[SS-Propellant] casting vibrator

[dormans]

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From: ss-propellant-bounces at exrocketry.net
[mailto:ss-propellant-bounces at exrocketry.net] On Behalf Of Rich Nakka
Sent: Sunday, November 27, 2005 1:08 PM
To: Mateica Vlad
Cc: ss-propellant at exrocketry.net
Subject: Re: [SS-Propellant] casting vibrator

 

Mateica Vlad wrote:





Rich Nakka  <mailto:richnakka at rogers.com> <richnakka at rogers.com> wrote:

Gents,
While in the process of organizing a stack of technical notes &
correspondences, I came across something of interest. In correspondence with
a fellow rocketeer in Denmark some years ago, he told me about a vibrator
that he used to aid casting of propellants, which was apparently very
effective in helping the slurry to flow and fill all spaces in the mould.
3.0 kW motor
Eccentric flywheel to produce a 25 Hz vibration
Vibration amplitude 2.3 mm.

Something to consider for our casting of those large 34 kg segments. This
may help in maximizing our propellant density?

Richard
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Interesting ideea Richard. For some good results we need to calculate the
excentric dimensions(diameter, mass) and to make a controlled temperature
curing oven. In this way we can cast the propellant segment, put it into the
oven(where is the vibrator) and slowly cool the oven so that the density
well be maximized. we can't cast the propellant into the vibrating mold. the
oven can be made simple with a termostat and a heating coil. the electronic
schematic for the termostat cand be provided by Prodan Paul from the safty
team(he is making a termostat right now for me to easy my casting procedure)


Vlad

 





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Good ideas, Vlad.
Some things we need to bear in mind. 
We may well be casting the segments "in the middle of nowhere". How much
wattage is available, etc. (a decent gasoline generator should be able to
provide the power we need?)
For a single firing, 12 segments need to be produced. So the time a segment
can spend in the "curing box" would be limited. Perhaps have several curing
boxes?

Richard

 

I suspect that the larger the grains get, the easier it will be to get close
to theoretical density.  I've notice that everything else being equal, the
larger a grain is the better its density.  The nice thing about Sorbitol is
that you can heat it well beyond its melting point, with no carmelization,
before pouring it.   This has been necessary while casting at the RRS's test
area on cold, windy days.  The amount of heat that the propellant loses in
the transfer from the pot to the mould, when it's a thin ribbon, can be
significant.    By overheating it you can ensure that when it gets in the
mould it is still hot enough to be fluid.   We may be able to do that to an
extent if we use a sugar alloy since the addition of sucrose doesn't seem to
raise the overall melting point of the alloyed sugar.  I think that with
careful pouring and preheating tools and moulds we should get the necessary
density on a segment that weights 34 kg.  If we have access to a vibrating
table, or similar, that we could place that mould on while casting, that'd
be great.  Definitely couldn't hurt. 

Randy

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