[BProckets] BP tubeless motors (tubelesses)- preparations

[flint hapirat]

Hi all, 

After a long period of "other things" I'm getting back
to tubeless motors. This is a preliminary update,
listing the tools and process. 

If you are don't know what I mean when I say
"tubeless" (after all my last post on the subject must
be 2 years ago) - it's a small grain of BP, with an
internal core, burning and flying on it's own. No
tube/casing, no nozzle and no plug. The fly just fine
without these


I have completed a full metal ramming system (not lath
work, good old improvised stuff, steal epoxy and so on
- lath work is too expensive for me). btw - it's my
first all metal tool... (my tools are wood based, hand
drilled/made). The system is made of an al. tube 10mm
ID and a ramming rod 10mm OD with a centered hole
(broke 2 drill bits on that one) that holds a core rod
in place. I can change the core rod length at will, of
course. It's an upgraded star pump.

A high quality BP (willow charcoal, 75, 15,10, ball
milled for 3.5hr, dry time: 2hr) is used for these
motors. The BP is used in powder form, added with
binders (grinding both in a mortar and pestle until
the mix is totally homogeneous, and then some) added 
doubly distilled water, mixed thoroughly and than
rammed (one batch per motor, no successive ramming). 

Initial tests I've done in the past showed that just
adding water (5%) is better than any other combination
of 5% 1:1 water and ethanol or just 5% ethanol, and
even better than 5% added dextrin. 

For the tests I have chosen the 10mm OD motor system
allowing me to use small volumes of the same BP batch
(my batches are 200gr each) for consistency. Also this
is a simpler system to handle. Up-scaling is planned
and will be also reported in the future.

10gr of BP are added with the additive before
grinding, wetting and ramming. Each motor weighs ~3gr
after drying (in the sun, 1hr). The grains come out of
the tool smooth and nice, no cracks of any kind. They
almost look like they were made of black shiny rubber.
They are very rigid and strong.  
Motor specs:
10mm OD
~2.5cm long
2cm long core, 2mm ID

Basically the stronger the grain/motor the longer (in
millisecond or so) it will hold up to the pressure of
the burning/expanding grain inside. Hence, a good
binder can be of use. To this end I'm testing a list
of binders/adhesives that may be of use and are
commonly available. If anyone as a good suggestion,
and IF I can find the reagent here I will be happy to
add it to the list.

So far I have made a set of 3 motors per test/binder
with the following:
1. 5% water only
2. 5% dextrine + 5% water
3. 5% potato starch (same stock which was used to make
the dextrine) + 10% water (got *stuck* with 5% water)
4. 5% corn starch + 10% water

Future tests will include other adhesives/binders.

For stabilization I glue the motors with hot melt to a
simple, thin (no. 8) spaghetti rod (watch out for
these - the easily break and snip; watch out for the
wife too – she will explode, if she gets you messing
with her spaghetti). 
A simple, thin black match is folded and inserted to
the bottom of the tubeless. No need for priming the
core. Storage in a cold dry place does not effect them
if they are dry.

Now the disappointment - still didn't launch these but
I hope to do this soon. 
Reports will follow...
Cheers all, 
Flint 


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com