Thank you very much to cprted, benburch and Pete. I appreciate that you took the time to reply to my question.
Nick
Lubrication in the form of a tallow was carried by the steam to lubricate the valve and pistons/packings. The snifter valve was also used for when the locomotive was light stationary. It prevented the steam to get past a leaking valve and cause the loco to move by itself. Steam leaking into a cylinder would over power the independent brake. With better lubrication in latter years the wear from drifting/coasting was minimal. Often times pushers when cut off would just coast back down the hill and wait for the next train.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
As I understand it the issue is that you are admitting no steam so when the cylinder works it creates a vacuum and will, when the exhaust stroke happens, suck in cinders and oil and such from the smoke box.
I recall this is also called a Wagner valve.
Note that in spite of the obvious issues for the longevity of the locomotive, some hoggers used this as a sort of dynamic brake when coming down grade.
Yes, the drifting or snifter valves prevents the pistons from forming a vacuum in the cylinders when steam isn't being applied.
Sometime ago I read or heard that letting a steam locomotive coast along using its own momentum, throttle off, was not a good idea. Why was this?
I was reminded of this while reading John P. Hankey’s, excellent article about roundhouses in the March, 2010 issue of TRAINS magazine. A picture on page 31 shows a worker adjusting the “drifting valve” on a locomotive mounted above the cylinder assembly.
Did this valve have something to do with allowing the locomotive to coast or drift?
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