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, >> > modeleng-request@xxxxxxxxxxxxx with the word >> "unsubscribe" in the subject >> line. >> > >> > >> >> > > > __________________________________________________ > Do You Yahoo!? > Tired of spam? Yahoo! Mail has the best spam protection around > http://mail.yahoo.com > MODEL ENGINEERING DISCUSSION LIST. > > To UNSUBSCRIBE from this list, send a blank email to, > modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject > line. MODEL ENGINEERING DISCUSSION LIST. To UNSUBSCRIBE from this list, send a blank email to, modeleng-request@xxxxxxxxxxxxx with the word "unsubscribe" in the subject line.