[BProckets] BP tubeless motors (tubelesses)- preparations

[Doug Sams]

Pics, pics, we need pics!

Seriously, can you post some pics and links?  That would be greatly appreciated.

Doug


flint hapirat wrote:
> 
> 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
> 
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-- 
doug dot sams at flash dot net