 28 tons of loaded craft plus water filled tank and cradle. Even 100 years later in 1900 a similar plan was implemented at Foxton, but this was also abandoned in after a few years in favour of conventional locks.

Attempt three - the 22 Locks
Within a few years the inclined plane was abandoned and by 1804 the funds had been raised to build a flight of conventional locks - the same ones we see today.
A special act of Parliament was needed for the Lock Fund and the end result was a flight which was rugged and almost northern in quality - big blocks of stone all over the place. I bet they were dreadful pi##ers! 
One odd feature of these locks was their narrowness. They were built to carry narrow craft which when strapped together fitted the Kennet and Avon locks. As a result they were built to a width of about 6ft 8in.

 Lock 1 of the Combe Hay flight

From the top at the entrance to Caisson House you can wander around the top lock and see lock No2, its leaning sides held apart with tree trunks and remnants of sagging lock gates - like a surreal Salvador Dali painting.

Lock No 2 - Combe Hay

An old map of the Combe Hay site taken from the SCC website.

I have to acknowledge the SCC website which is a veritable treasure trove of history and which I have used to provide a superficial overview of the area. I would urge you to visit their site for a much fuller history.

1 comment:

Anonymous said...

Haven't visited Combe Hay and Caisson House in something like 30 years but went there several times in the 1970's. My understanding of the inclined plane was that the goods were transhipped top and bottom, (i.e. boat to wagon and wagon back to another boat)- very labour intensive and expensive which is why they only did it for a few years. I don't believe that the boats travelled the inclined plane.