I got one more idea for you. If the body is aluminum and the swing valve
is coated steel you can hold it open so it can flow both ways with a
neodymium magnet. and when the disconnect is done the magnet gets pulled
off by the falling away side because it's attached by a tiny cable to
that side.
Yeah, I'm just throwing stuff off the top of my head out there. lol
I could make that work though I'm sure of it.
Monroe
-------- Original Message --------
Subject: [AR] Re: Quick disconnects...
From: Ben Brockert <wikkit@xxxxxxxxx>
Date: Sun, December 09, 2018 9:35 pm
To: arocket@xxxxxxxxxxxxx
I've seen a lot of QDs with double shut off, but that's not checking.
Or rather it is checking, but only after it has been disconnected.
I've launched a couple aluminum double shutoff racing fuel QDs and
they worked for fill and drain. You can't disconnect before the rocket
launches, which makes the operation time critical for upper stages.
You might want dry break on at least one side if you have a hypergolic
combination and the QDs are anywhere nearby. They tend to be heavier
though. For your application if you are pressurizing through the
propellant fill lines then that might be sufficient to clear them out.
On Tue, Nov 13, 2018 at 8:33 AM Paul Breed <paul@xxxxxxxxxx> wrote:
I have a reliable QD that works for the pressurization line I used on blue
Ball...
It uses standard Air QD's Alas if you get one in stainless so its
chemically compatible for fill and drain of propellants,
then its really heavy.
Most of the QD designs described here have a common feature, a check valve.
I want to be able to do remote fill and drain like the big boys, so it has
to flow both directions....
and I don't want to add the weight of an actuated valve on the rocket side.
The sealing surfaces are not the problem, the Rocket side shutoff when
removed is the problem.
On Tue, Nov 13, 2018 at 7:38 AM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
For my peroxide rocket I just bought a swagelok QD. The male side went on
the vehicle; the female side had a 90 degree fitting behind it that went
to the high pressure He supply. There were four welding rods soldered to
the release ring on the female side that went to a disk that attached to
an air powered cylinder that was in turn secured against the 90 degree
fitting.
Hitting the pneumatic cyclinder w/ 100 psia pulled the bezel back,
residual pressure inside the QD popped the whole female side assembly off
the vehicle.
Dave Crisali design; I believe the female side assembly is still stored at
the MTA.
Bill
On Tue, Nov 13, 2018 at 8:12 AM Edward Wranosky <edwardcw@xxxxxxxxx> wrote:
An IREC team I worked with used a simple and reliable quick disconnect.
The rocket side was a drawn aluminum tube that was tapped for 1/2 NPT and
screwed into a check valve. Double grooves were put in the outside of
the tube using spiral rings to hold a 'flange' piece with two 3/8-16
tapped through holes.
The fill piece was essentially the same, except 1/4 NPT, with the fill
nipple having two o-rings on the outside. The flange on that piece was
not threaded. Two 3/8-16 nylon pyrobolts were used to secure the
assembly together with redundant e-matches in both bolts. It worked ~25
times with no failure.
Edward
On Tue, Nov 13, 2018 at 7:45 AM Evan Daniel <evanbd@xxxxxxxxx> wrote:
The last QD I fabbed was about the simplest possible and worked well.
Rocket side is a hole in the airframe. Behind that, a fitting with an
NPT joint on the inboard side to a check valve to the tank. Outboard
side of the fitting is a smooth bore with an internal o-ring groove,
with enough depth that there's plenty of margin on engagement
distance. External side is a short piece of hard tubing to a 90 degree
compression fitting to a flex hose. The joint is manually assembled,
then secured with a combination of cable tie and a piece of music
wire, wrapped around the entire circumference of the airframe and over
the elbow fitting. (That is, both halves of the fitting are secured to
the airframe, and there's nothing directly holding them to each
other.) The cable tie provides a convenient adjustment and tensioning
mechanism. A high-current source (12V lead-acid battery + relay or
similar) is then connected to the music wire via alligator clips. A
small piece of fiberglass or similar can be placed under the wire if
needed to insulate from or protect the airframe. On actuation, the
wire heats up and residual pressure in the line breaks it.
Disconnection force is provided by line pressure.
Cable ties are McMaster 7295K3 or similar. Use two to get two of the
mounting hole ends that the wire can securely attach to.
We only ever used it for nitrous on fairly conventional small amateur
hybrids. It's possible it wouldn't work nearly as well with an
incompressible liquid.
The only aerodynamic feature is a clean hole in the airframe slightly
larger than your fill tube OD.
It won't scale up very far before finding strong enough cable ties
becomes tricky, but if you can tolerate a small fill tube it should be
fine. If you're trying to fill at very low pressure I doubt it will
work, unless you can arrange to pressurize the line with an inert gas
or something after the fill is complete.
Evan Daniel
On Tue, Nov 13, 2018 at 5:05 AM Paul Breed <paul@xxxxxxxxxx> wrote:
Looking for ideas on light, high flow, and aerodynamically clean quick
disconnects...
I've been spending a lot of CAD time drawing QD concepts and its
deceptively hard.
I really want them to be reliable, I want to end the mad dash to the
pad where some one shakes the QD loose
form the rocket in a hazardous state... (Happens at least 50% of the
time at FAR)
I'd like the rocket side to be easy to fabricate, the ground side can
be more complex as long as its sturdy.