[NRV Rocketry] Questions about outfitting an avionics bay with power-safety flags

[Bob Schoner]

Tweeks,

I really like your ejection charge holder idea and am very interested to see
how that works.  I had to attempt level 2 3 times because, in part, I had
issues orienting the ejection charges (Robbies flashbulbs in cardboard
tubes) so they didn't blow a hole in my cardboard airframe.  You have an
elegant solution for making sure it fires up.  Eventually I found out that
tubes weren't required, a corner of a baggie works just fine and is less
directionally focused.

As far as altimeter arming, I think I've tried just about everything there
is - and I've never had a problem.  I started with 1/4" phono plugs making
sure the contacts were oriented so they were perpendicular to expected G
forces.

I've also used the twist wire method without any problems.  I wrapped the
exposed wire with masking tape and pushed it into one of the barometric
ports.  Later I would just use masking tape and taped the ends to the body
just below the port.

Now I prefer the Aerocon rotary voltage select switch in my 3" airframes.
For 4" and larger I use a remove before flight pull pin/flag to safe and arm
the electronics.  Unfortunately I have all of them mounted so I can't take
pictures.  I have some Visio drawings that I'll find and send to you.  The
basic idea is to use a brass tube with cut outs for micro roller switches
wired to NC side.  I stagger the switches so I can pull the pin about 1" and
arm one altimeter first, listen for the beeps and then arm the second.

I like the visual reminder of the RBF flags and  the geekiness of it.  The
rotary selector switch are probably the simplest and dependable.  I haven't
tried the screw switches, but they are probably another good choice.
Hope we can see it fly soon!

Bob
On Wed, Jul 6, 2011 at 12:33 AM, Thomas Weeks <tweeksjunk2 at theweeks.org>wrote:

> **
>
> This is a question for you high power guys who have been shooting H and up
> birds for years.
>
> Background:
>
> -------------
>
> So my first HP rocket is about ready to fly... and I plan on using it to
> get my L1 (H) and L2 (J) certifications. The L1 is no problem. Up, pop,
> float down. But as most of you know.. L2 certification also requires a
> written test (no problem) as well as "Active recovery", or a way of
> measuring your altitude and ejecting multiple chutes at precisely the right
> times to safely recover my rocket.
>
> Well.. I've now mostly built my avionics bay, or "e-bay" and wired in a
> GWiz LCX flight computer:
>
> http://www.facebook.com/photo.php?pid=1049573&l=3b9cc7e689&id=1844028171
>
> http://www.facebook.com/photo.php?pid=1052820&l=fde4de7d63&id=1844028171
>
> http://www.facebook.com/photo.php?pid=1052821&l=8f9d1e56c2&id=1844028171
>
> http://www.facebook.com/photo.php?pid=1052825&l=878029acee&id=1844028171
>
> http://www.facebook.com/photo.php?pid=1052823&l=079bcf0bff&id=1844028171
>
> http://www.facebook.com/photo.php?pid=1052824&l=d39d643ca4&id=1844028171
>
> Here are some other pictures of other people's e-bay construction and
> products:
>
> http://www.vanderbilt.edu/USLI/2011/media.php?gallery=jan_19_2010
>
> http://www.apogeerockets.com/electronics_bays.asp
>
> http://www.rocketryplanet.com/content/view/2960/95/#axzz1RIL7aYxk
>
>  My Question:
>
> -------------
>
> Anyway.. my question for Bob and other experienced Rocketeers..
>
> What should I use for my flight computer's power safety switch?
>
> So you're supposed to have a power arming safety circuit to ensure that
> your ejections charges don't blow before you launch the thing... They
> usually look something like this:
>
> http://aeroconsystems.com/cart/products/RBF4-47-10.html
>
> And are hung off something like a 1/8th " audio jack (where the normally
> closed circuit is open when the audio plug is in... and removing it
> completes (or closes) the circuit.. and powers up the computer). However.. I
> hear that the flight vibration can really make those switch contacts bounce
> around, which can reset the flight computer.. which leads to big expensive
> crashes. So a lot of folks use these high-G rated switches like this:
>
> http://aeroconsystems.com/cart/products/PCB_Screw_Switch-110-0.html
>
> or
>
> http://www.aeroconsystems.com/electronics/switches.htm
>
> Not nearly as cool/sexy as the "yank it out" audio plug that I want to use.
> :)
>
>  So what do you other HP folks recommend? Slide switches? Hard wired
> toggles? Audio jack/plugs?
>
> Tweeks
>
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>
>
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