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On the Plane

Traditional Techniques: NarrowBoat, Summer 2015

Andy Tidy

Andy Tidy investigates the evolution of the inclined plane in Britain

The development of the inclined plane is an inland waterway subject that attracts very little attention. This could be as a result of there being no operational examples to visit, or because the majority of plane technology was located on obscure tub boat canals far from the main network and was mostly abandoned by the mid-1800s. Either way, the evolution of the inclined plane is a significant subject in its own right, and follows a discernible progression from its Shropshire origins in the late 1700s through to its shortlived (British) finale at Foxton at the dawn of the 20th century.

Why Inclined Planes?

The use of traditional locks to raise and lower boats between levels has the twin advantages of simplicity and robustness, but has the disadvantages of being slow and, perhaps more importantly, very water hungry.

So imagine an alternative that moves boats up and down hillsides in minutes rather than hours, is far cheaper to build than locks, and uses next to no water. It’s a canal engineer’s idea of heaven and at face value all three benefits are delivered by using inclined planes. So why were they not more commonplace on the British inland waterways, and why are they are often consigned to the footnotes of history books?

The following sequence traces a number of key inclined plane projects, illustrating the technical developments and local variations in the field over a period of 120 years.

1788: Ketley

The story starts with William Reynolds, who was building a short, isolated canal in Shropshire to connect coal mines in Oakengates to his Ketley iron works in 1788. The area had almost no surface water and, with a 73ft vertical drop to negotiate, he ignored the lock option and instead built the UK’s first operational inclined plane.

At its core, Ketley Incline used the ‘tub boat on a trolley’ design, which became standard on tub boat canals. A pair of wheeled cradles ran on two parallel sets of L-shaped iron tracks. The cradles were linked by a strong cable, which was wound round a horizontally mounted drum at the topwith a diameter of 5–6ft. The trolley or cradle had larger wheels at the downhill end than at the upper, so the loaded tub boat sat more or less horizontal during transit.

As a loaded boat descended the incline, its weight pulled the empty boat and cradle back up the other side ready for the next load. In the case of Ketley Incline, the length was about 59 yards. The drum could be braked by an operator and turned by a primitive steam engine (referred to as a fire engine) which pulled the empty tub and trolley up the last few feet as the force exerted by the descending load reduced when it entered the canal at the bottom.

To get the tub boat onto the cradle at the top, a short pound lock was constructed with a sloping base in which the cradle sat. With the boat in position, the water was drained from the lock into a side pond and then pumped back into the top pound by the fire engine. The resulting water loss was negligible and the system was able to transport up to 40 loads per day. The success was such that Reynolds wrote to James Watt in 1789 stating: “Our inclined plane answers my most sanguine expectations ... we have already let down more than forty boats per day each carrying 8 tons – on average about thirty boats daily – and have not yet had an accident.”

The canal and lift operated for 28 years until 1816 – well before the photographic era – so we have to rely on engineering drawings and an image embossed on one side of a commemorative token produced in 1789. This token includes an image of an operator which provides a good indication of the diminutive size of the tub boats used and the orientation of the winding gear.

1791 Onwards: Shropshire Tub Boat Canals Inclines

Shropshire is often described as the cradle of the iron industry and, to connect the expanding mines and ironworks with the outside world, a network of private canals was dug. These ultimately joined up to form the Shropshire Canal network, which extended for about 16 miles through dry, hilly terrain. The ‘cradle of the iron industry’ title may be disputed by historians of the nearby Black Country, but the area certainly represented the early adopters and developers of the inclined plane, pioneering a number of innovations and serving as the prototype for all which followed.

An interpretation of how the Ketley Incline worked, based on the evidence from the token above and from engineering drawings. The large wheel was a brake. Edward Paget-Tomlinson

A Ketley token dated 1789. The diminutive operator is depicted beneath the cable to the right of the right-hand uprights. As at the later incline at Trench, the cable seems to be attached to the top of the cradle.

Hobbacott and Coalbrookdale inclines operated on the bucket-in-a-well system depicted here.

With the Ketley Incline working well, more inclines were built in 1791, including the 350-yard Wrockwardine Wood Incline which rose 122ft from the Donnington Wood Canal and whose path can still be traced through the woods. A few miles further west, the less steep 600-yard Windmill Incline was constructed to lower boats 125ft down the other side of the hill.

