Atmospheric railway track, Didcot Railway Centre
Starcross Pumping Station, Devon
To modern eyes the atmospheric railway, with its leather flaps and rats in the pipes, seems a Heath Robinson contraption, but when it was devised by a gas engineer, SamueI Clegg, and the brothers Jacob and Joseph Samuda and patented in 1839 it attracted the serious attention of the brightest brains in the engineering profession.
The idea was to evacuate the air from a tube between the rails, so that the vacuum in front of a piston underneath the train would cause air behind the vehicles to propel them forward at speed, without the weight of a heavy locomotive and the fuel it had to carry. The slot that admitted the piston was sealed by leather flaps that maintained the vacuum before and after the train passed.
This worked quite well on a 1¾-mile extension of the Dublin & Kingstown Railway in Ireland. This former horse tramway had an average gradient of 1 in 110, and opened in 1843.
Trains carrying up to two hundred passengers weighing 38 gross tons were propelled by the vacuum in a tube between the running rails at speeds of up to 40mph.
On one occasion the piston carriage set off without its train, and covered the entire line in 75 seconds at an average speed of 84mph.
The London & Croydon Railway ran trains using the atmospheric system between Dartmouth Arms (now Forest Hill) and Croydon from January 1846.
The interior of the pipe was sealed by a mixture of tallow fat and beeswax which melted in hot weather and attracted rats, whose corpses were regularly evacuated each morning.
In frosty weather the leather flaps froze stiff and broke away and snow, instead of rats, got into the tube.
The system was so unreliable that it soon gave way to steam locomotives and the tube was dismantled after May 1847.
Brunel was attracted to the apparent advantages of the atmospheric principle so that he could take the South Devon Railway around the south coast from Exeter to Newton Abbot, where the gradients and tight curves were challenging to contemporary locomotives.
He was unconcerned when questioned about the wisdom of adapting the workings of a 1¾-mile branch line to a fifty-mile main line.
Daniel Gooch, the young locomotive engineer of the Great Western Railway, remarked, “I could not understand how Mr Brunel could be so misled. He had so much faith in his being able to improve it that he shut his eyes to the consequences of failure.”
The first atmospheric passenger trains between Exeter and Teignmouth ran on September 13th 1847 and to Newton Abbot on January 10th 1848. The entire service was operated by atmospheric propulsion from February 23rd 1848.
The new system was much admired for the lack of noise, smuts and smoke, and in the first few months barely 1% of atmospheric trains were more than ten minutes late. A 28-ton train could reach an average speed of 64mph over three miles.
On January 18th 1848, however, cold weather froze the leather and no trains ran until the afternoon. Increasingly, the leather flaps tore away from their fixings, allowing air leakages to diminish the partial vacuum. The underpowered steam pumping engines broke down repeatedly and coal consumption was excessive.
Everyone was aware that the London & Croydon Railway had given up on the atmospheric system in May 1847, and through the summer the directors and Brunel himself backpedalled.
The last atmospheric train ran on September 10th 1848.
The most visible reminder of the atmospheric railway is the pumping station alongside Starcross station which was used as a Methodist chapel from 1867 to 1958, while the boiler house became a coal store.
The entire building opened as a museum of the atmospheric railway in 1982 and is now the headquarters of the Starcross Fishing & Cruising Club.
Preparatory work for a road scheme has discovered the remains of a hitherto unsuspected fragment of the pumping station: http://www.bbc.co.uk/news/uk-england-devon-44099898.
The 36-page, A4 handbook for the 2017 Railways of Devon tour, with text, photographs, maps and a reading list, is available for purchase, price £10.00 including postage and packing. To order a copy, please click here or, if you prefer, send a cheque, payable to Mike Higginbottom, to 63 Vivian Road, Sheffield, S5 6WJ.