On much much smaller motors, we use to purposefully debond the grain from
the casting tube. We would then epoxy the actual inhibitor to the grain.
Worked well, was just an extra step. We used a poster board wrap, which is
likely easier than a sliding into a fully formed tube.
I have also tried coating the casting tube with epoxy. Believe I used 30
min. With the heat of the slurry, the epoxy started to set up and made more
of a mess than anything. Grains were trash.
Dave
On Mon, Dec 19, 2022 at 10:09 AM Richard Nakka <richard.rocketry@xxxxxxxxx>
wrote:
What you might want to do is to calculate the Kn of the motor assuming the
bond has failed and burning occurs on the outside of the grain as well. If
the resulting chamber pressure is within the allowable of the motor (with
suitable safety factor) then a repair may be an acceptable option.
I've taken this approach in the past.
Richard
On Mon, Dec 19, 2022 at 9:58 AM Brinker, Mike <mikebrinker@xxxxxxx> wrote:
On smaller motors we use compression during curing, since sugar
constricts as it cools. The night temperatures dipped down below freezing
during this curing, so the grain shrunk and pulled away from the casting
tube.
On AP motors we slurry the casting tubes in R45 and curative to support
better bonding. Has anyone tried using epoxy or Karo syrup or ? on the
casting tubes while casting sugar?
The “naked grain” in the photo actually slides nicely into a new tube, so
we had a lot of debate on the best way to rebound it to the new tube and
save it — like coating it in RTV, thick epoxy, liquid nails, etc. Rick can
weigh in on what they ultimately decide to do...
On Dec 19, 2022, at 6:17 AM, William Schmiedlin <wschmiedlin@xxxxxxxxx>
wrote:
What if you coated the casting tube with some Karo syrup? Let that sit
for a day to evaporate the balance of the water out and it may give you a
better bond to the liner when you cast in the KNSB?
William
On Sun, Dec 18, 2022 at 7:52 PM Mike Brinker <mikebrinker@xxxxxxx> wrote:
Here is the 130 lb naked grain.
<image0.jpeg>
On Dec 18, 2022, at 2:50 PM, Rick Maschek <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Test firing was scrubbed, grain #5, the bulkhead grain with the smallest
core and the last one to be cast showed some casting tube debonding. Eric
slit the casting tube and we peeled it off. The Good news is that the
entire grain looked good, no cracks and only a couple of tiny voids (like
small bubbles). Surprisingly, considering it has the smallest core, this
was the hardest mandrel to remove with Eric having to pound on the aluminum
motor tube to remove it. The grain was very solid.
We are discussing how to repair it or if we make a new one.
On Sunday, December 18, 2022 at 10:43:55 AM PST, Daniel Kirk <
dk54321@xxxxxxxxx> wrote:
Can't wait to see the video!
On Sun, Dec 18, 2022 at 12:27 AM <dustin@xxxxxxxxxxxxxxx> wrote:
Your aren't going to static test it in that truck bed are you ?
Just kidding, I couldn't resist.
All the best,
Dustin
On 2022-12-16 09:23, Rick Maschek wrote:
Tomorrow may be the make-or-break day for Sugar Shot.
We will static test our 12" (300mm) five grain S-26,500 KNSB motor
with a total impulse of 355,000 Nsec
Finished 9' (2.7m) long motor case being transported to FAR
Rick
--
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