Two Rod and Valve Gear Questions

[NW Mailing List]

The ratio between the distance of the main pin from the axle center varied from engine design to engine design.  It would be different from, say, the Y-6 and the J – both engines had 32-inch strokes but a foot difference in driver diameters (assuming new tires).  

The normal practice in American railroading was right-hand lead.  The PRR was the notable exception to this; they used left-hand lead.  It was known that the side that had the lead pounded the track more than the other; one theory has it that PRR wanted the left-hand side to pound the roadbed harder because ot a preponderance of multiple-track railroading; the left side of the roadbed would be stronger.  The quarter was the standard for two-cylinder locomotives, assuring the most even distribution of torque during the rotation of the wheel.  Three-cylinder locomotives typically used a 120-degree ratio instead of a quarter.  The exception to this is the Baldwin 60000 three-cylinder 4-10-2 displayed at the Franklin Institute in Philly.  It’s drivers are quartered, but the third cylinder is 135 degrees from both the outer crankpins.  

Hope this helps.

EdKing


From: NW Mailing List 
Sent: Monday, August 06, 2018 6:16 AM
To: N&W Mailing List 
Subject: Two Rod and Valve Gear Questions



Hopefully there will be some talent left around which can give an answer to these two humble little questions...



(1)  Is there always a mathematical ratio of 2:1 between (a) the distance from center of axle to center of main driving crank pin, on the one hand,  and (b) the length of the stroke of the piston, on the other hand?  (Prima facie, this sounds like a really, really dumb question... sorry.)



(2)  In quartering drivers on axles, how far in degrees is one driver advanced beyond perfect quarter, to insure that the engine will never be caught on dead-center?  (And I believe N&W used right-hand lead, contrary to most American practice, did they not?  If so, I wonder where that practice came from?)




--  abram burnett, 
(who should probably just stick to turnip farming...)

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