The Stoneblower is a machine developed specifically as an alternative to traditional tamping methods for the restoration of track's vertical and lateral alignment.

The machine utilises a process which pneumatically injects ballast under the tie to achieve track positioning to an accuracy of 1.0mm without disturbing the pre-existing compacted foundation.
On-board computers use the data collected during the measurement process to determine the profile of the track and calculate the lift, slew and stone quantity for each tie. The design uses a pre-selected track quality level to minimise lifts and the quantity of ballast required.
The machine moves down the track, in the opposite direction to measurement, treating each selected pair of ties simultaneously. At the completion of maintenance the machine produces a record of pre and post-treatment track quality. The resultant condition of the track is generally suitable for immediate unrestricted line speeds.
The Stoneblower's track design system targets only sections that require rectification and does not treat track with acceptable pre-maintenance quality. For this mode of operation, production rates can exceed 900metres per hour with rates in typical stoneblown sections averaging 440metres per hour.
The graph below shows the improvement in durability for the stoneblowing process.
This figure was compiled from the United Kingdom track data and shows the increase in time between maintenance cycles varying from five-fold improvement for track requiring tamping every six months to a two-fold improvement for track requiring tamping every thirty months. m

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Harsco Track Technologies is based in Cayce-West Columbia, SC, USA. www.harscotrack.com