page_title: Steam spring
section_title: Steam springs
hierarchical_section_title: Steam spring / Steam springs
caption_attribution_description: Stephenson locomotive 1815
context_page_description: Steam springs or steam suspension are a form of suspension used for some early steam locomotives designed and built by George Stephenson. They were only briefly used and may have been used for fewer than ten locomotives.
context_section_description: At the time of these early locomotives there was not yet a way of forging an adequate steel spring to carry the weight of a locomotive. High quality steel had been available since Huntsman's crucible process, but it was still so expensive as to be regarded as 'a semi-precious metal'. It would be another forty years before Bessemer's converter made cheap bulk steel available. A similar problem affected safety valves, causing them to rely on dead weights or Hackworth's bulky stack of leaf springs, rather than the ubiquitous steel coil spring that would appear later.
  Stephenson's 'steam suspension' provided each wheel with its own 'steam spring'. Vertical cylinders were set into the base of the boiler, above each axle and offset in pairs to the sides. The chassis or frames of Stephenson's locomotives provided little structural strength, most of which came from the shell of the boiler. Inside each cylinder a piston carried the load of the axle and pressed upwards against steam pressure within the boiler. A piston of only a few inches in diameter was sufficient to balance the locomotive's weight. The axlebox bearings could slide vertically within hornblocks attached to the wooden frame beneath the boiler.
  Piston seals were a perennial problem at this time. Those for large stationary engines, working at low pressures, were sealed by a variety of methods including leather cup washers, pools of standing water and even a poultice of cow dung. As working pressures increased, which had been an essential part of turning the stationary steam engine into the mobile steam locomotive, demands on the piston seal increased further. Pistons were now mostly sealed by having oakum rope wrapped around them in a groove, often smeared with tallow. Keeping the rope seal moist, thus swollen, was recognised as an important factor in achieving a good seal. As the steam spring cylinders were in the lower part of the boiler, below the water line, it was expected that they would seal well. Despite this, they continued to give trouble with leakage and were eventually removed and replaced with iron or steel leaf springs. Wood in 1831 illustrates one of the Killingworth locomotives, now fitted with metal leaf springs and also coupling rods.
caption: 1877 drawing of a claimed '1815 Stephenson locomotive',[3] similar to The Duke but with flanged wheels, a plate chain and lacking the centre sprocket wheel.
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