William,
With the KN not melting, and the SB easily melting to a clear liquid, you could
see the grains of KN collect on the bottom of the tube.
We tried that many years ago and unless the KNO3 and SB are stirred, the KNO3
settles out of the mix. I sometimes wonder if this also happens when people
overheat their KNSB mixture, pour into a casting tube, and then get some
settling before the mix cools sufficiently to prevent separation. This might be
most prevalent with larger grains that take some time to 'harden'. I've noticed
this on our 8 to 12" grains when we mix 135 pounds of propellant.
Another experiment would be to press the powder (much like BP rocket motors).
Not sure how much pressure you would need, or if you could make it stick
together well enough to survive a firing.
Many have tried this with very limited success...usually CATO when the pressed
powder collapses not to mention a much lower Isp. I have thought about
including some small amount of liquid (corn syrup? water?) to get it to as you
say 'make it stick' but haven't had time to try/test. Probably because I
already am happy with simply mix-melt-pour my KNSB propellant. The only reason
I would try the make it stick with pressure and a liquid would be to eliminate
the use of heating.
Rick
On Tuesday, February 20, 2024 at 08:04:15 AM PST, Bruce Beck
<bbeck7@xxxxxxxxx> wrote:
William: Pressing sugar/KNO3 fuel works just fine using black powder
techniques.The finer the particle size the faster the burn rate.The press
pressure is limited by the strength of the casing tube material.
On Tue, Feb 20, 2024 at 8:02 AM Lincoln Ross <lr21643@xxxxxxxxx> wrote:
Rotisserie
On Tue, Feb 20, 2024, 1:59 AM Oliver <hauver.1@xxxxxxxxx> wrote:
I’m very interested in this. Is there a gelling agent that could be used to
keep the Kn in suspension but that could withstand the melting temps of SB?
Something that could also be fuel during combustion? Maybe methylcellulose?
Oliver H.
On Mon, Feb 19, 2024 at 9:31 PM William Schmiedlin <wschmiedlin@xxxxxxxxx>
wrote:
I did this in a test tube a few weeks ago. I heated the tube using a hot air
gun.
With the KN not melting, and the SB easily melting to a clear liquid, you could
see the grains of KN collect on the bottom of the tube.
I'm thinking that you are not trying to get the SB to fully melt, just become
sticky enough to start bonding with the KN and let out some of the air?
Another experiment would be to press the powder (much like BP rocket motors).
Not sure how much pressure you would need, or if you could make it stick
together well enough to survive a firing.
Regards,William
On Mon, Feb 19, 2024 at 2:23 PM Steve Peterson <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
Great work! Any idea what the density of the resulting grain is? Also, have
you attempted to ascertain how well bonded the propellant is to the inhibitor?
--Steve
On 2/19/24 11:50 AM, Patrick Naumnn wrote:
First attempt was overwhelmingly successful but I should have 2x grains good
enough to test fire. I set the oven to 225F for an hour and took temp
measurements of inside the coring rod and the air temp. The oven air temp was
130C+-5C and the core reached 110C in a little under an hour and I shut down
the oven and let it cool down slowly inside the oven. Unfortunately the temp
data did not save so I don’t have anything to show. These were also using
uncalibrated thermistors so there is quite a bit of uncertainty and potential
inaccuracy.
One thing I didn’t think about prior to casting is that the powdered mixture
is about half the density of the liquid/cast mixture. This means that the
casting tube needs to be twice as long if you start with a powdered mix.
Another thing I’m going to have to change is the casting cup. On the first
attempt it was 3d printed out of polycarbonate. I was hoping the mixture would
be thick enough to not find the tiny holes in the 3d print but it did. I may
try adjusting setting to achieve more water tightness. I’m definitely going to
have an aluminum version made up for the next attempt.
I’ll write up more about this after the next attempt. I also need to take
more pics.
On Feb 19, 2024, at 4:36 AM, Ben Brockert <wikkit@xxxxxxxxx> wrote:
I don’t think it’s particularly more dangerous than any other method, in an
electric oven with a reasonable temperature setting, and from a personal safety
perspective it is clearly much safer to disconnect an extension cord than to be
hand stirring mixed semi-molten propellant.
We have discussed it before, I have not yet tried it. If you decide to take a
scientific approach to it, an interesting test would be to do an excessively
long bake of a couple coreless grains, like ten hours, then light one from the
top and the other from the bottom to see if there is any stratification that
affects the burn. Work down by half times if there is.
The biggest challenge is that indirect heating will be very slow to heat a
thick grain through. A toaster oven with a forced convection setting (an
internal fan) would both increase heat flux and reduce temperature variations.
On Sunday, January 21, 2024, Patrick Naumann <naumap23@xxxxxxxxx> wrote:
Hey all,
Recently I had a thought that I can't find any information about on the
internet so I figured I would ask here before diving deeper and testing the
idea myself. Has anyone ever sintered/cast sugar grains in an oven? What
reasons are there to not do this? Will the difference in density cause the
potassium nitrate to sink to the bottom or is the mixture too viscous?
So right now I am working on getting some jigs/caps made so I can try to cast
KNSB grains in a small toaster oven (placed outdoors with plenty of clearance
from buildings). I know that this may be extra dangerous so more precaution
than usual will be taken to ensure safety. I'm thinking of mixing the powders
very thoroughly, then pouring in the casting tubes with coring rods in place,
packing down and then running the grains through some kind of temperature
profile. I think the key with this test will be to get the right temp profile
and walk the line of melting point. I may also try to add a top cap with a
compression spring and add some pressure. All materials used can handle the
~120C I'm planning on trying this with. The coring rods I plan on using are
hollow and there will be some kind of temp sensor in there.
Thanks, Patrick Naumann
