problem kno3/sugar rocket

[THEONE]

When you are using rcandy, and you are using a clay nozzle end plug, how after you rammed the end... if you ram it your rcandy grain will brake...

[donperry]

You can do one of two things.

 

1. Form the nozzle by ramming the clay, cook the candy, compress the hot candy with dowel and let it cool, then ram bulkhead. Then drill. Cracks may develop if you are not careful here. Let it cool a bit, but not too cool where it starts to harden. [my recent rockets built this way].

or

2. Form nozzle with clay. Cook a brittle candy. That is, use normal white sugar and KNo3.

Let it cool and harder (snap test?), then beat it to a dust or grate it to a dust.

Doesn't have to be fine dust as you will ram it

 

that rCandy dust will be ram-able unlike the one in the first option. Hot Candy cannot be compressed as easily as this one.

 

If you have a grater or a mortar and pestle them the second option i recommend.

Edited April 26, 2011 by donperry

[THEONE]

OK thanks donperry

 

Today i made a motor with 6.5mm throat, 17cm long 3/4 inch pvc pipe 3 rcandy grains

Then the motor start to burn... i notice that sometimes the gases stops to comes out, something like stuff the nozzle and dont let the gases escape. this were happens 3-4 times after the nozzle blow out out and the last grain was into the motor without burn !!!

why all these happens ?

Edited April 27, 2011 by THEONE

[Mumbles]

It's called chuffing. Often times it is indicative of a poor oxidizer:fuel ratio. Your nozzle is a fine size, if even on the larger end of the spectrum.

[THEONE]

It's called chuffing. Often times it is indicative of a poor oxidizer:fuel ratio. Your nozzle is a fine size, if even on the larger end of the spectrum.

 

Mumbles can you to explain to me little better because i didnt understand ? also my English are not the best... so how i can avoid this ?

[Mumbles]

I can't tell you for sure. The clogging and unclogging is something called "chuffing". It happens when there is too much liquid or solid product formed inside the rocket. Ideally you want everything to be a gas, or at least a fine powder. It usually only happens with a bad mix of KNO3 to sugar. I may also happen if your fuel has absorbed water. You could try changing your ratio, or making sure you make it right. The other cause is too small of a nozzle opening, but that doesn't seem to be the case for you.

[donperry]

Be sure that your candy is neither overcooked nor undercooked. It is ready when the hissing stops. At that point turn the flame really low. Take a sample, let it cook a bit and roll a test strand. If it burns ok you know its ready.

If it is undercooked and still has water it will chuff.

 

If it is overcooked it means you have started to decompose the fuel and the burn rate will suffer.

Edited April 27, 2011 by donperry

[THEONE]

So the problem is the fuel, i was playing for a ratios to make a rcandy burns about 10sec per inch but maybe i put wrong ratios, here we haven't got Caro syrup... so i use glucose...

I tried knsu 65/35 rcandy but it was very fast... about 6sec per inch.... it was very fast for a core burner rocket... how can i reduce the burning speed ?

Edited April 28, 2011 by THEONE

[donperry]

You can cook it a little longer. I'd also use less kno3.

 

Did someone say baking soda? I have baking soda popped in my head but i canr remember if it works in this mix.

[Mumbles]

I would worry about making functional rockets before worrying about the fuel and other fine tuning things.

[THEONE]

OK boys, the correct ratio is 64/36 kno3/sugar as wikipedia says.

I found a syrup of fructose glucose were say that 125gr syrup are about 100gr sugar so 10gr syrup equal to 8gr sugar so in ratio 64/36 -->64gr-kno3 / 28gr-sugar / 10gr-syrup...

And it were worked OK, round 8.5sec/inch...

After i make a motor with this fuel... but i had the same results... chuffing again... and the nozzle blow out...

The motor had 6.5mm cement nozzle throat (steal washer) ...

The fuel was the previous one...

13cm core length 5mm diameter...

end plug 3cm cement with 2 screw all the way...

 

Here some photos for the nozzle were i am going to put and the motor from above were the nozzle blow out,and i am going to reuse it

I glue them together with PVC glue (plastic pipe cement)

Edited April 29, 2011 by THEONE

[THEONE]

It is possible that the chuffing cames because of the inhibitor sleeve burns and it comes out ... so it stuffs the nozzle...

I mad a inhibitor sleeve from paper...

Edited April 29, 2011 by THEONE

[donperry]

ok.

your nozzle looks a bit small tho.

Edited April 29, 2011 by donperry

[THEONE]

ok.

your nozzle looks a bit small tho.

 

I don't think so, it is 6,5mm...

Dan Pollino said that this it is happens because i ignite the motor near to the nozzle, the motor must be ignite from the top, near the top plug...

[donperry]

Do you have black powder?

 

My fuses are now laced with BP at the head. What i do is make some paper fuse (which doesn't really light rCandy that easily, but it can) and then at the top i add some BP and tape it around

once it burns up and travels up the core the BP will ignite and the motor be ignited near the top

 

I've never had chuffing lighting from the bottom.

 

also, ur nozzle diameter should be 1/3 of the motor diameter.

