[modeleng] Re: Drain Cocks
- From: Dave Beaman <dave.beaman@xxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Thu, 6 Nov 2008 22:08:04 -0000
The most that a drain cock will be asked to do is empty a cylinder full...
Amd I ,mean full after a test.... of water. That is the function of a drain
cock, to clear the cylinder of water. As long as th "tap" can get water out,
you should be ok. A friend of mine did explain ... with equations and
mathermatics, how the forces on a cylinder cover could break it and or bend
motion... see anyone who worked on 5000 on the SVR, combination lever..
For our size engines, the cocks are not as critical, indeed, someone wrote
in sme years ago that cocks were not required for 5", just keep away from
the chimney when the engine is a little cold or boiler a little full!!!
Dave.
----- Original Message -----
From: "Jeff D" <jeffdayman@xxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Thursday, November 06, 2008 12:18 PM
Subject: [modeleng] Re: Drain Cocks
>I agree, the cocks should be made to take BP + a safety factor.
>
> I too saw the article in EIM, but I am not clear how the individual ports
> are sealed. I see there is an o-ring between each of the 4 ports, but
> apparently no seal is used around each port hole (at least it is not
> visible). To me, this would leak at least a bit, as there has to be some
> clearance from valve dia to block bore diameter, whether the port is
> aligned
> to the outlet or turned 90 degrees. With tapered drain cocks, the taper
> takes up the clearance mentioned and so it seals without a port o-ring or
> packing.
> To seal the straight bodied valves, I would think an o-ring would be
> needed
> around the ports also, but this would be a saddle shaped groove and quite
> hard to machine, and the o-rings may cut where they cross the port edge.
>
> Did I miss something? is there a floating PTFE bit or other seal?
>
> Cheers Jeff Dayman
>
>
>
>
>>From: "Peter Beevers" <peter@xxxxxxxxxxxxxx>
>>Reply-To: modeleng@xxxxxxxxxxxxx
>>To: <modeleng@xxxxxxxxxxxxx>
>>Subject: [modeleng] Re: Drain Cocks
>>Date: Thu, 6 Nov 2008 06:59:37 -0000
>>
>>Peter,
>>
>>Hmm, they will have to deal with steam at near boiler pressure - when they
>>are closed, and steam is admitted into the cylinder on the power stroke,
>>they will have to stay closed despite that pressure. Worst case, they may
>>have to resist (for very short periods, when starting), almost 100% boiler
>>pressure, depending on the efficiency of your steam circuit.
>>
>>In general, the pressure will be less - while running probably no more
>>that
>>30-40 psi.
>>
>>Hope this helps
>>
>>Peter
>>----- Original Message -----
>>From: "The Sheppard Residence" <psbr20252@xxxxxxxxxxxxxxxx>
>>To: <modeleng@xxxxxxxxxxxxx>
>>Sent: 05 November 2008 22:06
>>Subject: [modeleng] Drain Cocks
>>
>>
>>There was a very interesting article in the 7.25" news last time (I
>>think) about a "centralised" drain cock system which I am currently
>>building. There were no drawings, just a picture of the components and
>>the assembled item.
>>
>>One thing I would like to do is test mine before I install it on the
>>locomotive, the question is, what sort of pressure do the drain cocks
>>have to cope with?
>>
>>It obviously isn't boiler pressure as by the time that they are in use
>>the steam has done its work and it is being exhausted, but there must
>>still be some pressure there.
>>
>>Does anybody have any idea how much (so I can set the air compressor
>>accordingly).
>>
>>Cheers
>>
>>Peter
>>
>>
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>>
>>
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>
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