Hmmm, I'm not sure then. I've reused pvc but I put a layer of fiberglass on
the outside to increase strength. Your best bet would be to reduce the Kn
until it doesn't explode.
Trevor Mushung
On Jan 11, 2018 8:49 AM, "Sunny Gavali-Bhosale" <sunnygavali02@xxxxxxxxx>
wrote:
Fittings are same as you guys use there. I've given dimensions of PVC
pipe(using for motor) and got his green flag.
Twice I had used already used tubes because all were in OK conditions
because some times due to high pressure caps were puffed or if it
pressurize it leaded explode.
Sunny Gavali
On 11-Jan-2018 7:12 pm, "Tr Mu" <tl01001101@xxxxxxxxx> wrote:
It might be a lower quality pvc and it could contain microfractures. Are
you drilling into it at all? If so it might be that it's failing there due
to na weakened area.
Trevor Mushung
On Jan 11, 2018 8:38 AM, "Bill Kuker" <bkuker@xxxxxxxxxxxxx> wrote:
I think there may be some differences in pvc pipe around the world. I
remember one fellow who was from some western country, maybe the us, living
in Thailand perhaps, who was making pvc motors. The pipe and fittings he
used, and even the glue, were visually at least very different from what I
think of as pvc pipe.
Sunny - are you re-using the pvc pipe? I do not believe for a second any
pvc motor I have made would be re-usable. I use my steel nozzles many
times, but new pipe and fittings each time.
-Bill
On Thu, Jan 11, 2018 at 6:48 AM, James Yawn <jyawn@xxxxxxxx> wrote:
Sunny: Sounds like your propellant is good. Case is good, inhibitor is
good, case is firmly assembled...
I'm down to one suggestion: Reduce the Kn ratio on subsequent motors.
Try a half-length grain. If that CATOs, try a 1/4th length grain. Keep
reducing it until the motor works.
Then, knowing the Kn for a motor that holds together, you can design a
larger motor with the same max Kn by enlarging the nozzle throat and grain
core to match the small motor that works.
It's a crude method, but I believe it will work... eventually!
Jimmy
On 1/9/2018 9:36 AM, Sunny Gavali-Bhosale wrote:
Grains are truly hard like a rock.
I use method in which first I dissolve Kno3 and table sugar in water.
Then keep to boil and do a continue stir. When I feel it's almost nonstick
and ready to scoop I remove it from a skillet and start filling grains in
casings made for making grains actually a stand and already added
inhibitors in a casings.I use plunger to push propellant to avoid any
bubbles. After filling, let it dry for and then they are ready to insert in
a motor. At this time I've maintain the temperature so I do not maintain
temperature. At first I dissolve both at around 250'C and at last I keep it
on 150'C.
On 09-Jan-2018 7:48 pm, "James Yawn" <jyawn@xxxxxxxx> wrote:
Sunny: Sugar propellants produce a lot of ash, but when a motor burns
OK, almost all of it goes out the nozzle. That's the white smoke. A
little may remain in the motor, but it is in liquid form, and is not
thought to cause problems with large nozzles, such as yours. So that is
not my first guess as to the problem.
Did the grain burn after the motor burst? Sometimes they are
extinguished, sometimes they make a fireball.
Maybe I asked this, but don't recall... Is your propellant hard and
solid? It should feel like a rock. If it's crumbly, then you might have
disintegrating grains. Could you describe your process for making grains
again? Ingredients? Temperature? Technique? that might offer some clues.
Jimmy
On 1/9/2018 9:08 AM, Sunny Gavali-Bhosale wrote:
Sorry, I didn't get any grain particles. Just got casing with nozzle in
OK conditions about 70m to 80m away from test side.
I've read table sugar burst too hotter than other sugars. you may assume
sorbitol, dextrose. So this may be the reason that its producing too much
pressure inside than other motors produce.
My propellant lefts some ash after the burn.so, I guessed that might be
creating mess at nozzle throat to overpressurization.
On 09-Jan-2018 7:24 pm, "James Yawn" <jyawn@xxxxxxxx> wrote:
Sunny: I don't understand this question:
On 1/8/2018 11:47 PM, Sunny Gavali-Bhosale wrote:
Does propellant residue results in PVC motors?
Do you mean does the residue result in CATO?
The fact that your last motor had some of the cap left glued on means
that the glue is not the failure point.
Looking at your last test, and considering that you are using cardboard
inhibitor, (glued on with epoxy I presume,) my next guess is that the PVC
you are using is somehow weaker than anticipated.
I'd suggest making a motor with reduced pressure, either with a
half-length grain, or enlarging the nozzle throat and grain core to get one
that does not CATO, and build up from there.
Most of the PVC motors I've made used 1-1/4 inch tubing. You might even
try that, as it is well proven. It occurs to me that Richard Nakka has a
spreadsheet for calculating the strength of a motor casing. It's
"casing.xls" and includes PVC as one of the materials.
Did you find your propellant grain? They are often extinguished when a
motor bursts, and their state can offer clues as to what went on.
Hope to see one working soon!
Jimmy