 

if that is a 1 inch rocket then 6.5mm is waaay too small.

 

If 1 inch you need 3/8 of an inch nozzle. Thats the lower limit, no smaller than that for my fuels.

And with PVC is better to be too big than too small, or else you wouldn't have a rocket but

a pipe bomb

Edited April 30, 2011 by donperry

[THEONE]

Do you have black powder?

 

My fuses are now laced with BP at the head. What i do is make some paper fuse (which doesn't really light rCandy that easily, but it can) and then at the top i add some BP and tape it around

once it burns up and travels up the core the BP will ignite and the motor be ignited near the top

 

I've never had chuffing lighting from the bottom.

 

also, ur nozzle diameter should be 1/3 of the motor diameter.

 

if that is a 1 inch rocket then 6.5mm is waaay too small.

 

If 1 inch you need 3/8 of an inch nozzle. Thats the lower limit, no smaller than that for my fuels.

And with PVC is better to be too big than too small, or else you wouldn't have a rocket but

a pipe bomb

No i haven't BP but i can make...

 

My ID of my PVC pipe is 21mm...

Also does somebody know that glue i must use to connect the coupler with the pvc pipe ?

I use a Duro Stick pvc glue (plastic pipe cement) and it say that it can accept until 12atm after 24ours dryness...

It is like this one but in the tube.... it was very cheap 1.50€ i think it is not good enough... What you think boys...

Edited April 30, 2011 by THEONE

[donperry]

hmm. thats strange. THe ID of my 1 inch pvc is 25mm something

 

anyhow, if it is 21 then 6.5 is just a brush under the 1/3 diameter. If you get blowouts increase this diameter.

 

I sent you the PDF

Edited April 30, 2011 by donperry

[THEONE]

*e-mail removed* add me to g chat

 

OK donperry i have already send you an invitation...

This PDF i have it already....

The PVC pipe were i use is 3/4 inch, no 1 inch, like

Edited May 2, 2011 by Mumbles

[moondogman]

Damn i would quit now.

 

If my first sugar rockets hadnt flown id be several hundred dollars richer than I am now.

 

Steve

 

 

[donperry]

lol ^^^ Sooooo true

[MadMax]

That hole looks a bit small. Depending on the material you used the nozzle may be getting gummed up rather then allowing the solid particles to pass through. It needs to be hard and smooth like those that are pressed under tons of force. The nozzle should be tapered on both sides to funnel gasses in and out.

 

I would test the rcandy too. If you burn a piece it should burn fast and leave no solids behind.

[THEONE]

Damn i would quit now.

 

If my first sugar rockets hadnt flown id be several hundred dollars richer than I am now.

 

Steve

 

What do you mean ?

 

That hole looks a bit small. Depending on the material you used the nozzle may be getting gummed up rather then allowing the solid particles to pass through. It needs to be hard and smooth like those that are pressed under tons of force. The nozzle should be tapered on both sides to funnel gasses in and out.

 

I would test the rcandy too. If you burn a piece it should burn fast and leave no solids behind.

I have seen many many videos like

and this one that they doesnt have conical entrance and they are bigger motors too!!

My rcandy doesnt leave something, i recrystallized it...

Edited May 3, 2011 by THEONE

[donperry]

OK> You listen and listen well.

If you want to survive this hobby and not waste money you WILL HAVE TO listen to other members that have done it before and are sharing experience with you.

 

For the last time

 

#1 Nozzle too tiny

#2 Start with regualr fuel mix

#3 Avoid PVC

#4 Avoid extra long rocket cores

 

And when you have your first flight come back and tell us about it!

[Mumbles]

Those videos do very clearly show exit cones though. It's better than nothing as it will help to funnel the gases out via a syphon type effect.

 

If you want to learn how to make higher powered rockets, I'd suggest a different forum. We typically use a different design for different purposes. The people here will not be able to help you as much as some others. If you want to continue here, you should probably drop the whole PVC thing.

[THEONE]

OK> You listen and listen well.

If you want to survive this hobby and not waste money you WILL HAVE TO listen to other members that have done it before and are sharing experience with you.

 

For the last time

 

#1 Nozzle too tiny

#2 Start with regualr fuel mix

#3 Avoid PVC

#4 Avoid extra long rocket cores

 

And when you have your first flight come back and tell us about it!

 

I already have a successful flight in my no1 page

The nozzle diametre and the core length depents also from the fuel

 

And relax my friend, it doesn't need to scream...

 

Those videos do very clearly show exit cones though. It's better than nothing as it will help to funnel the gases out via a syphon type effect.

 

If you want to learn how to make higher powered rockets, I'd suggest a different forum. We typically use a different design for different purposes. The people here will not be able to help you as much as some others. If you want to continue here, you should probably drop the whole PVC thing.

 

 

Yes i know, and i also have exit cones though at my nozzle.

 

Mumbles i saw some people here that they use PVC as a casing so i thought that they could help me, the more we know about the subject the better it will be...

 

But Mumbles you are the Admin... you can judge and if you don't agree, you can just lock the topic.

Edited May 5, 2011 by THEONE