That's sweet. Thanks Mike for sharing ...
On Sat, Apr 25, 2020 at 10:48 AM mnkramer.net <kramer@xxxxxxxxxxxx> wrote:
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> 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 <roc-chat-bounce@xxxxxxxxxxxxx> on
behalf of dmarc-noreply@xxxxxxxxxxxxx <dmarc-noreply@xxxxxxxxxxxxx>
*Sent:* Friday, April 24, 2020 12:28 PM
*To:* roc-chat@xxxxxxxxxxxxx <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> 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> 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> 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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