N & W Y5 Question

[wobblinwheel]

Does anybody know why the Norfolk and Western Y5 locomotive appeared to have TWO smoke stacks? There appears to be a smaller "stack" in front of the regular smoke stack. I think the Y5 series is the only one that looks like this. Anybody?

[BigJim]

That would be the Bradford Front End Throttle.

[Overmod]

I thought if I dug enough I could find it!

[wobblinwheel]

So it's not an "exhaust stack", but just a housing for the throttle mechanism? Or is it? Same thing on NYC's Hudsons? Why was it not used more on the Y's? Was it possibly "exhaust-assisted" to make it easier to operate? Just trying to figure this thing out, very interesting!

[Overmod]

In the case of the Y5s, it's a housing.  (Some places on the Web you have it described as a stack, but it isn't.)

The NYC Hudsons (and some others) have a small second stack for the booster exhaust.  This is only for steam.  Some railroads tried running the booster exhaust into the front-end arrangement, to utilize the exhaust for more induced draft.  This was often not a productive idea...

I don't recall if King of Jeffries went into any technical detail on the Bradford throttle.  I get the impression it was sold as an 'improvement' that could be relatively easily applied to a locomotive with a dome throttle to give the advantages of the front-end arrangement. To my knowledge it was not a 'servo' arrangement, like the ThrottleMaster, and it did not have a Wagner-type 'fluidic valve' providing proportional assisted motion from the differential in the steam pressure across the valve.

Unless I am mistaken, the later Y classes have American Multiple progressive poppet throttles. which have advantages over the Bradford arrangement.

[BigJim]

King/Dressler only mention that some Y5's were thus equipped.

The only thing in Jeffries book is that individual Y5's had what was thought to be experimental equipment. Only 2093 & 2100 - 2109 having the Bradford throttle. Not looking into this too deeply, I would suspect that those eleven engines got the American multiple valve throttles when they were rebuilt to the "Improved" specifications.