Stephen:
Sure, no worries.
Bill
On Fri, Oct 9, 2020 at 8:53 AM Stephen Daniel <swd@xxxxxxxxx> wrote:
When you have completed the design for an actuated burst disk, I'd be very
interested in seeing it.
Thanks!
On Fri, Oct 9, 2020 at 10:47 AM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Troy:
I certainly get the attraction of a ball valve but after spending some
time with my favorite valve design manual and reviewing the history of how
I got to this solution (mainly, I already had the valves for a liquid
project) and reflecting further on Colin Chapman's mandate to "simplify and
add lightness", I am concluding that a actuated burst valve is the correct
solution.
This probably means designing one--although I will look over existing
industrial burst valves to see if modification is an option--but that
effort should get a solution that does not leak and that is given to firing
only when the computer says "go". In part, this decision keys off of the
two flight computers providing lots of high current pyro actuation lines
(I'm thinking about dual redundant initiators) but it also reflects my view
that this is the simplest solution as well as likely lowest mass.
Bill
On Thu, Oct 8, 2020 at 3:40 PM Troy Prideaux <troy@xxxxxxxxxxxxxxxxxxxxx>
wrote:
Bill,
¼” ball valve with a miniature geared motor directly driving the
shaft. You can cut down the supplied handle to use its stop tab to limit
the turn to 90 deg. I’ve used that solution before a few times. It’s a CHAD
solution but it works (even to 1000psi and beyond) and won’t provide a
significant mass penalty. Miniature geared motors come in various gear
ratios to provide solutions of significant torque. You can simply mount the
valve and geared motor to a piece of 3mm ply or MDF via zip ties and voila…
BTW: yes the Chinese cheap ¼” ball valves are good for the job.
Regards,
Troy
*From:* arocket-bounce@xxxxxxxxxxxxx [mailto:
arocket-bounce@xxxxxxxxxxxxx] *On Behalf Of *William Claybaugh
*Sent:* Friday, 9 October 2020 7:52 AM
*To:* arocket@xxxxxxxxxxxxx
*Subject:* [AR] Re: Vibration Tolerant Pneumatic Valve
Wyatt:
This is a normally closed valve so only spring force is keeping it
closed; given the strong “organ pipe” longitudinal vibration in
solids—which my vibe table is not duplicating (it’s intended for vibrating
mixed propellant under vacuum)—I’m suspicious that spring force is simply
not going to do the job.
A ball valve with a solenoid actuator (on a lever) seems a better bet
for staying closed but adds complexity and cost. I’ll have to chew on it;
perhaps a ball valve with pyro activation would be simpler?
Bill
On Thu, Oct 8, 2020 at 2:06 PM Wyatt Rehder <wyatt.rehder@xxxxxxxxx>
wrote:
A simple solution might be to use a NO solenoid, as you might be able to
spice up the actuator a bit and get the electric closure force stronger
than the spring return force. That might be enough to keep the leaks away.
In a similar vein, are you able to change the orientation of the solenoid
to the vibration? Or is the vibration axis pretty random.
Next option (which I haven't tried) they do make rotary solenoid
actuators. Which you could pair with a ball valve. That should be pretty
immune to vibration. But I can't attest to how reliable they are.
-Wyatt
On Thu, Oct 8, 2020 at 9:59 AM William Claybaugh <wclaybaugh2@xxxxxxxxx>
wrote:
Testing shows that the Lake Axial Solenoid valve in my pneumatic payload
separation system is leaking at 125 psia despite a 1000 psia rating (two
valves tested, both leaked); the leak is through the valve and caused the
latchup of the payload to the vehicle to fail within an average of four
minutes. Additional testing on my vibe table showed latch failure in less
than one minute in ten tests.
Can anyone suggest a solenoid valve good for at least 250 psia and
unlikely to leak under vibration?
Alternative suggestions to using a solenoid valve are welcome.
Thanks,
Bill