[modeleng] Re: Drain Cocks
- From: The Sheppard Residence <psbr20252@xxxxxxxxxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Thu, 06 Nov 2008 21:03:28 +0000
John, Peter & Jeff,
You are of course quite right, they will need to close off steam at
boiler pressure. My excuse is that it was late last night I posed the
question!
Jeff, yes it does look at bit basic, but then that's the level of my
workmanship! I have the shaft made and have cut the O-ring grooves to
suit a box of O-rings I had on the bench!
I have the brass hex drilled and the shaft with the O-rings on it, it
seems to fit reasonably well. I agree though that there will be a gap
between the outer diameter of the shaft and the inner diameter of the
hex. To reduce the amount of steam in there I plan to use a small hole
(which most drain cocks seem to do).
Before I get too far with it I want to put some compressed air in it and
see how well it seals at various pressures. Mind you, when you compare
it against Tinkerbell at the moment, any form of seal will be an
improvement :-)
Cheers
Peter
John Pagett wrote:
> Peter,
>
> The answer depends on whether you've got slide valves or piston valves.
>
> If it's slide valves, then they shouldn't see any more pressure than the
> steamchest pressure, but with piston valves it is possible for water to be
> trapped with nowhere to go as the piston approaches one of the dead centres.
> The pressure attained depends on lots of things, wheel/rail grip, train
> momentum etc, but can be enough on a full sized loco to remove the cylinder
> cover and part of the cylinder with it.
>
> JohnP
> ----- Original Message -----
> From: "The Sheppard Residence" <psbr20252@xxxxxxxxxxxxxxxx>
> To: <modeleng@xxxxxxxxxxxxx>
> Sent: Wednesday, November 05, 2008 10:06 PM
> 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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