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Astoneblower is arailwaytrack maintenance machine that automatically lifts and packs thesleepers with small gradeballast, which is blown under the sleepers to level thetrack.[1][2] An alternative to the use of aballast tamper, the totally self-contained machine levels track without the use of a large gang of workmen.
The Pneumatic Ballast Injection Machine was an experimental stoneblower tested byBritish Rail for the correction oftrack ballast andvertical geometry. It was built by Plasser GB, a division of the Austrian railway machinery companyPlasser & Theurer under contract to British Rail.[3]
A "frog" device which attached ahead of the machine reported measurements one metre apart of the altitude, relative to the starting point, of eachrail head, at eachsleeper, to an accuracy of 0.25 mm. Def"lectionindicators on each side reported height deviation at the 50 cm point between the two axles.Inclinometers on each side reported the angle from the horizontal, of the rail at that point. Electromagnetic sensors flagged the location of the steelPandrol clips which bind the rails to the sleepers.
An onboardDigital Equipment CorporationPDP-11 running theRT-11 real-time operating system andFORTRAN would then calculate the distance each sleeper end would need to be raised; this was recorded as a quantity of stone that would hold the sleeper end at the new level.
At each pair of sleepers, the machine lifted the track 50 mm and forced eight giant "hypodermic needle" points down to the level of the resulting temporary cavity below the sleepers. FourArchimedes screws dispensed a measured quantity of gravel into the needles, and a jet of high pressure air at the back of the needle tip blew the stones into the cavity.
Expected results were not achieved in practice,[4][5] and British Rail continued to use the ballast tamper.
By 1999, stoneblowers were in use throughout the UK rail network.[6]
Stoneblowers were manufactured by Harsco Track Technologies in conjunction with Network Rail. Although these machines have been shown to extend the track maintenance cycle, the inserted material can interfere with future ballast tamping.[7]
Stoneblowers continue to be used by some rail lines in the UK,[8] including by Network Rail.[9]
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