The Shropshire Canal made a connection with the River Severn at Coalport via the impressive 300-yard Hay Incline, which was built in 1792 and dropped 207ft in what are now the grounds of Blists Hill Victorian Town. This incline has been cosmetically restored and reveals an evolution in design, with the problematic top pound lock abandoned in favour of a low bund, or mound, which retained the water in the top canal and over which the tub boat and cradle were hauled with the assistance of a steam engine. Whilst the ex British Rail tracks used in the restoration are somewhat incongruous, they do offer a sense of scale to the site and it is easy to imagine loaded tub boats moving up and down the slope.

The top bund of Hay Incline, publicly accessible within the grounds of Blists Hill Victorian Town, one of the Ironbridge Gorge museums.

The recently discovered Coalbrookdale water adit, which is believed to have fed water into the buckets that powered the inclined plane.

Shropshire Canal engineers led the way in inclined plane technology. At the far end of the Horsehay Branch, the Brierly Hill Incline was built in 1789 to connect Darby’s ironworks in Coalbrookdale to the canal. This incline didn’t carry the tub boats but rather carried smaller boxes or containers which were transhipped from the tub boats.

The interest in this incline is its unusual method of propulsion. The loads were mainly to be carried uphill, and the engineers appear to have used surplus water as the motive power. The present owner of the site discovered the top of two huge brick-lined pits under his drive, which connect to an adit exiting lower down the hill, and also a tunnel beneath his garden. This arrangement is confusing at first but reference to the ‘bucket-ina-well’ approach taken at Hobbacott Incline in Devon, built 34 years later in 1823, suggests that Brierly Hill Incline may have been a smaller prototype.

It appears likely that two huge buckets were suspended in the 120ft pits, connected by a rope which was wound round a big drum. This drum was also linked to a cable attached to two cradles, possibly via a gearing mechanism. When goods were to be hauled up, water was passed along the upper tunnel and into one of the buckets, filling it up till it was heavy enough to pull the load up the hill. When the bucket had descended, thewater was drained off through the adit and the bucket was raised back up, along with the lower cradle, by the weight of the other water-filled bucket.

The Shropshire Canal system offers a further incline at Trench, the last to be built on the Shropshire Canal network, in 1797. This moved tub boats 75ft between the Shrewsbury Canal and the older Wombridge Canal above. The incline used the now conventional ‘tubon-a-trolley-over-a-mound’ approach, but this one had the distinction of being the last operational incline plane in Britain, finally closing in 1921 after 124 years of operation. Because of its longevity it is one of the few which have been thoroughly photographed andprovides an excellent insight into how these mechanisms operated.

One of the limiting factors of inclines at this stage was the method of transferring the boats from the top pound to the incline. Tub boats were loaded end-on, as their short length allowed them to be successfully manoeuvred over the mound. Such an operation would probably have broken the back of a loaded full-length narrowboat, so a better method of transfer was needed for longer boats.

Trench Incline is the only one for which detailed photographic records exist. Here, the effect of different sized wheels in keeping the wooden tub boat level is clearly demonstrated. The rope or cable is attached to the top of the cradle’s frame, rather than the chassis as might be expected from later railway inclines. Waterways Archive

The relative sizes of a Shropshire tub boat and the preserved Severn trow Spry can be seen at Blists Hill Victorian Town at Ironbridge.

The dramatic view looking down Trench Incline with the two cradles about to pass half-way and the many chimneys of the local industries beyond. Waterways Archive

The engine house at the top of the Trench Incline, with a tub boat in the left-hand incline. Waterways Archive

1792: Worsley Mine

During the same year that Trench Incline was completed, the Duke of Bridgewater was busy building an underground incline at Worsley to connect two navigable levels of what was to become over 40 miles of underground mine navigations. Given the close connection between the Duke of Bridgewater and the Duke of Sutherland – who was the driving force behind the development of the Shropshire network – it is no coincidence that the construction techniques were similar.

The underground incline was 453ft long and 106ft 6in high, comprising two parallel tunnels which followed a conveniently angled rock formation dipping at a 1:4 gradient. Whilst no pictures exist of this subterranean incline, we do have access to a meticulous record known as Description du Plan Incline Souterrain written in 1812 by the Duke’s heir, who nearly lost his life as he slipped and fell when inspecting one of the shafts.

In this case the lifts carried the ultra-narrow ‘starvationer’ boats, larger than tub boats but smaller than fullsize narrowboats.

