[modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was

  • From: "John Buckley" <jbuckley@xxxxxxxxxxxxxxxxx>
  • To: <modeleng@xxxxxxxxxxxxx>
  • Date: Tue, 21 Feb 2006 19:16:58 +1100

Loud and Clear in the land of Aus.
----- Original Message -----
From: "kenny" <kenny.macdougall@xxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Tuesday, February 21, 2006 1:12 AM
Subject: [modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was


> Hi just a test can anybody read this
> kenny
> ----- Original Message -----
> From: "Allen Messer" <al_messer@xxxxxxxxx>
> To: "modeleng" <modeleng@xxxxxxxxxxxxx>
> Sent: Monday, February 20, 2006 2:08 PM
> Subject: [modeleng] Fwd: Re: Re: Lapping, pumps, etc was
>
>
> >
> >
> > --- Phill Smith <steam@xxxxxxxxxxxxxx> wrote:
> >
> >>> Subject: Re: [modeleng] Re: Lapping, pumps, etc was
> >
> >> Date: Mon, 20 Feb 2006 13:25:25 +0800
> >>
> >> Gents,
> >>
> >> Modern fluid flow analysis has shown that the close
> >> fitting plunger in a
> >> bore causes more problems than it's worth, at other
> >> than low piston speeds.
> >> Optimal piston speed is below our "normal running
> >> speed" of our models. The
> >> greatest efficiency was found to be with a plunger
> >> operating in a free water
> >> space of at least twice the displaced volume of the
> >> plunger. The factors
> >> against the fitted plunger was due to the following
> >> factors;
> >>
> >> - Insufficient valve area due to limited space. To
> >> over come this, the
> >> valves had to have a high lift. This in turn
> >> resulted in water being pumped
> >> back down the suction pipe (and/or into cylinder
> >> from the discharge valve)
> >> for up to 30% of the compression stroke (this was
> >> worst on unsprung ball
> >> valves). Vapour pressures were entered into in the
> >> worst cases (suction
> >> pressures dropped low enough for the water to
> >> momentarily turn to steam).
> >>
> >> - Surge forces, due to rapid water flow in full
> >> cylinder, causing high
> >> friction losses and extenuating valve opening time.
> >>
> >>
> >> So, summing it all up.........
> >>
> >> You'd have a 1/2" plunger operating in a minimum
> >> 3/4" bore, with the "O"ring
> >> gland mounted as close to the water space as
> >> practical within the gland.
> >> This can be a screw in (replaceable)
> >> gland/guide/support. The guide is made
> >> from an extension of the gland which is fed with
> >> oil. Two small grooves are
> >> placed, longitudinally, on the bearing area of the
> >> plunger carry oil. One
> >> top and bottom. The large cylinder will accommodate
> >> larger valves
> >> (preferably of the disc type), on the end if
> >> possible (with flow axis in
> >> line with the plunger) with an area equal to the
> >> plunger diameter.
> >>
> >> This type of pump also allows for 2 different
> >> materials to be used for the
> >> plunger, and hence compatible bearing materials may
> >> be used for the gland
> >> and bearing area of the plunger. Especially since
> >> oil can be used as the
> >> lubricant.
> >>
> >>
> >> Cheers,
> >>
> >> Phill.
> >>
> >> PS     Could someone please post this to the
> >> "modeleng" discussion group, as
> >> I have not yet had time to sort out my "why I can't
> >> post anything (after a
> >> certain date) but receive fine" problem.
> >>
> >> ----- Original Message -----
> >> From: "alan stepney" <alan@xxxxxxxxxxxxxxxx>
> >> To: <modeleng@xxxxxxxxxxxxx>
> >> Sent: Monday, February 20, 2006 8:07 AM
> >> Subject: [modeleng] Re: Lapping, pumps, etc was
> >>
> >>
> >> > I have used stainless, and a reamed bore, and not
> >> had any problems so far.
> >> >
> >> > I leave a reasonable clearance between the bore
> >> and ram so that the
> >> packing
> >> > is the only thing making contact.
> >> > That should (??) prevent galling.
> >> >
> >> > A reamed bore seems to be sufficiently smooth to
> >> work OK and wear well.
> >> >
> >> > Alan
> >> >
> >> > MODEL ENGINEERING DISCUSSION LIST.
> >> >
> >> > To UNSUBSCRIBE from this list, send a blank email
> >> to,
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> >> line.
> >> >
> >> >
> >>
> >>
> >
> >
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>
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