Creating an ejection charge...

[blike]

I need to make a homemade CHEAP ejection charge for my rockets. I'd prefer not to have to buy any BP.

 

Yesterday I mixed KNO3 and Powdered charcoal 80/20. Then I made a small electric ignitor using a christmas light bulb. I packed the KNO3/Charcoal mix into a straw and put the light bulb in one end. Then I sealed both ends with hot glue and connected the lightbulb to a 9-volt. There was a small pop and the powder burned well. The pop was enough to eject the nosecone off a small estes rocket, but I'm sure it wouldn't be strong enough to push out a large nosecone with a camera on board.

 

What can I do to increase the *bang* without increasing the buck! The lightbulb, straw, and chemicals added up to something like 10 cents per charge.

[Gilded]

Hmm... If you have KNO3 and charcoal, then why should you even BUY black powder when you can make some yourself with some sulfur added (not too hard to get you know). I'd attach the nosecone so that it sits tight, yet there's only one critical part holding it to the rest of the rocket. This part should be easily replaceable, and made of something that would easily break with a small BP/thermite/something else charge. Perhaps there could be a small extra ejection charge after this, just in case. Not too costy, if you ask me.

[YT2095]

you don`t want to increase the "Bang", that may well split the body of the rocket

you need to increase the load (amount of powder) and therfore the volume of gas produced.

 

it`s NOT about BANG at all

 

 

edit: btw, have you considered my "tied back, loaded spring" idea, the one that`s a tied back spring in compression with fishing line around a visco fuse?

the fuse burns, melts the line and releases the spring, it couldn`t get any easier

[Gilded]

Ahh yes, if we are talking ejection only, lots of... ejection causing stuff is usually good. Perhaps you could even have a pressurized carbon dioxide ejection system, though that's probably going to cost quite a bit.

[YT2095]

CO2 charges are a min of 12.5g each, and that doesn`t factor in the cartridge weight and firing pin mechanism

 

he`de lose several 100 feet of Alt using that method

[Gilded]

Yeah, they indeed are quite heavy. :/ I'd still personally go with a small BP charge, in a critical point thereby de-attaching the nosecone.

[YT2095]

the BP charge is good, no doubt

 

I`ve used it myself on many an occasion, but the spring load and visco fuse is far superior in the way that the ejection is a 100% guarantee. AND there`s no burn damage or misfire risk.

 

both weigh roughly the same, except one is alot more reusable than the other

 

 

ok, it`s alot less Flashy (excuse the pun) but it Does work, and work WELL!

[RICHARDBATTY]

use a stronger container instead of a straw. reduce the volume to be filled when the container breaks. you could even try a piston in the container and have that conected to the nose.

[YT2095]

NO!

 

Bang is NOT good!!!!!!

 

gas volume is !

 

*WHOOOUUUMP* over *CRACK* any time with such a project.

we want a HEAVING charge, not Brissance.

 

the last thing he needs is a blown out front end and half a rocket! (

 

 

edited for spelling (and prolly still missed Some, LOL)

[Gilded]

"Bang is NOT good!!!!!!

 

gas volume is !"

 

Bang is especially not good when carrying rather expensive electronics, such as a video camera, aboard. Having your new thousand dollar cam blowing into tiny pieces because of too much *bang* isn't too nice. :|

[RICHARDBATTY]

no but a slightly higher velocity would help over come the drag on the cone and keep the weight down.

[Gilded]

That is true, but unnecessary (for example aluminum) shrapnels breaking your rocket casing are usually rather unwanted.

[RICHARDBATTY]

yes but a card cone with a bit of hot melt will last a fraction longer than a plastic straw.

[YT2095]

the charge can be wrapped loosely in peice of tissue paper!

 

there`s no "Velocity" needed!

[Gilded]

This rocket designing has started to seem veeery interesting to me. Perhaps a KNO3/sucrose rocket at first... Soon, I think I'll take my chances buying the smallest bag of KNO3 at our local gardening store has, and see if they go "OMG TERRORIST!" And I'll probably try the BP ejection charge too.

 

A dash off-topic: Hey YT, you're the grandmaster gardener here. What's the "code" of pure KNO3? You know, the one that tells the phosphorous values and so on.

[blike]

You can buy it as "Stump Remover" at most places. Check the back of the container and make sure. I just went to walmart and bought it from the gardening section. You'll probably want a coffee grinder to grind it down a bit more.

 

I'm going to see about building a light-weight spring ejection system based on YT's idea. I've never heard of anyone trying this method. I need to find some lightweight springs and mount it on a balsa or cardboard base. Hopefully the weight won't be too much of an issue if I'm using H and I class engines. I'll try and draw a schematic of YT's idea sometime tonight or tomorrow.

[Sayonara]

I just saw the title of this thread in "new posts" and had a mental image of you blasting off in a home made rocket.

 

Eject blike! Eject!

[ed84c]

Gilded is finnish and therfore has no walmart blike.

 

Ill post up my eperiments with KNO3 and sucrose and KNO3 and Coal dust as soon as i work out how.

[YT2095]

A dash off-topic: Hey YT, you're the grandmaster gardener here. What's the "code" of pure KNO3? You know, the one that tells the phosphorous values and so on.

do you mean the NPK ratio?

 

13.5-0-45 is the code

[q1werty2]

On 11/24/2004 at 9:04 AM, blike said:

I need to make a homemade CHEAP ejection charge for my rockets. I'd prefer not to have to buy any BP.

 

Yesterday I mixed KNO3 and Powdered charcoal 80/20. Then I made a small electric ignitor using a christmas light bulb. I packed the KNO3/Charcoal mix into a straw and put the light bulb in one end. Then I sealed both ends with hot glue and connected the lightbulb to a 9-volt. There was a small pop and the powder burned well. The pop was enough to eject the nosecone off a small estes rocket, but I'm sure it wouldn't be strong enough to push out a large nosecone with a camera on board.

 

What can I do to increase the *bang* without increasing the buck! The lightbulb, straw, and chemicals added up to something like 10 cents per charge.

You can easily get under 10 cents per charge.  I use Pyrodex P.  It is unregulated and a bottle will last years.  I assume you have an altimeter that will trigger the charge.  I use this methos for both the drogue chute at apogee and the main chute at 300 feet.

This is so simple, but it works.  I use a 1/2 cpvc endcap with a hole drilled in it.  I glued a holiday light (xmas light) receptacle in the hole and have it wired to the altimeter.  I then use the bulbs with the tip of the glass sniped off.  Insert bulb, fill with Pyrodex, then tape it up.

It doesn't yield a large "bang", but that is not what you are after.  It does generate enough expansion to pop the nose cone and shear the pins.

I have yet to have a failure.

Xavier