Nashville Engine's Piston Rods

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  • Member since
    May, 2018
  • 4 posts
Nashville Engine's Piston Rods
Posted by DevinCamary on Monday, May 14, 2018 12:27 AM

So i am confused on the one famous engine that pulled the Lincoln Funeral train. I noticed it has two valve rods going into the steam chest. One of the rods is to the gab valve gears and the other a lever to the cab. But the one that ISN'T going to the gab valve gear, i think that helps cut off steam to perserve it. But... how does that work? Because I got no clue. 

https://imgur.com/a/BzPQMio

https://imgur.com/FxNAeyY

 

I noticed this is a close thing to what I am seeing... but this particular Engine doesnt seem to have this sort of lay out and i am still confused. 

https://imgur.com/O3rJdGT

 

If anyone can better describe what the second valve rod for the Nashville does exactly, i would be VERY happy.

  • Member since
    September, 2003
  • 5,602 posts
Posted by Overmod on Monday, May 14, 2018 1:02 PM

Some of the mystery is discussed here, I think.

While it is possible to build a gab-gear/hook-motion engine with the effect of variable cutoff, it would not be easy to operate it ... certainly not with fine control or frequent adjustment.  So the use of 'riding cutoff' is adopted to give some of the advantages of link motion.  On Nashville, the lower rod works the conventional valve, probably full-stroke, and the upper rod and its linkage gives the cutoff.

Note the difference between this and the use of something like Cuyahoga Cut-Off on a link-motion engine, where one of the effects is similar to long-lap valves by providing the cutoff action cleanly and relatively quickly with large port opening.  This limits "wiredrawing"effects in saturated steam at high cyclic rpm, among other things.

  • Member since
    May, 2018
  • 4 posts
Posted by DevinCamary on Monday, May 14, 2018 9:11 PM

Ah, alrighty. I will take a look at that now.

 

And that is pretty interesting. Yeah i know the lower pin is for the valve and the upper one for cut off, but i didnt know how the cut off for this engine works. Bc if it's just a solid thing like in the other diagram i sent then one of the steam entry ways will have full steam while the other doesnt. if there is a diagram to explain how this particular cut off works i would be VERY happy

 

and why i ask is bc i am currently building a 3d model off this engine

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