I believe the professional vacuum method involves sucking the propellant
thru a funnel and slit plate under vacuum.As the propellant ribbon emmerges
from the slit plate into the vacuum disolved gas bubbles out and by the
time it hits the main grain it has been degassed.The drop distance between
the slit plate and the main grain must be optimized for complete
degassing.The wider the slits the longer the drop distance has to be to
optimize the degassing.
On Tue, Sep 10, 2019, 4:03 PM <mark.spiegl@xxxxxxxxx> wrote:
I am wayy behind on my email so this msg is a delayed response:
On Behalf Of Troy Prideaux wrote:
1stIf I vaguely recall (I could be mistaken) it was Mark Spiegl (?) who
hementioned this process here about maybe 15 odd years ago. If I recall
For me, centrifugal casting worked extremely well. I was able to get
consistency and measured densities much better than I ever achieved with
vacuum processing. I suspect Anthony Cesaroni is 100% correct that tossing
propellant in a bucket and pulling a vacuum doesn't do much. It needs to be
processed under vacuum.
If I were going to make a Bates grain, even 6" or 8", I would probably use
centrifugal casting. You can buy a wood lathe for a few hundred dollars,
and the centrifuge parts are trivial to make.
When the centrifuge stage is done, a clear line of demarcation exists
between liquids and solids. Just bore-out the useless gummy core. My
measured density was very close to theoretical.
On Behalf Of Doug Jones wrote:
smallPerhaps you could put the mix in a funnel and extrude it through a
nozzle into the motor case in a vacuum chamber? With a rubber ball
floating on the surface to block the funnel as it goes empty.
The funnel method did not work for me. I think you need a pourable
propellant. My stuff would "glop" in the funnel and then "glop" in chunks
into the lower chamber. Measured density was poor. Again.. I think exposure
time to the vacuum isn't long enough to do anything.
--MCS--