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Making very performant nozzleless r-candy rockets with my granulated mix.

Minamoto Kobayashi

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Hello forum.
As promised a lot of times ago here is a complete tutorial how to make performant r-candy rockets.
This kind of rocket is suitable to lift perfectly a 5" shell.
This tutorial follow my last one:

https://laserpointerforums.com/threads/how-to-make-hot-granulated-r-candy-mix.103345/#post1544813

This is a 25,5mm parallel wound cardboard tube with a wall thickness of 4,0mm and a length of 250mm:


The internal walls are waxed with a mix of 50% paraffin and 50% turpentine.
This mix has two main advantages:
1. Hot water is not necessary to melt the paraffin: with this mix a warm tap water is more than enough;
2. It is possible to make a thinner coating:


The cardboard tube is inserted in my homebuilt tool:


The tools is closed and strongly locked by a six allen screws:


Closing the bottom part. This little addon allow me to create an useful 15mm recess at the bottom of the rocket:


Filling the cardboard tube with my special granulated r-candy mix. Only one tea spoon at a time. This permit to compact the mix at the best:


Pressing the mix at about 4200 PSI with my modified hydraulic Fervi press:


This is the last step:


The carboard tube pressed and a brand new one: no deformations occured. This means that the waxing method worked fine and the pressure applied was ok:


A close-up of the recess:


For this kind of rocket, the hole lenght must be about 185mm and the remaining not drilled mix must be about 25mm.
The hole diameter must be 10mm.
These are conservative settings.
The top part (not drilled) should not to be shortened because the internal pressure could blow up the cap and cause a premature shell explosion.
If the mix is well made as described in my previous one tutorial and correctly pressed, the shell should explode just when the rokect has reached the max altitude:


Now, with another homemade tool, it is possible to make a perfectly centered and parallel-to-the-host hole:



When drilling the hole, it is important to proceed at little steps, 1-2 cm by time, to avoid drill bit overheating and the accumulation of ground powder inside.
Overturn the powder at each passage.
If the drill has many speeds, please select the lowest.
If the walls of the drilled mix produce too much friction against the drill bit blocking the drill rotation, it is possible to inject directly inside the hole a little spray of denhatured alcohol with the help of a siringue. Plase try to maintain the siringue as parallel as possible to the host.
This procedure act as a lubricant and everything works fine again.


The drilled hole:


And now it is time to make a beautiful pseudo-nozzle with the help of a countersink.
The max diameter of the tool fit perfectly inside the ID of the tube, so the cone will be centered and parallel:


The pseudo-nozzle will enhance the thrust:


The drilled mix burn fastest, so it will be saved and re-granulated in a dry form and mixed to the classical mix. This procedure enhance the overall performance of the compound:


The rocket will be cooked at 100 °C for 30 minutes inside a ventilated oven.
This step eliminate any residual of water/alcohol and make the pressed compound hard like a stone.
To avoid the dangerous radiant heat (a rocket that ignite inside an oven is the last thing that we want to see), two iron trays wil be placed between the rocket and the heating elements, so no direct heat will reach the rocket. Aluminum foils can be also used.


The tube is wrapped with a 25mm gummed tape:
 
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Minamoto Kobayashi

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Two homemade cardboard rings glued around the tube offer an excellent point of support for the 5" shell:


Creating a countersink around the ID of the last ring to perfectly accommodate the shell inside:


Painting the ugly white-ish cutted borders of the rings:
 

Minamoto Kobayashi

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Applying two stripes of gummed tape around the rings:


And now the fuses: a Visco superfast fuse (1 meter/second) and a green falling leaf slow fuse:


The ending part of the fast fuse was folded. When the fuse will be fully inserted, it will rest firmly in place because lock against the walls of the hole:


Joining the fuses with the help of a common paper tape:


Joined fuses:


Inserting the fast fuse until the end of the hole. The joined part must coincide to the end of the hole. Please be sure that no part of the slow fuse will be inserted into the hole, otherwise the rocket will be ignited from the bottom and shit will happen:


It is a good idea to press some cotton around the fuse. It will help to maintain the fuse centered and in place, and obstacle the humidity that can compromise the performance in a long term:


Gluing a 15mm x9mm x1250mm long stick:


This is a standalone rocket:

.. and this is the same rocket with a 5" shell on the top:

Well, that's all!
My second tutorial is complete.
Now I'm busy to prepare the new year arsenal:


.. but soon I will prepare the third tutorial "how to make perfect 5" shells" to complete the first saga

In the meanwhile I wish to all my faithful followers a warm merry Christmas and a happy new year!
 

RedCowboy

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Those look like great fun. (y)
Is that two halves of a 9 inch shell against the left wall ?
 

Minamoto Kobayashi

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Hi RedCowboy!
You are a careful observer LOL :sneaky:.
It is a 8" shell but it is my first attempt. It is massive, more than 2KG, and my main concern is to make a rocket able to lift
such weight!
The total weight (shell plus rocket plus 3 sticks) can reach 3KG total :censored:o_O
This is the lauch of an experimental 350mm rocket with aluminum body and for the momment is the only candidate:

 

RedCowboy

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Oh yea, you are having some fun. :)
Please share the video when you launch the big one too, even if it goes off a bit low it might look amazing.....that reminds me of the New Years fireworks at Stone Mountain, I used to climb the mountain the night of the show and find about 100 other people up there, the shells would explode at about eye level, it was very loud but awesome to see.

Here's a video it is not mine, but is shows what I was seeing, it's much better in person.

 
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paul1598419

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Very comprehensive tutorial, Minamoto. That is a lot of weight at 3 Kg to lift and accelerate to get it high enough to look good. Thyanks for sharing it all.
 

paul1598419

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Nobody is going to pay for someone else's thesis, that is ridiculous.
 

paul1598419

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I did too. Right before I posted about it. Seems it takes some time for the report to be seen and acted on.
 




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