20/20 Did anyone do the math?

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  • Member since
    September 2003
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Posted by Overmod on Sunday, March 15, 2020 4:57 PM

The nominal 'absolute record' speed documented for a Y6 is a severe outlier, being pushed downhill into a sag by the train, with the engine one day out of the shop for a major. 

Th horsepower curves drawn for these locomotives show a radical falling-off of horsepower above 35 or so mph -- that does not indicate their 'top speed', only that the likelihood of them running fast on the level, let alone upgrade, with the train resistance that would have been assigned to get them to operate in the 'usual' speed range on that stretch of track, becomes increasingly implausible.  The great theoretical issue is the loss of effective balanced cylinder hp in the low-pressure engine at higher cyclic rpm with the valve gear set where it 'has to be', the effect being further magnified by effective loss of effective compression 'cushioning' of inertial mass 'as overbalanced' in the hinged engine.  Some of these effects could be overcome with judicious use of the 'booster valve' and I have argued that better proportional control of IP steam modulation and valve timing/duration could indeed allow one of these 2-8-8-2 chassis to work time-freight speed compound.

There s at least anecdotal evidence that N&W engineers tried to work these things fast in the frequent observation that -- net of all the great and justly-vaunted N&W maintenance, the things often sounded like accidents in a boiler factory running at any kind of speed on the road.  N&W proponents have attempted over the years to 'explain this away' by claiming that even though there was high mechanical noise, the excellent Virginia construction was showing no evidence of damage.  This is dubious from first principles alone.   However it's also no proof that good design and good maintenance weren't in fact in play.

I've said before that there are two things I'd like to be turned loose to play with: one is a Y6 chassis to be fitted with better balance and compliance and full IP modulation; the other being an A with the full Cincinnati service lightweight rods and Glaze-style balancing.  I personally have no doubt of the ability of the Y6 design to reach high speed if properly balanced and 'reheated' -- the limit being the inertial augment derived from the relatively heavy LP piston mass at given stroke expressing on the stability of the hinged forward engine.

  • Member since
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  • From: Henrico, VA
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Posted by Flintlock76 on Sunday, March 15, 2020 5:57 PM

For what it's worth...

My MTH Y6b will go so fast it'll fly off the train table and out the window if I let it!

Not the same thing, but just sayin'. 

Good little engines, those MTH O gauge products!

  • Member since
    April 2001
  • From: Roanoke, VA
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Posted by BigJim on Sunday, March 15, 2020 8:48 PM

Flintlock76
so, just how fast  could those Y6b's go? 


As I have quoted many times before from an engineer that ran them, "67 mph was about as fast as they would go, but, you really didn't want to run them over about 63 mph as after that they got pretty shakey".

And, this from someone who rode behind one..."after finishing spraying to Hagerstown, MD on the Shenandoah Division, our entire spray outfit was attached to the rear of a night train to Roanoke.  In those days, Class Y locos were known to run 55 - 60 mph on the upper end of the Valley, and ours that night was no exception.  The unsnubbed trucks on our car took the place of a motel vibrating bed that night."

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  • Member since
    January 2019
  • From: Henrico, VA
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Posted by Flintlock76 on Sunday, March 15, 2020 9:35 PM

Thanks Big Jim, now I know.  Whether it was a common occurance or not is immaterial to me, but knowing the capability was there when needed is good enough. 

N&W built some good stuff, didn't they?

  • Member since
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  • From: Roanoke, VA
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Posted by BigJim on Monday, March 16, 2020 8:43 AM

Yes, they did. They kept developing the Y class right up until the end. Long after other RRs had given up on the compound articulated.

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