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

[MinamotoKobayashi]

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://www.amateurpyro.com/forums/topic/13028-how-to-make-hot-granulated-r-candy-mix/

 

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 (as NeighborJ suggested me).

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 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:

 

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:

Edited December 18, 2018 by MinamotoKobayashi

[MinamotoKobayashi]

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:

https://www.youtube.com/watch?v=g_525R5vciw

 

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

https://www.youtube.com/watch?v=eWYL_dnbiPI

https://www.youtube.com/watch?v=wbkh9f9eHyc

 

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!

 

Edited December 17, 2018 by MinamotoKobayashi

[Nitrotitanite]

Great work, beautiful those parked rockets.

[dlking59]

Thank you for your great tutorials and a Merry Christmas to you too.

[hoangtuan]

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