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Re: PE-Caps, tests, and some questions
Tesla List wrote:
>
> Hi Chris and all,
> A couple of sites to check out for all you 'vacuum heads' out there. For
> technology and experiments try
> <www.eskimo-dot-com/~billb/amateur/belljar.html>. For pumps and parts go to
> <www.duniway-dot-com/>
> Chris, I found your pump in a 1982 scientific catalog. Looks like you
> found a good pump if it's in good working order. Specs as follows; Mfr.#
> 8811B (B for 115 Volt/60 Hz model), direct drive, two stage, 1/3 hp.
> Free air displacement=100 Liters/min. (3.5 C.F.M.). Vacuum=.6 micron.
> Oil capacity=2 liters. Temp. rise=31 deg. C. Has internal oil pump,
> anti-suckback valve, and vented exhaust. Weight=54 lbs. 1982 price= $
> 862.14. Today's price probably at least twice that or more. NOTE: use
> only the proper low vapor pressure oil for vacuum pumps, NEVER use motor
> oil or any thing else except the proper oil for any vacum pump. For your
> direct drive Welch, W.W.Grainger sells 1 liter bottles for $10.40 ea.
> (Grainger stock #6D754)............. Good luck with those caps!
> Tony Greer
>
> ---------------------------------------------------------------
>
> Subject: PE-Caps, tests, and some questions
> Resent-Date: Wed, 21 Apr 1999 18:01:29 -0600
> Resent-From: tesla-at-pupman-dot-com
> Date: Wed, 21 Apr 1999 11:51:59 -0600
> From: Tesla List <tesla-at-pupman-dot-com>
> To: tesla-at-pupman-dot-com
>
> Original Poster: Chris Tominkson <internetinbox-at-yahoo-dot-com>
>
> The other day I tested some Aluminum
> Flashing/Polyethelyne caps and I realized that the Al
> flashing is really hard to roll, and also the
> recomended 90 Mils of PE is way too much to roll with
> Al flashing, and I had three other people helping me.
>
> I calculated the caps to be .005 uF, but when rolled
> they were way too low (like 7 or 8 times too low),
> because of misaligned plates, air gaps, and we were
> just unable to make them work. So we made the
> polyethelyne 12 Mils thick, with the same plates, and
> got a .0198 uF off the fluke, thats huge! And those
> were very easy to roll, we probably could have got
> even more with Aluminum Foil, since it could be rolled
> tighter.
>
> But why I wrote this post is this: A lot (6+) of
> smaller capacitors would be a lot easier to create,
> roll, and handle than one or two big ones.
>
> Now the question:
> I just bought a Vacuum Pump, Sargent Welch Direct
> Torr, model 8811. I was wondering if anybody has any
> specs for this pump, or any kind of information about
> it. I bought this pump for the rolled caps among other
> things, and I have no expierience with vacuum pumps.
> Also when does water boil in Torrs, and does anybody
> know a good book or reference on vacuum pumps.
>
Vacuum stuff:
Roy Schmaus' Vacuum Page http://www.ee.ualberta.ca/~schmaus/vac.html
for the water boiling question. You need a "steam table" which gives the
boiling point at various pressures. A short excerpt:
T (deg C) Pressure (mbar/hPa)
.01 6.11
10 12.28
15 17.05
20 23.4
25 31.7
30 42.5
36 59.5
Convert hPa to Torr >>> Torr = 760/1013 * hPa
To convert pressures to equivalent altitude, remember that the pressure
is halved every 18000 ft, (i.e. at 18000 ft, air pressure is about 500
hPa, at 36000, about 250 hPa, etc.) so 23.4 hPa is about 100,000 ft.