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Geeze this page is popular...
Copperhead ignitors (as provided with Aerotech motors) have a bad reputation
for being unreliable, which is probably why you are reading this tip in
the first place.
UPDATE:- I've been doing some more
research into the copperhead problem and I've discovered that once people
fully understand how the copperhead ignitor (and similar) work, then success
with these ignitors is greatly improved. Many people are claiming 100%
reliability which leads me to believe that lack of care by the rocketeer
is the main reason for having problems with these ignitors.
Understand that the copperhead and similar ignitors are made from 2 very
thin layers of copper, separated by an even thinner layer of insulation.
What this means is that these things are FRAGILE and prone to SHORTING
OUT. I have scoured the planet for tips and tricks and this is what I
have found:
- Run your fingers or a hobby knife down the edge of the ignitor to
remove any flashing (from when the copper was cut) that may cause a
short. Quite often you will see unwanted material being removed.
- Do not use clips with teeth - use the flat ones. The teeth can easily
short a copperhead type ignitor. If you have no choice, then put some
rubber or tape on one half of each clip.
- Try heating the end of the copperhead with a lighter and separating
the two layers of copper and attach a lead to each layer or use some
insulation tape and punch two holes in it and fold it over your copperhead
(like the quest ignitors). This greatly reduces the risk of a short.
- Do not use the cap that comes with your motor - tape the ignitor in
place as the cap can break the conductive or insulative layer and short
out the ignitor. If you do use the cap, make sure you put an ample vent
hole in it. (Most single use motors now come with a rubber band around
the nozzle and no cap). I like the red cap very much so I don't agree
100% with this tip - but do be careful when putting the cap on.
- Use a fully charged 12v supply for your launch controller (many people
try to launch on 7.2v)
- When igniting 'W' propellant, be sure to augment the igniter with
a slither of blue thunder propellant to be sure the motor gets up to
pressure quickly (or to light at all!).
Here's some more tips from the Rec.model.rockets newsgroup.
From: dcrcep@mizzou1.missouri.edu (Elmer M. Price)
Hi Folks: I have a comment on the reliability of Copperhead igniters.
Our small group has had no problems with these, once we figured out the
best way to use them. So, in spite of all the negative comments, we actually
really like these things. We have launched composites up to
and including I-sized motors with great reliability. For example, two
weeks ago, two of us (at the excellent St. Louis launch), launched two
I284
birds, one I161, one I211, two H123 and a few F's and G's. We had 100%
igniter success.
O.K. So what do we do to achieve such reliability? First, open the reload
pack and assemble the motor in the usual manner. Second, find
the Copperhead that came with the reload kit and THROW IT AWAY. What we
use are Copperheads which we purchase separately. These arrive from the
dealer (like Magnum) in a nice package and the igniters are not all beat
up and crimped and bent to heck like the ones which are provided in the
reload kit. We feel this is an important point. Second, since the H and
I (and larger) motors are a bit more difficult to light, we modify the
new Copperhead as follows (this idea came from RMR): take a slug of white
lightning propellant (we use the slug from a D9) and cut a very small
sliver (and I mean small, about 1/16 inch square and about 1/2 inch long).
Tape this sliver (Fred from our group optimized this point) to the Copperhead
by overlapping the bottom half of the pyrogen on the Copperhead with the
top half of the sliver. Use a small strip of
masking tape to attach the sliver to the copper below the pyrogen. The
point here is to ensure the tape is below the area where the pyrogen and
the sliver overlap. This is important because if the tape is higher up
the igniter, the sliver may fall off of the Copperhead and lead to a chuff
(ignition too far aft).
This modification is not necessary for G and smaller motors, since the
pyrogen is in close proximity (or touching) the propellant.
And this was added by: bday@fly.HiWAAY.net (Brian Day)
I've also gotten *MUCH* better reliability from Copperheads by not using
the red plastic cap over the nozzle, and just using a small piece of
masking tape to hold the igniter in place. This technique doesn't crimp
the Copperhead like the plastic cap does. Since doing this, I've gone
from roughly 50% reliability to darned near 100%.
Oh yeah, someone else on rmr recently suggested clipping off the pyrogen
part of an old, crummy Copperhead and using it to augment another
one, like you do with your sliver of propellant. Beats throwing it away...
Finally, regarding the red caps provided with Aerotech motors for holding
in the igniters,
From: Bob Kunz <bkunz@boi.hp.com>
You do know that one is supposed to provide a vent in the red cap? I would
presume this is to allow some leakage of pressure but enough to get the
white/blue/black propellant to ignite. Typically, I find that the red
cap is blown through when I recover the rocket. Only once was it blown
off at the launch pad. So far in about a dozen launches on RMS 24/80,
I've had no failures. But sure those are small grains compared to some
of the 54mm stuff.
From: curcio@telerama.lm.com (Larry Curcio)
Copper Head igniters have acquired reputations for unreliability. I'm
wondering if the problem is in the igniters or in the red nozzle caps,
which blow off during most Copper Head failures. IMHO, it's the sudden
release in pressure that makes ignition fail - by disrupting the newly
forming flame. When I use a piece of masking tape instead of a cap, I
don't seem to have the problem.
Editor's note (jjirvine@cyberg8t.com):
As of 11-96 Aerotech has made some efforts to eliminate the microshort
problem which is an artifact of the Coppercrap manufacturing process.
They have tried making versions with thicker insulator layers. While they
are more fragile and subject to peeling, they are more reliable than before.
Time will tell.
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