I just emptied the cavity of the BP.
Sent from my iPhone
On Sep 5, 2017, at 6:12 PM, Dave Barr <dhbarr@xxxxxxxxx> wrote:
To clarify: did you keep the delay grain or was that epoxified as well?
On Tuesday, September 5, 2017, Dave M <dmarc-noreply@xxxxxxxxxxxxx> wrote:
54mm. I believe they were a J295 and a K570.
Good point Kurt. Maybe I was just unlucky with those two launches. At first
I thought I was cutting off the oxygen supply somehow at the base of the
motor (I helped a guy who was down to his last igniter when I noticed he
had heavily taped up the bottom of the motor) but I just had the red cap on
and even cut an X cut into it after igniters failed. It was only later that
I realized it was the motors I filled with epoxy so I got suspicious. Now
I'm paranoid to do that again. On some small Aerotch motors I've just used
Vaseline instead of BP with some tape over it, but figured epoxy is a
better alternative?
Sent from my iPhone
On Sep 5, 2017, at 4:54 PM, Kurtgug@xxxxxxxxx <kurtgug@xxxxxxxxx> wrote:
Once you burn the first igniter without lighting the motor, it is always
harder to light it with the second, and even harder with the third. The
core gets coated with soot which acts as an insulator. If you had the
pyrodex pellet in there, it is hard to imagine that not lighting. Maybe it
did light but fail to light the fuel. That would really coat the inside
with soot.
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On Sep 5, 2017, at 4:44 PM, Dave M (Redacted sender "muldavea" for DMARC)
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
No I was very careful next not to disturb anything. And the epoxy dries so
quickly that I didn't think it would have any chance to soak thru anywhere.
Sent from my iPhone
On Sep 5, 2017, at 4:36 PM, Gregory Lyzenga <lyzenga@xxxxxxxxx> wrote:
On Sep 5, 2017, at 4:22 PM, Dave M (Redacted sender "muldavea" for DMARC)
<dmarc-noreply@xxxxxxxxxxxxx> wrote:
A while back, I had two Cesaroni motors that were not plugged but I didnt
want the motor to blow the BP charge. So I removed the BP and filled up
with epoxy. Problem was, in each case, it took maybe three attempts to
launch. Kept burning out igniters. Any thoughts?
In the process of removing the ejection charge, did you disturb or damage
the igniter pellet at the top of the grain? Since Cesaroni igniters are
basically just e-matches without a bunch of pyrogen, there is a pyrodex
pellet at the top of the motor to get the ignition going. If the epoxy ran
onto that, it might explain your problem. But on second thought that seems
unlikely, since there would be a delay grain between it and the ejection
charge well. Hmmm… I’m not sure...
- Greg
----------------------------------------------------------
Gregory A. Lyzenga <lyzenga@xxxxxxx>
Dept. of Physics, Harvey Mudd College (909) 621-8378
Claremont, CA 91711-5990 mobile (626) 808-5314
