ANAL chuffer

[Ralph]

Almost every time high power APCP rocketry comes up there is mention of ANAL which they said to avoid as it chuffs than a mention of once somebody made ANMG it was ok but they never did it again because APCP was for some reason better

 

what I want is to make a large(probably 2" id and probably ~15" long) cheap stationary chuffer. I understand the chuffing occurs as a pressure high enough to maintain a stable burn is simply unattainable. Also as I live in Australia many of the binders used in traditional ACPC are not available so something like common epoxy or even a traditional pyro binder would be great (ive noticed PVA seems to prevent Mg Nitrate reactions it may be suitable for this)

 

so my question is is there a cheap formula out there that anyone knows of that I can make to make a large stationary chuffer or is this just like boric acid (we find it everywhere like in gogetters supposedly protecting Mg despite the fact it makes it more dangerous and has just been added because of years of passing on vague information) also would changing the oxidiser to potassium nitrate or calcium nitrate be possible (They will not be quite as hydroscopic and are not likely to spontaneously catch fire)

[anapogeetoofar]

So, I'm assuming that you want to make an ammonium nitrate based "rocket" that will chuff throughout the burn, yes?

First of all, DO NOT use epoxy as a binder with AP or AN, trust me. HX-878 has NOTHING on epoxy when it comes to the volume ammonia released when mixed with AP or AN, some epoxy's aren't so bad, but most will damn near gas you.

Now, ANCP comes in all sorts of flavors: silicone based, HTPB based, neoprene based, and PVC based are the ones I have either witnessed working, or worked with. You also have ammonpulver like comps, but hat wont be of much use here.

Silicone based are very fast burning, ANISAL for example, has a burn rate coefficient similar to sugar propellants, not what you want.

HTPB based you cant get a hold of.

Which leaves Neoprene and PVC based, Both will work fine, but neoprene based is going to be the easiest by far in terms of preparation.

Start with something like 60-65% AN, 10-12% neoprene, 5-10% Al, 5-10% Mg, sulfur could be added to help with ignition (this is NOT easy to light though), tinker around with that and you should get something of use, but the problem you are going to run into is that it will be very difficult to keep the "chuffer" from blowing itself out, the only time I've seen a motor chuff ALL of its propellant away was when someone tried using RNX propellant in an aerotech case, so you could try that, but it will just be smoke, no flame.

Another problem is heat, this stuff burns HOT, it will be a challenge to keep a paper tube from being consumed.

If you don't mind a lack of flame, just go with KN/epoxy, though you might be able to add coarse Mg and Ti, maybe some sulfur.

Actually, that might be your best bet, 60% KnO3 10% Al or Mg 5% sulfur, 23% epoxy would be a good place to start, work from there. Maybe add some iron or Ti for sparkies.

Now I am assuming a "chuffer" is what you want and not a strobe.

Also, these are for the most part untested waters, be careful and experiment with due caution. If I'm on the right track here I could certainly dig up some notes and elaborate in greater detail, but I am have a hard time understanding exactly what you are looking for.

Oh, and don't bother with CaNO3, I tried doing all sorts of things with it, all I got out my hard work was puddles of water, a ruined scale, and many profanities.

 

Hopefully I was of some help!

[dagabu]

Man, I had an ANAL chuffer just last night. Even the dog ran away from me!

[WonderBoy]

HP rocketry is not my forte, so this is not an HP mix. I would recommend a standard BP rocket (or maybe nozzle less, I need to check my notes when I get home) with 5ish% mineral oil added. It gives a pretty nice chuff. There's a video of this in a 6lb motor somewhere, I'll try and locate it later.

 

Found it:

http://www.pyrobin.com/files/carley-6lb-chuffer.wmv

Edited February 20, 2011 by WonderBoy

[Ralph]

So, I'm assuming that you want to make an ammonium nitrate based "rocket" that will chuff throughout the burn, yes?

First of all, DO NOT use epoxy as a binder with AP or AN, trust me. HX-878 has NOTHING on epoxy when it comes to the volume ammonia released when mixed with AP or AN, some epoxy's aren't so bad, but most will damn near gas you.

Now, ANCP comes in all sorts of flavors: silicone based, HTPB based, neoprene based, and PVC based are the ones I have either witnessed working, or worked with. You also have ammonpulver like comps, but hat wont be of much use here.

Silicone based are very fast burning, ANISAL for example, has a burn rate coefficient similar to sugar propellants, not what you want.

HTPB based you cant get a hold of.

Which leaves Neoprene and PVC based, Both will work fine, but neoprene based is going to be the easiest by far in terms of preparation.

Start with something like 60-65% AN, 10-12% neoprene, 5-10% Al, 5-10% Mg, sulfur could be added to help with ignition (this is NOT easy to light though), tinker around with that and you should get something of use, but the problem you are going to run into is that it will be very difficult to keep the "chuffer" from blowing itself out, the only time I've seen a motor chuff ALL of its propellant away was when someone tried using RNX propellant in an aerotech case, so you could try that, but it will just be smoke, no flame.

Another problem is heat, this stuff burns HOT, it will be a challenge to keep a paper tube from being consumed.

If you don't mind a lack of flame, just go with KN/epoxy, though you might be able to add coarse Mg and Ti, maybe some sulfur.

Actually, that might be your best bet, 60% KnO3 10% Al or Mg 5% sulfur, 23% epoxy would be a good place to start, work from there. Maybe add some iron or Ti for sparkies.

Now I am assuming a "chuffer" is what you want and not a strobe.

Also, these are for the most part untested waters, be careful and experiment with due caution. If I'm on the right track here I could certainly dig up some notes and elaborate in greater detail, but I am have a hard time understanding exactly what you are looking for.

Oh, and don't bother with CaNO3, I tried doing all sorts of things with it, all I got out my hard work was puddles of water, a ruined scale, and many profanities.

 

Hopefully I was of some help!

 

Thanks for all the info Im just something with an irregular burn strobe or chuff would be fine just something to burn at our next shoot once we have set everything up and are waiting for daylight to go away. I think the epoxy fuel may be a bit to expensive (for a motor that is just going to sit upside down not really work getting 20 packets of epoxy) what formula would you sujest if PVC were to be used ?

Might try that two wonderboy looks good

[dagabu]

Ralph, why not use a strobe rocket (no booster) upside-down? They chuff nicely for quite a while. Red chuffers work nicely too.

[Ralph]

ANAL attracted me because it is cheap (AN$0.5/Kg Al $15-20/Kg) a strobe comp would be expensive so I just wouldn't bother making the stationary day time chuffer