snifter valves

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JKreider
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Post by JKreider » Wed Dec 10, 2008 10:48 am

Installation of drifting valves on modern piston valve locomotives was not a universal application. Some locomotives, including the NKP Berkshires, were never equipped with them.
NKP’s operating practice dictated open throttle running that is, using the brake and cutoff to operate a train or locomotive under heavier draft conditions. Of course the throttle was opened and closed shuttling around the yards or coming off a turntable. Under those conditions, of course, creating a vacuum in the cylinders was not a problem.
In a model it's a good idea. Some of the model Berkshire builders have installed drifting valves per ideas as suggested here on this thread with good results, and others have operated without them, even on coal, with no problems.

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LVRR2095
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Post by LVRR2095 » Wed Dec 10, 2008 1:57 pm

It shows the influence of the British Live Steam hobby on us, that here in N. America, most folks seem to use the British terminology..."snifting" valve. On full size railroads here in N. America they were always "Drifting" valves. Similarly I see many N. American live steamers using the term "Clack Valve" which was never used here. They were always "Check Valves." This is just an observation, not a criticism.
Keith

B&OBob
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snifter valves

Post by B&OBob » Wed Dec 10, 2008 2:21 pm

LBSC often had his snifting valve pass through the top of the smokebox and screwed into the cold end superheater header. That has the significant advantage of drawing-in cold air through the superheater when the throttle is closed and the engine is drifting. That's what I have on my 2.5" gauge Tenwheeler with piston valves.

BTW, it pays to have a tapered wood plug that you can drop through the stack and push into the blast nozzle before cleaning cinders out of the smokebox. Without doing that there is a good chance some grit will get into exhaust passages and possibly be sucked into the cylinders later while the engine is being pushed from the steaming bay to storage or van/trailer.

Re Clack Valves: When did "valve" get added to the term; they used to simply be called "Clacks" in early British writing. Not that it matters.

Bob

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BillCochrane
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snifter valves

Post by BillCochrane » Wed Dec 10, 2008 5:39 pm

With the replies received so far I will not apply snifters to the loco I am building. It seems that by appling the cutoff valve and the throttle as done on the full size modern steam engines little or no debris will be entering the piston valves. I will use the wooden plug trick as advised by B&O Bob when cleaning out the smoke box. Thanks again to all that replied off line or as part of this forum.
Thanks all,
Bill Cochrane

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makinsmoke
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Re: snifter valves

Post by makinsmoke » Sat May 05, 2018 8:10 am

Ressurecting an old thread.

The prototype ten wheeler I’m modeling has slide valves and what appear to be ball valves
in the front of the steam chests where the snifter, ahem drifting valves go.

Can we explain the pros and cons of this installation versus a drifting valve, albeit on a slide valve loco?

Thanks,
Brian

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Builder01
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Re: snifter valves

Post by Builder01 » Sat May 05, 2018 9:29 am

On my locomotive, with slide valves, the snifter valve is piped to the wet header of the super heater. This allows fresh air into the super heater when the throttle is closed. This helps the super heater from getting too hot with no steam flowing through it.
DSCN1448 - reduced.jpg
On the right, there is a pipe that curves down from the wet heater to the snifting valve. The snifter valve itself, is the fitting that connects the pipe to the side of the smoke box. Fresh air is drawn in from the outside through this fitting. If you do not have a super heater, the snifting valve(s) could probably be piped anywhere between the throttle and the steam chests. Mounting them directly on the chests is certainly a way to do this, although, you would need two snifters instead of one.

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NP317
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Re: snifter valves

Post by NP317 » Sat May 05, 2018 9:34 am

Prototype installation on the front of the steam chests is easy to install and maintain, and does the job.
Mine have been operating there with no problems, since the locomotive was built.
Here's a picture of the scale valves made by Keith Sternberg (WA State) for his Allen Ten Wheeler.
~RN
VacValve2.jpg

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Fender
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Re:

Post by Fender » Sat May 05, 2018 11:49 am

JKreider wrote:
Wed Dec 10, 2008 10:48 am
Installation of drifting valves on modern piston valve locomotives was not a universal application. Some locomotives, including the NKP Berkshires, were never equipped with them.
NKP’s operating practice dictated open throttle running....
I believe this was typical of “water level” lines, to always “work steam” when running. I have a recording of an Illinois Central mikado pulling into a siding for another train to pass, and the engineer is working steam until the loco comes to a stop. Obviously this might not be possible on a line with mountain grades.
Dan Watson

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makinsmoke
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Re: snifter valves

Post by makinsmoke » Sun May 06, 2018 7:27 am

Yes, front of the valve block is where I’ve seen them most.

I did find another thread where glove not ball valves were mentioned on slide valve locos.

Mainly used cracking the globe valve while sitting, to keep the loco from crawling off with a leaking throttle valve.

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Builder01
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Re: snifter valves

Post by Builder01 » Sun May 06, 2018 7:41 am

While sitting, if you put the valve gear in mid position, usually the locomotive will not move. (if the valves are set correctly)

If you have manually operated globe valves to bleed steam from the chests to allow for a leaky throttle, then you have to close the valves before starting? I guess this could be done, but, what a strange to operate. You could also just open the cylinder drain cocks if your throttle is leaky.

David

jlakes85
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Re: snifter valves

Post by jlakes85 » Tue Aug 14, 2018 7:02 am

Hi All,

Which manufacturers are producing snifter valves currently? Thanks again.

-jlakes85

hoppercar
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Re: snifter valves

Post by hoppercar » Tue Aug 14, 2018 8:23 am

I built the rrsc mikado, it has piston valves, I had rrsc, and then railroad warehouse both tell me this engine does not need shifter valves?....I have never figured out why ??

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