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.
Sent from my iPad
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
