[modeleng] Fw: Re: Lapping, pumps, etc was
- From: "John Browning" <jgb7573@xxxxxxxxxxx>
- To: modeleng@xxxxxxxxxxxxx
- Date: Tue, 28 Feb 2006 13:57:55 +0000
Guys,
Last week, there was an interesting discussion on axle pumps going on here.
One of the members of my club (Ickenhamd and District Society of Model
Engineers) is interested in communicating with the Phill who asked for the
following message to be posted to the group. If Phill could send me an
email off list (to jgb7573-AT-hotmail.com), I'll put them in touch.
Thanks,
John Browning
Chairman of Ickenham and District Society of Engineers
>
>
>
>
> >From: "Jesse Livingston" <fernj1@xxxxxxxxxxxxx>
> >Reply-To: modeleng@xxxxxxxxxxxxx
> >To: <modeleng@xxxxxxxxxxxxx>
> >Subject: [modeleng] Fw: Re: Lapping, pumps, etc was Date: Mon, 20 Feb
>2006
> >08:49:26 -0600
> >
> >
> >
> > > 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.
> > >
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