Tuesday, August 4, 2009

Regulating track ballast

It's not a form of government control but an essential component in good railway track. Track ballast is part of the track structure. It provides supports to the ties from below and holds the ties and rail in place by resisting the moving - or dynamic - forces caused by a passing train. In a curve, the train tries to push the curve outwards. On tangent track, any rocking and rolling of the cars tries to force the track to one side or the other. When braking down a descending a grade, a train tries to push the track down the hill. A sufficient amount of properly placed ballast resists these forces and holds the track in position.

Ballast has existed since the first colliery railroad some 200 years ago. Historically, it was often little more than locally-mined sand and gravel, and in many instances was no better than the best local native material. That meant it could have been sand, or even just dirt. Today, however, most railroads including the Northwest Railway Museum have graduated to crushed rock - meaning fully-fractured faces with no round edges - because it holds the track level and within lateral alignment ("in profile") far better than sand or gravel and helps promote good drainage. But crushed rock is heavy and difficult to shovel so working with it by hand is very labor intensive. During the labor shortages of WW II, that gave a cleaver railroad contractor in Alabama the incentive to develop a better way. Royce Kershaw designed and built the first ballast regulator by mounting a set of railroad push car wheels on a old Ford pickup and attaching a plow blade to the front.

A ballast regulator in its simplest form is a plow blade that spreads ballast evenly along the track, often right after it is dumped along the track by a rail car. In a more complex configuration, it uses a series of plow blades to transfer ballast from one side of the track to the center, or even from one side of the track to the other. Today, many "regulators" have also added a broom attachment that is used to sweep the excess rock off the top of the ties and spread it along the sides of the track.

The Museum holds a classic ballast regulator in its collection. This 1963-built Kershaw was used on the Great Northern Railway and successor Burlington Northern in Stevens Pass. Powered by a Detroit 3-53 diesel engine, it has been undergoing rehabilitation in the Museum's Conservation and Restoration Center. Leading the effort is Brandon C. with active participation from Rich W., Dan C., Ian, Earl W. and Dale C. Several bearings have been reworked, some missing and damaged hardware has been replaced, sheet metal panels have been straightened and cleaned, cracks in the plows have been welded, and everything has been painted. With a few more weeks of work remaining, this ballast regulator will be fully functional; more will be posted about the regulator in the coming weeks.

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