Ignoring the day job vacuum pumps, I have a Gast pump I use at home,
Let me weigh in on a few things,
Degassing, I use (again at home), a menudo pot (big aluminum pot, they
cost around 30-40$ plus need to add a plexiglass lid so you can see
through and a rubber gasket (needs to be thick). For this i want a
high volume flow, so I can draw down the pot. 25 inch Hg minimum. Plus
if you want to get very good degas resin add a degassing agent (small
percentage siloxane, or BYK-501) makes a very big difference. This is
what we do at the day job. Bumping the mix, draw vacuum, quickly
release and then draw vacuum again before letting it sit works well, for
that you need a vacuum pump with some volume.Cheep vacuum gauge works.
You can buy degassinng kits from ebay pot with lid and pump.
Vacuum Bagging, you need t leave the vacuum on during the cure to get
the best properties. ust bagging a part (food sealer only gets you a
little way, a pump running during cure and a breather in the bag will
get you full 14psi pressure on the lamiante. Always use a resin trap,
For home and the day job we use gallon pickle jars, with a rubber cap.
The hose TO the vacuum bag runs to near the bottom of he jar the one
FROM THE PUMP runs to the top of the jar. That way if you suck resin in
is doesnt get into the pump. You can reuse the jars just let the resin
cure in the bottom and leave it. Again 25in Hg minimum. Cheep vacuum
gauge works.
Fora pressure chamber you don't need nearly the depth of vacuum that
you need for degassing or vacuum bagging. The trick is to regulate the
vacuum for this. A cheep vacuum accumulator, and a needle valve to a
bell jar (or use a pickle jar). An empty helium tank (the disposable
ones for filling up balloons), an LP tank, or an air tank from Harbor
Freight ($25 before the coupon, and there is always a coupon). Draw
vacuum on the tank to a reasonably low level, have the tank connected to
a jar, allow open the needle valve slowly to 'simulate launch' close at
apogee, open another needle valve to let the pressure return to earth.
A chart converting altitude to pressure is at
https://www.sensorsone.com/altitude-pressure-units-conversion/
On 4/25/2020 9:48 AM, Lee Buchok (Redacted sender hyflynboy for DMARC)
wrote:
Can’t remember exactly, it’s been awhile. I think it may have been around 4 to 5 thousand ft. I was using it only for functionality checks on an altimeter. I remember not being able to completely seal the bell jar connections.
Sent from my iPad
On Apr 24, 2020, at 12:40 PM, Cris Erving <cris.erving@xxxxxxxxxxx <mailto:cris.erving@xxxxxxxxxxx>> wrote:
How much "altitude" can you get with it? I got one of those two during the 25% BF sale... I haven't had the time to rig up a test jar yet.
Eggtimer Cris
------------------------------------------------------------------------
*From:* roc-chat-bounce@xxxxxxxxxxxxx <mailto:roc-chat-bounce@xxxxxxxxxxxxx> <roc-chat-bounce@xxxxxxxxxxxxx <mailto:roc-chat-bounce@xxxxxxxxxxxxx>> on behalf of dmarc-noreply@xxxxxxxxxxxxx <mailto:dmarc-noreply@xxxxxxxxxxxxx> <dmarc-noreply@xxxxxxxxxxxxx <mailto:dmarc-noreply@xxxxxxxxxxxxx>>
*Sent:* Friday, April 24, 2020 12:28 PM
*To:* roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx> <roc-chat@xxxxxxxxxxxxx <mailto:roc-chat@xxxxxxxxxxxxx>>
*Subject:* [roc-chat] Re: Vacuum Pump
I found a cheap pump at Harbor Freight. They have two grades, the cheap one was about $100 when I bought it about 4 years ago. Used it for checking altimeter along with a bell jar I got from Amazon.
Sent from my iPhone
On Apr 23, 2020, at 9:51 AM, John Coker <john@xxxxxxxx <mailto:john@xxxxxxxx>> wrote:
I have used a venturi as well for vacuum bagging. (I use a system meant for laminating: https://www.qualityvak.com/air.html.)
I'm sure a true vacuum pump would get a harder vacuum, but for most purposes a venturi works well enough.
Now, if you don't have a good air compressor, then a venturi is less appealing.
John
On Thu, Apr 23, 2020 at 9:14 AM James Dougherty <jafrado@xxxxxxxxx <mailto:jafrado@xxxxxxxxx>> wrote:
Lee
https://youtu.be/cDIooANLU3Q
that Nike Nike I flew off your tower had the sustainer bagged
with this pump:
https://www.fibreglast.com/product/1148_Vacuum_Generator/Vacuum_Bagging_Pumps
fins bagged with food-saver
https://www.amazon.com/dp/B07VPRW77Z/ref=cm_sw_r_cp_api_i_C6BOEb8Q8FW1V
best bang for the buck...
thanks Dierking for your remora cam
On Apr 23, 2020, at 8:27 AM, Lee Scott (Redacted sender
"leescott91006" for DMARC) <dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx>> wrote:
Guys in the know
I am going to be purchasing a vacuum pump in the near future
and there seems to be quite a few options.
I plan to use it for the following:
- degassing propellant for research motors
- vacuum bagging of composite laminates for fins and tubes
- testing of electronics in a chamber.
I am not necessarily looking for the best price. I am looking
for a pump that will meet my needs and not be something I need
to worry about not performing as expected.
Does anyone have any recommendations?
Thanks
Lee
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