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Making a granulated r-candy powered aluminum rocket tube for 6" shells

Minamoto Kobayashi

Well-known member
Joined
Aug 25, 2010
Messages
480
Points
63
This new project allow to save and reuse aluminum body and sticks.
Please NEVER launch those kind of rockets near buildings and properties: the falling mass is noticeable and dangerous.
Open spaces like grass fields without trees is the best place to launch these beasts: You can rescue the undamaged debris stuck in the ground


The 300mm, 1.5mm thickness aluminum tube:
48135350292_f9428d7d00_b.jpg


My awesome custom tube support:
48135350062_3d09094d15_b.jpg


Tube inserted and firmly locked, threaded holes created for a special add-on:
48135349912_96eb11a614_b.jpg


I created an extra tool, a sort of add-on, that make an useful nice recess and avoid unwanted tube sliding:
48135349752_ca964c87a4_b.jpg


Add-on mounted:
48135254961_6ecf50d20d_b.jpg


Slightly wetted granulated r-candy mix:
(You can find my full own procedure here):
48135286778_9d24a8ed21_b.jpg

I used 70% demineralized water and 30% ethyl alcohol to facilitate the drying procedure. Few sprays of this mix should be enough.
Mix well the compond until it looks homogeneous. Do not wet too much or there will be issues during drying procedure.

A tea-spoon full of mix is the right mix quantity for every pressing step:
48135254711_79ec10977e_b.jpg


Starting to press the mix:
48135254576_d4600a3f63_b.jpg


The pressure applied is very high, about 5 tons (with my rammers diameter is equivalent to 8380 PSI):
48135254436_aef6b33965_b.jpg
I haven't noticed any performance boost exceeding this pressure. Besides this, I encountered difficult to extract the rammers
from the tube, so I do not suggest to exceed this limit.

The last press:


I created this special tool to make perfectly centered and parallel holes into the mix. Ball bearings was used to eliminate friction and wearings:
48135254146_18c248b838_b.jpg

48135285848_da3fc80f04_b.jpg


Aluminum tube inserted with perfect fit:
48135285698_610aaa83cc_b.jpg


Drilling the hole with a 12mm drill-bit:
48135285603_3f37b55b81_b.jpg

Please make sessions of max 2cm by time to avoid overheating the drill bit and allow the mix to come out.
I drilled tons of holes and I never had accidental mix ignitions, also in presence of titanium and with the drill bit really overheated, so it is a safe operation.
The ideal hole depth is 260mm to bring a 1300 grams shell to the right altitude.
Since these are conservative settings, You can add some extra thrust extending the tube lenght up to 350mm and extend the hole depth up to 310mm.
This extra lenght is useful for heavy double-petalled shells that weight up to 1600 grams

Hole drilled and pseudo-nozzle created with the help af a conical cutter:
48135253506_dd6ba7be73_b.jpg


Please do not waste the drilled mix: force it through a 20mesh sieve and add the powder to the classical granulated mix.
Since it is a very reactive mix, it can add a sort of boost to the original r-candy mix:
48135347767_3ecc327c2b_b.jpg


Drying the rocket with the help of a drying machine. Set the temperature at 70°C (158°F) and leave the rocket inside for an hour.
48135285153_4c47a551b8_b.jpg

Leave the rocket cool down (beware, the aluminum tube will be really hot!), re-drill the hole and put again the rocket inside the dryer for another hour.
Why? Well, the aluminum tube will not absorb the humidity, so a sort of r-candy syrup will escapes inside the hole and thru the hole, shrinking
a little bit the hole diameter. Re-drilling the hole will restore the original diameter (and You will earn some extra wetted mix, LOL).
 
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Minamoto Kobayashi

Well-known member
Joined
Aug 25, 2010
Messages
480
Points
63
Making some customs cardboard washers to arrange at the best the 6" shell on the top:
48135283353_7ccf954da0_b.jpg


Gluing the washers with Titebond glue:
48135285008_bc4264873f_b.jpg

48135284898_a3b1a2d732_b.jpg


Painting the washers edges with a tint similar to the gummed tape:


Rocket and washers wrapped with gummed tape:
48135284728_46ce35c547_b.jpg


Create a chamfer in the last washer to best accomodate the 6" shell:
48135345647_ec3a60bb4b_b.jpg


Making an hole at the center of the pressed mix to insert the fast fuse:
48135284523_873b8f99ef_b.jpg

Varying the depth of the hole will vary the ignition altitude.
Usually I made a 35mm mix thickness for the ignition delay at the top of the rocket, then I create 10mm hole depth, so the ignition happens after 25mm of mix.
Why do not make directly 25mm of mix delay? Well, first of all the internal pressure is noticeable, so a thinner delay could be insufficient to sustain that pressure and blow up with a dangerous premature shell ignition. Second, the hole will keep the fuse firmly in place.

Fast fuse inserted and locked with the help of a pressed cotton flap:
48135252556_5dcc90249a_b.jpg


Shell firmly glued with a lot of hot glue:
48135346752_f8bd6ef71c_b.jpg


2x1250mm long samba sticks was attached with hot glue to well counterbalance the rocket and to give a linear trajectory:
48135284118_f65ef9c3fb_b.jpg


In the past I suffered dangerous sticks detachments, so I wrapped both the sticks with 25mm gummed tape: in that way I lock
them firmly against the aluminum body:
48135284053_768e06ec14_b.jpg


A little reminder to quick recognise the kind of effect used inside the shell:
48135346442_a4de798da0_b.jpg


Creating a fast fuse joined to a 100 mm green slow fuse:
48135283763_e41ec210a4_b.jpg

The fast fuse lenght has the same lenght of the hole plus some millimeters. One extremity was bended so once inserted into the hole the bended part will grab well to the internal walls and it won't be able to get out again.
The fast fuse has a burn velocity of 1 meter/second, so it is ideal to ignite the hole walls at the same time along its entire length.

Inserting the fast fuse and lock then with a cotton flap:
48135251716_d8fa9f31b3_b.jpg

The cotton flap maintain the fuse centered and locked, while avoid that humidity can degrade the r-xcandy mix.

Finished rocket, ready to be lunched:
48135345947_c3f60db7fd_b.jpg
The total weight of this beauty is around 1800 grams.

My custom rocket launcher: a metal picket for umbrellas with a big aluminum tube inserted and firmly locked.
48135282983_89d285deae_b.jpg

If properly planted on the ground it will offer a solid launching base for my rockets.

As a bonus, You can download here a full 4K movie of another identical build with Kamuro stars:

That's all ... a couple of work! I hope You will enjoy my last effort

Richard.
 
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