Model Forum / General / Rockets / March 2006

I've decided to fill in the time between now (mud season) and summer (rainy
season) with a small research project. I figured I'd ask folks to point out
any obvious flaws in concept or methodology before I spend a lot of time on
it.

Scanning the net for information about deployment charges, I find lots of
anecdotal reports of the effectiveness of various powders and charge prep
methods, but no specific comparative data. Given that I live in a place
where setting off a couple hundred small charges will never be noticed, I
thought I'd try to develop such data. If it's already out there, PLEASE
point it out before I get started :)

GOAL:

Determination of viable alternatives to commercial Black Powder, and
generation of a table of relative effectiveness for different powder types
and canister configurations.

APPARATUS:

A piece of electric fence wire (continuous steel wire, approx 1/16" in
diameter) will be stretched horizontally between two anchor points, and
tensioned to a specific loading before each test series. The actual tension
is somewhat arbitrary... at least 150lbs, max something less than the
breaking tension of the wire. The idea is to create a replicable condition,
with no primary resonance.

Below this wire, at one end, is secured a BP "cannon", simulating a 4"
rocket body tube. A 16" long, ~16 ounce "slug" representing a nose cone will
be suspended from the wire by 1/4-20 eyebolts at two points, in a manner
which allows the slug to hang level on the wire, and to be inserted in the
cannon without putting tension on the wire/eyebolt connection. After firing,
the slug will be suspended from the eye bolts no more than one inch below
its starting position.

Before each test series, the wire will be tensioned and cleaned with a light
petroleum solvent (WD-40). Temperature and barometric pressure will be
recorded for later data adjustments. Further, a "reference charge" will be
fired to insure that the apparatus delivers generally consistent results.
This reference charge will be something like 1g of ffffG Swiss black powder,
in a specific type of charge container, wadded a specific way.

All charges will be ignited by the same type of low-current ematch,
specifically, built from Aerocon Hotheads coated with Shimizu H3, and fired
from a  12v high capacity battery. All pieces of the apparatus will be
created from standard materials so that they might be easily replaced in the
event of failure or excessive wear.

METHODOLOGY:

Each prepared charge will be inserted in the 'cannon', the 'slug' inserted,
and the charge fired. The distance the slug travels down the suspended wire
will be recorded. After each firing the 'cannon' and 'slug' will be cleaned
of any residual powder or debris. At least two firings of each configuration
will be conducted.

Charges will be prepared per the research matrix. A standard weight of
powder will be established and used for each test (probably on the order of
1g).  A commercial powder scale will be used to insure accuracy. Several
types of canisters and wadding methods will be tested, as well as several
different types of powder. Lists below (feel free to suggest additions)

Powders:
    ffffG Black powder (swiss, goex, red dot)
    fffG Black Powder (goex, red dot)
    Nakka's Crimson Powder
    Pyrodex P
    Homemade meal BP
    Homemade granulated BP
    Homemade sulfurless powder
    Composites (i.e. pyrodex + x% meal BP)

Containers:
    Plastic 2.0ml with snap cap (tall and narrow)
    Cardboard tube (shorter and more broad)
    Baggies
    Open pan

Wadding:
    This is the "meat" of the matter, and an area where I may be offering new
    info, if preliminary tests pan out. Suffice it to say this will include an
    array of materials and methods, from loose "flash in the pan" discharge to
    tightly contained by a number of methods, depending on the charge
    container.

Hmmm... I think that describes it in general terms. I'm no technician, just
a backyard hack, so it wouldn't surprise me a bit to find that I've missed
something important. Comments and criticisms would be most welcome.

Kevin OClassen
NAR 13578
TRA 10569

kevinREMOVEMEatREMOVEMEback2bed.com