[modeleng] Re: Fw: Re: Lapping, pumps, etc was
- From: "Pendragon" <idpriest@xxxxxxxxxxxxxxxx>
- To: <modeleng@xxxxxxxxxxxxx>
- Date: Mon, 20 Feb 2006 18:26:38 -0000
Gents,
I'm sure LBSC wrote the same sort of thing many years ago and without =
the
benefit of modern science, sure does show the old fella knew his onions.
Regards IDP
"Life should NOT be a journey to the grave with the intention of =
arriving
safely in an attractive and well preserved body, but rather to skid in
sideways, Champagne in one hand - strawberries in the other,=20
body thoroughly used up, totally worn out and screaming WOO HOO - What a
Ride!"=20
=20
"Never drive faster than your gaurdian angel can fly"
=20
Priest & Sons Model Engineers
http://www.kinvermes.pwp.blueyonder.co.uk/p1.htm
-----Original Message-----
From: modeleng-bounce@xxxxxxxxxxxxx =
[mailto:modeleng-bounce@xxxxxxxxxxxxx]
On Behalf Of Jesse Livingston
Sent: 20 February 2006 14:49
To: modeleng@xxxxxxxxxxxxx
Subject: [modeleng] Fw: Re: Lapping, pumps, etc was=20
> 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=20
> speeds. Optimal piston speed is below our "normal running speed" of=20
> 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=20
> pumped back down the suction pipe (and/or into cylinder from the=20
> discharge valve) for up to 30% of the compression stroke (this was=20
> worst on unsprung ball valves). Vapour pressures were entered into in=20
> 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=20
> 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=20
> 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,=20
> as
> I have not yet had time to sort out my "why I can't post anything=20
> (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=20
>> well.
>>
>> Alan
>>
>> MODEL ENGINEERING DISCUSSION LIST.
>>
>> To UNSUBSCRIBE from this list, send a blank email to,=20
>> modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the=20
>> subject
> line.
>>
>>
>=20
MODEL ENGINEERING DISCUSSION LIST.
To UNSUBSCRIBE from this list, send a blank email to,=20
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