Engine "Slippery-ness"

[NW Mailing List]

I may get zapped on this by those with first-hand experience, but IMO factor of adhesion is not the ruling factor in predicting a locomotive's propensity to slip.

N&W operated locomotives with FA's far less than the so-called magic number of 4.0 (which is an average number, not an absolute figure).  As a company, it didn't seem to have any problems keeping the A, J and Y5-Y6 classes on their feet, so-to speak. It's always sounded to me as if locomotive control is a general mixture of handling (engineer skill), track condition (geometry and maintenance), rail condition (clean, wet, icy, etc), locomotive condition (maintenance, preparation) and likely many other factors.  Let any one of these go to pot, and you may end up with a hard-handle-locomotive.  N&W seemed to have these variables under daily control and was therefore able to use locomotives that would be slippery based solely on numerical indicators.  Based on research, it seems as if engineer skill is a big factor overall.  There are stories relating how the same locomotive was flogged over a division with considerable complaining by one engineer.  On the
 next division (same train assignment), the same locomotive exhibited no deficiencies because of more skilled operation.

I'm as interested as Mark in hearing what those with real-world experience can add to this.  I'm just an observer and number cruncher.

Dave Stephenson


--- On Tue, 9/15/09, NW Mailing List <nw-mailing-list at nwhs.org> wrote:


> From: NW Mailing List <nw-mailing-list at nwhs.org>

> Subject: Engine "Slippery-ness"

> To: "NW Mailing List" <nw-mailing-list at nwhs.org>

> Date: Tuesday, September 15, 2009, 5:41 PM



> I know factor of adhesion is the ruling factor of slippery-ness in

> locomotives.   How much of this feature was because of the engineers handling of the engine?

> 

> I see on the may videotapes and DVD's the society sells the Y6b's slipping a front engine or an A class slipping a rear engine and I'm sure the engineer is right on the throttle to back it off  a notch or 2. The engines of lesser boiler pressure are not so slippery but thats due to less push on the cylinders.

> 

> How touchy was the handling of the power right at the theoretical limits of their design?

> 

> I know of lots of things which limit some engines, like back pressure and counterweight limitations because of wheel diameter, but these factors don't interfere with the slipperiness.

> 

> I'm very interested in what it was like to be the engineer or fireman on several N&W Locomotives. Pushers, Mine runs, and time freights all interest me.

> 

> I model the 1930's for the look of the engines.  The K3's and Z1's are wonderful. My favorite is the M2c and M class engines.

> 

> I may end up designing a fleet of them based on my Sunset brass one.

> 

> 

> Mark Lindsey

> y3a at earthlink.net

>