Technology had advanced, and this mechanism was able to carry a 21-ton payload: the boat (4 tons), the cradle (5 tons) and 12 tons of coal. The motive power was the weight of the coal and boat on the downhill cradle hauling an empty boat up. As in Shropshire, a 2½in-diameter cable was wound round a drum and up to 30 boats could be manoeuvred in an 8-hour shift.

This incline operated successfully for 25 years until 1822 when it was dismantled, but mine inspections continued through to 1961 at which time one shaft was clogged, but the other remained clear and the pulley bearing was still in place.

Inclines of the South-West

The early successes led to a glut of inclined plane projects, mainly concentrated on the isolated tub boat canals of Devon, which picked up on the technology developed in Shropshire and expanded the size and capacity of the tubs and pioneered innovative methods of powering the inclines.

Combe Hay Incline on the Somersetshire Coal Canal was built in 1799, following a disastrous experiment with the submarine caisson lock. No boats were lifted here; instead wheeled carts were moved on rails for six years as a transhipment stop gap whilst a flight of conventional locks was funded and built.

The Morwellham Incline on the Tavistock Canal was built as another transhipment structure in 1816 to drop copper ore 237ft to the Tamar estuary. Four-wheeled tipping wagons were used on twin tracks with larger wheels at the downhill end. The key development at this location was the source ofmotive power: a 28ft-diameter overshot waterwheel, with the water supplied by a feed along the canal itself.

The Bude Canal was a tub boat venture and when completed included six relatively short inclines, five of which were powered by overshot waterwheels: at Marhamchurch, Veeland, Merrifield, Tamertown and Bridgetown. A longer, sixth incline was built at Hobbacott, overcoming a 225ft height difference via a 935ft incline, this time powered by the bucket in a shaft as previously seen in Coalbrookdale. The difference was that, rather than moving small 1-ton payloads, technology had advanced and the Bude tub boats were capable of carrying much larger loads – some up to 20 tons.

The twin shafts at Hobbacott were 13ft in diameter and each bucket contained about 15 tons of water, enough to pull a loaded boat up the 1:4 incline in about four minutes, half the time it took the 16hp standby steam engine to do the same job.

1850: Blackhill

The next evolutionary step in the story of the inclined plane occurred north of the border in 1850 on the Monkland Canal (which linked to the Forth & Clyde in Glasgow), where severe capacity issues at a flight of locks were coupled with an inadequate water supply. Here, at Blackhill, a bypass incline was built and for the first time a British inclined plane was built to carry full-size canal boats, albeit only empty ones and only uphill, easing the congestion on the overworked flight of locks.

The Hay Incline at Coalbrookdale in the early 1870s.

A modern drawing of the Hobbacott Incline, which operated on the bucket-in-a-well system. Barry Hughes

To provide adequate support, the boats rode afloat in a wheeled ‘wet dock’ facing into the hill. The wet dock was preferred over the dry cradle successfully employed on the tub boat canals because it avoided the strain placed on the craft had they been hauled over a bank at the top. The caissons were 70ft long by 13ft 4in wide with the depth of water limited to just 2ft as all the uphill boats were empty. As a result, the water carried was minimised, reducing the overall weight.

This was inclined plane technology pushing new boundaries, with each caisson riding on ten pairs of wheels as it ascended a 1:10 gradient. To minimise the risks associated with such great weights, a rack and pinion system was deployed automatically if the load came off the cable. The seal at the end of the caisson was by guillotine gates, with the caisson and fixed structure initially attached to each other by manually operated screw jacks, a system later changed to a more effective hydraulic ram.

For most of the ascent, the caissons balanced each other, but as the lower caisson became submerged in water the two 25hp high-pressure steam engines had to operate at full power to haul the uphill tank into its final location. These caissons travelled at about 2mph and completed a run from bottom to top in 5–6 minutes. In an emergency the steam engines were capable of delivering all the power needed by the 16ft diameter winding drums.

1901: Foxton

In some ways, the 1901 Foxton Incline was to planes what Pontcysyllte is to aqueducts. It represented the zenith of the British inclined plane technology. However, whilst it was still operating successfully after 10 years, it carried only a tiny fraction of its potential capacity and was decommissioned on economic grounds.

