Under pressure

THERE IS A LOVELY STRETCH of the railway from London Paddington to Devon and Cornwall. It is between Exeter and Newton Abbot. The train runs from Exeter along the western shore of the wide estuary of the River Exe, then along the seashore between Dawlish Warren and Teignmouth (often between the base of cliffs and the sea), and finally turns inland to run along the shore of the broad River Teign to reach Newton Abbot. This scenic stretch of track helps make the trip to the far southwest extremely pleasant.

In August 2020, our friends in Torquay took us by car to Teignmouth and other points along this scenic rail route. It was fun to stand near the track and watch trains rushing past. One of the places we visited on that trip was the small village of Starcross, where a small passenger ferry crosses the Exe, carrying pedestrians, cyclists, the crew and their small dog to and from Exmouth. Near the Ferry embarkation point which is reached by crossing the railway via a footbridge, I spotted something quite surprising for this day and age of concerns about health and safety. A small gate (‘kissing gate’ variety) for pedestrians allows people to cross the tracks to reach the beach beyond them. This crossing is unguarded and permits folk to walk across two lines of track along which trains hurtle every few minutes. A sign exhorts those foolhardy enough to make use of this crossing to “Stop, Look, and Listen”.

Near the pier where one boards the ferry at Starcross, there is a brick building with white stone facings and a tall square brick tower. This edifice that has an industrial appearance stands close to the railway lines. In days gone by, it was a pumping station for a railway whose trains were propelled by compressed air, the so-called ‘Atmospheric Railway’.

The South Devon Atmospheric Railway, which followed the route taken by trains today, ran between Exeter and Plymouth. The construction of the westbound line from Exeter, The South Devon Railway, gained Parliamentary authorisation in mid-1844. Isambard Kingdom Brunel (1806-1859) was the engineer in charge of constructing the South Devon Railway. Given the then current power of steam locomotives, he decided that they would not have sufficient strength to deal with some of the gradients along the route. He opted to use propulsion generated by gases under pressure – the atmospheric system.  One of the pioneers of atmospheric railways was the English engineer and politician Joseph d’Aguilar Samuda (1813 –1885), whose ideas influenced Brunel.

Trying to put it as simply as possible, here is how I understand that the atmospheric railway system worked. A cylindrical metal traction pipe was laid between the railway tracks. This pipe had a longitudinal slit facing upwards. The slit was sealed shut by leather flaps that kept the pipe airtight when it was filled with compressed air provided by a series of pumping stations along the line. The building we saw at Starcross was one of these units, whose engines could generate between 45 and 82 horsepower.

The pumps injected air into the slitted longitudinal iron pipes (20 inches in diameter), whose leather flaps prevented escape of the gas. The trains using the atmospheric system were pulled by specially designed traction cars. Each of these cars was attached to a piston that fitted snugly within the air pipes running along the track. The attachment of the piston to the traction car was fitted with a mechanism that opened the short section leather flap immediately beneath it. The compressed air exerted pressure on the end of the piston, causing it to move along the pipe. Being attached to the traction car, the motion of the piston caused the car to move along the tracks. As the traction car was attached to the carriages, they were pulled along by the air-propelled traction car. As soon as the traction car moved along the track, the part of the flap that had been open momentarily, then closed, and the next short section opened briefly. What I have described is an oversimplification that ignores how the system dealt with points, level crossings, etc.  More detail is available for those interested on various websites (e.g. https://railwaywondersoftheworld.com/atmospheric-railway.html and on Wikipedia).

This system of propulsion was able to propel trains at speeds up to 70 miles per hour, although this speed was rarely attained. It also allowed trains in the late 1840s to overcome gradients that would have been too challenging for the steam engines at that time. The system was abandoned in about 1848. The leather valves caused numerous problems. Air leakage was one of these. Throughout the year, the leather dried out and became too stiff for use.  In winter, frost also damaged their flexibility. Throughout the year, they provided food for rats, whose activities were detrimental to their efficient functioning. The rat story is oft quoted but WG Hoskins, author of the much-respected book “Devon” notes that the atmospheric railway:

“… was a complete failure mainly because of the decomposing action of water and iron on the vital leather component of the valves … In September 1848 the line was worked by locomotives and the ‘Atmospheric Caper’ was abandoned for good, after more than £400,000 of the company’s money had been wasted. Brunel had made a tremendous mistake …”

I wonder whether with today’s synthetic rubber the experiment could be repeated, thus creating a railway system that makes little use of diesel engines. I suppose that electrification of the line might be a more practical solution.

Today, the largest relics of the short-lived Atmospheric Railway are the well-built pumping stations such as the one next to Starcross Station and the ferry embarkation point. It was built in 1845 and designed by Brunel. It consists of two blocks and the tall, solid looking chimney (https://historicengland.org.uk/listing/the-list/list-entry/1097684). In 1869, the east block, which used to house the boilers, was converted for use as a Wesleyan chapel, and served this purpose until 1950.  The west block used to house the beam engine that used to compress air. This block was later converted to an engine shed for housing steam locomotives until 1981, when it became home to a museum related to the Atmospheric Railway. In its heyday, the Atmospheric Railway was powered by 11 pumping stations, of which only four remain standing (Starcross, Totnes, Dawlish [not much left to see], and Torquay). There is one other souvenir of the ill-fated system at Starcross. This is a pub opposite the station. It is called ‘The Atmospheric Railway Inn’. Sadly, the covid19 pandemic has resulted in it deciding to remain closed for the foreseeable future.

I had never heard of the Atmospheric Railway until we visited our friends in Torquay. Had it not been for their suggestion that we took a trip across the River Exe on the ferry, I might never have noticed the former pumping station at Starcross and remained in ignorance of Brunel’s adventurous experiment in railway technology.

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