[N&W] Steam hard on the track

[nw-mailing-list at nwhs.org]

Jerry Crosson comments on Charlie Long's question:

The following is based on what I remember and what I've read;

Steam locomotives did cause some rail damage, via the transfer of the 
vertical component of piston thrust thru the drivers onto the rail.  This 
effect was partly reduced by counterweighting each driver, and by more 
sophisticated cross-counterbalancing of the entire drive wheel unit.

Post WW - I locos were improved over earlier locos; technology provided 
better tracking quality and protection for the rails as loco weight and 
speed increased.  The performances of UP's Challengers and N & W's Class A 
would not have been possible without improvements to loco
suspension and balancing.

Rail damage could be further decreased by using 3 or 4 cylinders, as was 
commonly done in England and France but which was little used in this 
country.  Dividing power input into more frequent, but lesser force blows 
per revolution meant less balancing via counterweights; hence less vertical 
pounding.

As to long rigid wheelbase being a factor - most modern main line steamers 
were provided with some form of lateral play device for the leading 
drivers; some also had flangeless center drivers.

First generation diesels damaged the rails in a different manner.  The 
powered axles are not coupled - differential rotating speeds, even slight, 
could burn the railheads.  It seems to me this would be more true at start 
and at slow speeds.  More recent diesel controls have sensors to minimize 
differences in axle rotating speeds.

My conclusion has been that rail damage was little or no factor in the 
decision to replace steam power with diesel power.

Jerry Crosson