The plane incorporated all the best elements from the past, but was constructed on a scale which allowed pairs of narrowboats to be lifted, floating, broadside-on in a wet dock, in 12 minutes as against the hour taken to negotiate the old locks, which used 25,000 gallons of water per cycle. The key facts were as follows:

• Rise: 75ft 2in;

• Gradient: 1:4;

• Each tank was 80ft x 15ft x 5ft;

• Each tank contained 230 tons of water/craft and could accommodate two 35-ton narrowboats or one 70ton barge;

• Tanks were connected using steel cables with a 7in circumference;

• Guillotine gates were raised and lowered using hydraulics;

• Both tanks were in balance with a small 25hp engine to overcome friction;

• Three men were needed to operate it;

• Capacity, calculated on 70 tons in both directions, was 8,400 tons per 12 hours, giving a theoretical maximum capacity of 2.5m tons per annum;

• Total cost of construction was £39,244 (£4.2m at 2014 values).

This is the only photograph that NarrowBoat could locate showing an inclined plane on the Bude Canal. The location is unknown, but it depicts the top of one of the five planes powered by an overshot waterwheel with tub boats waiting to descend. Waterways Archive

A diagram of Blackhill Incline on the Monkland Canal taken from an engineering article of the time. The Mitchell Library, Glasgow

An experimental inclined plane set up at Bulbourne prior to placing the order for the full-size Foxton Incline. It was photographed at an official inspection on 13th November 1896, the caption to the photograph calling it variously a ‘slide’ and a ‘lift’. Waterways Archive

An interesting juxtaposition of the inclined plane at Foxton and the flight of locks which continued to be operable throughout the incline’s existence, despite the intention that it should replace them. George Hancock Collection

Foxton incline with the nearest caisson, or water tank, in the lower position. Railway & Canal Historical Society

Planes Abroad

Opened in 1969 and designed to take 350tonne péniches, the Arzviller Incline on the Canal de la Marne au Rhin in France replaced a flight of 17 locks and operates on the same principle as Foxton, but with a single caisson counterbalanced by the two massive concrete weights seen just above it.

On a far larger scale, taking 1,350-tonne barges, the Ronquières Incline in Belgium operates with two caissons taking boats longitudinally as did the Blackhill Incline. It was opened in 1968, the year before Arzviller.

On the Ostróda–Elblag Canal in Poland, opened in 1860, the flight of five inclined planes operates on the early principle of carrying boats dry in a cradle. This has the advantage of greatly decreased weight, but puts strain on the boats and limits their size. Power is provided by waterwheels at the four original inclines and by a water turbine at the fifth.

Inclined planes met with more success in mainland Europe, both in survival of early examples and construction of new ones. These examples from Poland, France and Belgium show three that can be visited and used today.

A beautifully illustrated brochure was published by its engineer Gordon Thomas shortly after completion, presumably in the hope of winning similar contacts elsewhere. This is full of facts and images revealing in detail the technical approaches taken to overcome a number of key engineering challenges.

Whilst vertically rising guillotine gates had been used elsewhere, the joining of the wet dock to the upper masonry relied on hydraulic rams. These pushed the tank against an accurately finished surface, there being enough play in the axles to allow for several inches of lateral movement. The resulting wooden butt joint allowed very little water to escape whilst boats were being manoeuvred.

An innovation was to minimise the impact of the reducing weight of the lower wet dock as it entered the water at the bottom of the incline, a problem which had previously been overcome elsewhere with mechanical force.At Foxton this effect was minimised by reducing the gradient over the last few feet of the top of the incline and thereby mirroring the reducing gravitational pull. A downside to this variable gradient approach was that the top tank would not remain level as it approached the end of its climb, and would rotate, spilling water. Thomas’s solution was as neat as it was ingenious. He simply added an extra set of wheels to the leading edge of the tank and an extra rail at the top which mirrored and offset the changing gradient, letting the entire mechanism remain perfectly level.

As a feat of engineering, Foxton Incline was a huge success, but far from representing the dawn of a rejuvenated age of canal transport, it heralded the start of a slowly fading sunset. The rise in traffic failed to materialise, and by 1911 boating operations had reverted to the locks. The mothballed structure was sold for scrap in 1928, leaving just a shatteredjigsaw of concrete spread across the Leicestershire hillside.

Whilst Foxton may represent the high point of British incline plane technology, the baton was picked up on the continent where the larger waterways continued to develop into the 20th century, and ever more extraordinary mechanisms were devised for transporting boats from one level to another.

However, Foxton represents the end of the evolutionary line as far as the UK is concerned.

Inclined to Read More?

The full story of inclined planes – and boat lifts – worldwide is excellently told in Canal Lifts and Inclines of the World by Hans Joachim Uhlemann, translated by Mike Clarke, available from Inland Waterways International