[modeleng] Re: Automatic drain cocks
- From: Jerry Kimberlin <kimberln@xxxxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Mon, 19 Nov 2007 15:52:41 -0800
John Pagett wrote:
> Guys,
>
> Does anybody know how automatic drain cocks work? I know GW locos had
> pressure relief valves on the cylinders, but I didn't think they were the
> same thing.
Automatic drain cocks are just a spring loaded ball against a hole seat
leading to each end of the cylinder. When the pressure in the cylinder
overcomes the spring tension, the pressure is relieved. Usually the
spring is stronger than the steam pressure, so only water that is pushed
by the piston is strong enough to compress the spring and get past the
ball to the drain. There are other types of drain cocks that use steam
pressure to close a hole to the cylinder using a piston, ball, or teflon
diaphragm. They are not considered automatic, however.
JerryK
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