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

From: "kenny" <kenny.macdougall@xxxxxxxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Date: Mon, 20 Feb 2006 16:00:21 -0000
 Hi Allan many for getting back to me from the Misy Isle Minuture Railway on 
the sunny Isle of Skye
kenny


----- Original Message ----- 
From: "Allen Messer" <al_messer@xxxxxxxxx>
To: <modeleng@xxxxxxxxxxxxx>
Sent: Monday, February 20, 2006 2:16 PM
Subject: [modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was


> Kenney me lad, I read you loud and clear here in the
> frozen South.
>
> Al Messer
>
> --- kenny <kenny.macdougall@xxxxxxxxxxxxxx> wrote:
>
>> 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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>> >> "unsubscribe" in the subject
>> >> line.
>> >> >
>> >> >
>> >>
>> >>
>> >
>> >
>> > __________________________________________________
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>
>
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References:
- [modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was
  - From: Allen Messer
[modeleng] Re: Fwd: Re: Re: Lapping, pumps, etc was

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