snifter valves

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BillCochrane
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snifter valves

Post by BillCochrane » Tue Dec 09, 2008 6:00 pm

Is it necessary for snifter valves to be installed on modern piston valve steam locomotives? I see them on lots of PRR engines but none on modern NYC and NKP locomotives.
Please help me.

Bill Cochrane

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Joe Tanski
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Post by Joe Tanski » Tue Dec 09, 2008 6:12 pm

Yes Bill They are required on piston valve engines. The whole purpose of the snifter valve is to allow air to be sucked into the cylinders when the Throttle is closed and the engine is running or drifting.If they did not have them the ash-used steam oil -cinders- would be sucked into the cylinders
and cause unwanted ware. On My new pacific I have 2 snifter valves on top of the cylinder block .(I put them in th 1/8 NPT valve timing port holes)
They also let me put 30 w oil into the valves and cylinders after a run to prevent rust and lock up when she sits
hope this helps
Joe

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BillCochrane
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snifter valves

Post by BillCochrane » Tue Dec 09, 2008 6:56 pm

Can't this also be done by the ports machined into the liners? I am stumped.
Any help is appreicated
Bill

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BillCochrane
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snifter valves

Post by BillCochrane » Tue Dec 09, 2008 7:04 pm

Joe
OK, now the question. Since I have the loco just about done what do I do now? Tear the front end apart again?
Bill C.

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Bill Shields
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Don't Panic!

Post by Bill Shields » Tue Dec 09, 2008 9:07 pm

You can put the valve anywhere in the steam line from the boiler to the valves...unfortunately, some level of tear-down is going to be needed.

Many british loco models had a T off the steam line, inside the smokebox, that went to a snifter that stuck it's nose out the side of the smokebox to 'fresh air'.

If you look at what Dave S. did on his Penna loco, you can see how the PRR handled it - a snifter on each steam line, just before it connects to the top of the cylinder casting. I don't know if Dave's PRR replicas are functional, but they sure look good.

Many options, only limited by imagination.

I like the idea of one snifter / cylinder - use them to dump oil in after running.

Image

On my Hudson, I made a combined fitting for snifter and oil entry.

Here you see it, between the inspection ports used to check valve position

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LivingLegend
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Post by LivingLegend » Tue Dec 09, 2008 9:44 pm

BillCochrane wrote:....Is it necessary for snifter valves to be installed on modern piston valve steam locomotives?
Yes. Especially on a coal fired loco.

BillCochrane wrote:....I see them on lots of PRR engines but none on modern NYC and NKP locomotives......
Look again..... They're there!

Both NYC and NKP (modern) loco's used them.

On top outside center of the steam chests. Right in front of the steam pipe. Same locoation as the valve in the photo Bill posted above.

LL
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Bill Shields
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NYC

Post by Bill Shields » Tue Dec 09, 2008 9:54 pm

which is why I put mine there...looks O-R-I-G-I-N-A-L

there was a time when I spent many hours duplicating the prototype.

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Trainman4602
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Post by Trainman4602 » Tue Dec 09, 2008 10:00 pm

Bill

That’s interesting that you should bring this subject up. Earlier tonight I was thinking of mentioning something about the snifter valve.


My locomotive has only one actual snifter valve. I think that’s all that is needed. Most of us have a “Tee” after the throttle valve. The tee is connected to the two branch pipes, there-fore that makes it all the same pipe. On the full-size the branch pipes are usually separated. They then would need two separate snifter valves in each steam line to the cylinders.


The actual snifter is under the scale snifter. The pictures show the throttle and the branch pipes the actual snifter and the scale snifter.
Attachments
throttle installed 3.jpg
Real snifter.jpg
Picture 145.jpg

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Bill Shields
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Piping

Post by Bill Shields » Wed Dec 10, 2008 6:29 am

Actually, unless you have 2 separate throttle valves for the cylinders, it is all 'one pipe' from a pressure (or vacuum) distribution standpoint and matters not where the line from the throttle to the cylinders is divided.

The pertinent question is the volume of the pipe from the snifter to the piston.

If the volume is too large, even with a snifter, some exhaust 'junk' will be sucked back, hence the use of multiple (usually 2) snifters, and usually very close to the cylinders.

It's a question of the amount of vacuum required to suck fresh air into the cylinder over a long vs. short distance. A pressure loss of a couple inches of water is important at this stage of the operation.

Since your volume is rather small, irrespective of the location of the T, your design will work just fine.

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Joe Tanski
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Post by Joe Tanski » Wed Dec 10, 2008 6:46 am

Bill :you can put it after the throttle, but by all means you must have it
vented to the outside of the smokebox to allow clean air to be sucked into
the cylinders.Is this for your mike or Eric's
Joe

10 Wheeler Rob
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RE Snifters, or lube ports.

Post by 10 Wheeler Rob » Wed Dec 10, 2008 9:00 am

M take is that because they can be used as lubrication points for adding oil lube for shut down and storage that makes putting one on each valve chest a good idea.

I have also seen on D-valve engines where the ports for snifters are pluged with a fake, and the vacumm brake function is provided with ball check type drain cocks valves. The pluge still provides a nice lube point into the valve chest.

Rob

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BillCochrane
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snifter valves

Post by BillCochrane » Wed Dec 10, 2008 10:05 am

Joe;
Eric's will be coal fired, mine will be oil. His is just about ready to roll. Thanks
all for the help and keep the solutions coming.
Bill C.

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