I’ve heard about the 12 volt requirement for First Fire’s too. But, I’ve
successfully used them several times on 2nd stages using a 9 volt battery power
source and PET 2 timer. I suggest you ground test whatever you want to try
first. The Raven has a test program that works nicely.
And sorry, I don’t understand why you can’t use a CTI motor for your project?
I believe the mid-power CTI’s are easier to light with the supplied igniter.
Pieces of a pyrodex pellet work great although they are fragile. But, a little
epoxy to adhere the piece of pellet to the igniter and you’re set. The pellets
are available through places like Cabela’s.
Just like the chat conversation we had about using BP for ejection charges,
just because the cost of a larger quantity of something looks more attractive,
you have to consider what you are going to actually use and how you are going
to safely store it.
BTW, Aerotech had a table at LDRS and I asked about their development of the
head-end (forward) ignition system for their commercial motors and they said
they will be doing additional work on finishing the design this year.
On past projects, I had a couple test points on the outside of the airframe to
check the resistance of the air start igniter at the pad. You can compare to
the info obtained before installing the igniter as a reference. This provides
some reassurance that the igniter is OK.
Richard
On May 23, 2018, at 10:41 PM, Rick D. <rocketrick@xxxxxxxxx> wrote:
Terry,
An altimeter is unlikely to be able to directly fire anything requiring more
current than an ematch (the Quest Q2G2 counts as an ematch). So, the issue
becomes, "How do I get an ematch to light an APCP motor?"
Depending on how much room you have in the core and nozzle throat, you've got
a few options:
1) Copper thermite. It's easy to ignite, and throws molten copper at the
motor core, lighting it easily. Drawback is that you need a big enough throat
and core to accommodate a "package" containing the powder. Great for K and
up, but hard to use on anything much smaller.
2) Magnalite, Igniterman, or similar pyrogen "dips". These can be good, but
tend to dry out on the bottle, requiring constant thinning with acetone or
MEK. May be hard to come by nowadays.
3) Pyrodex pellet or black powder motor piece wedged or glued into the top
grain core. If it will fit, a Pyrodex pellet or the unwrapped black powder
grain from an Estes mini motor can be pushed into the top end of the upper
grain core. If it's too big, break one gently with a hammer, and use a small
chunk the same way. Place the ematch against the Pyrodex or black powder
chunk, and it will light it easily.
Hope this helps!
Rick Dickinson
On Wed, May 23, 2018, 10:16 PM Terry McKiernan <terry@xxxxxxxxxxxxx
<mailto:terry@xxxxxxxxxxxxx>> wrote:
Hello all,
Still trying to get my 2-stage high-power rocket project ready for the
June launch. I have a question about igniters I hope you can all help
me with. Basically I am looking for a recommendation: should I use the
igniter that comes with the motor, or buy an igniter more suitable for
airstarts, if there is such a thing?
My design uses two 3" rockets which are outfitted with Aerotech motor
retainers, and I have Aerotech casings, so I've only used Aerotech
motors with them. These are 38mm motor mounts and I'll be using class H
or I motors for the sustainer stage.
I am concerned that the Aerotech motors will be hard to start with a
small battery that can fit in a payload bay. I found a few posting
online indicating that Aerotech's igniters require 12V and can pull 15A+
momentarily when they short & burn. This is OK I guess for a ground
control system with a big fat car battery or marine battery attached.
But, it seems like an awful lot for an altimeter battery.
The airstart will be controlled an a Raven altimeter, and it does
support having a small 1S LiPo for the altimeter and a second battery up
to 20V for the pyro channel. And, yes, I can get a 2S 30C 12V LiPo on
Amazon. So, theoretically it should be able to start the motor using
the Aerotech igniter.
Alternatively I could buy some other igniter, or ematch, or make my
own. Any recommendations?
I am tempted by this ClusterFire kit, which promises 1 second burn at
5400F, using 6V and 2.3A:
https://www.rocketflite.com/store/index.php?route=product/category&path=61 ;
<https://www.rocketflite.com/store/index.php?route=product/category&path=61>
Or maybe H-3 Compound?
https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/H3-Igniter-Dip ;
<https://www.apogeerockets.com/Rocket-Motors/Motor-Starters/H3-Igniter-Dip>
Or MJG?
https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator ;
<https://electricmatch.com/pyrotechnics/see/6/5/mjg-firewire-initiator>
Note that at the March launch my Aerotech igniter on one launch failed,
and I tried an MJG ematch I had bought from buyrocketmotors.com
<http://buyrocketmotors.com/> as a
replacement and it failed, and then I bought a FirstFire and it worked.
But, that was a ground launch not an airstart. In any case my only
experience with MJG was not good.
Or Slim Gem?
https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Slim_Gem_Starters ;
<https://www.apogeerockets.com/Rocket_Motors/Motor_Starters/Slim_Gem_Starters>
One thing i note about Slim Gem is they also require 12V just like
Aerotech. Also according to the Apogee site they burn at 1400F, vs. the
5400F claimed for ClusterFire. Quite a difference...
Or Quest Q2G2?
http://www.buyrocketmotors.com/quest-q2g2-3-initiators-6-pack/ ;
<http://www.buyrocketmotors.com/quest-q2g2-3-initiators-6-pack/>
Or ... probably lots of other choices out there?
Thanks for any suggestions!
Terry McKiernan
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