Black Powder Rockets

[ADP9]

Yes simple trig is the best way to calculate altitude. You must know how far away you are from the rocket and the only thing you must do is determine the angle with a proractor like device that d4j0n described above. With that angle, distance and the known 90 degree launch, one can use SOHCAHTOA trig and its simple. You could also incorporate the launch time to determine acceleration, speed, thrust, etc.

[justanotherpyro]

Yes these things I understand, but lets face it. There are a lot of people that are too lazy to mess with trig and want a practical way to approach the matter. Anyone who has done and work with sine cosine and tangent in 90 degree triangles could figure out the alititude, sure, but anyone can attatch some fishing line to the rocket and see how much of it came off the pulley

 

Yes it does work because its how I keep my rockets from flying. I have to test them in the city before I go anywhere else, so I basically tie them down to a log so I can test burn time, chance at CATOing and initial thrust. A very high tensile strength is a must though. Twine works well too, but is fairly heavy.

[ADP9]

Ha yes this I understand. Well then may I suggest kevlar fishing line. I've played with that stuff before and damn it's stong.

[leosedf]

Today i experimented with end burners...

12 of them all of them with 1cm internal diameter and a 3mm nozzle.

4 of the last ones where CATO, i think that's because of the 3-4 cm long core. It produced a lot of gasses for the 3mm nozzle so they exploded.

The others where just fine, but after they reached an altitude of 50-60 meters (some of them even more) they had the tendency to travel some distance (like a cruise missile) and i don't know why.

The engines started from 8cm long and reached 13cm long.

The long ones where still burning when hitting the ground.

[ActionTekJackson]

Odd... what's the ID on ur tubes? You sure the nozzle size is correct?

[d4j0n]

Odd, my 2oz end burners are exactly the opposite. I drilled 4mm into the grain and they took off rather sluggishly. Definately could not lift a payload. Also they kind of changed course in mid-flight but that may be from one of the sticks falling off, it was dark I couldn't tell.. Does the addition of 325 Al slow the fuel?

 

*edit, nevermind I see you are using a 3-4cm core. My question still stands though. I thought end burners should work fine with the core only a little bit into the propellant.

[al93535]

I never used a core in my end burners. I drilled into the clay until it barely hit the BP. Only one rocket did I drill a tiny core like 1/4" or so. They always worked pretty well. So yes, d4j0n, they should work fine. But it does depend on the quality, and speed of your meal BP.

 

The aluminum will actually increase the temp and the thrust of the rocket a little bit. But I never really got a tail from an end burner. I used up to about 10% 325 mesh atomized al.

[FrankRizzo]

End-burning rockets should use the hottest BP that you can make. Ideally, an indention in the grain of more than just a few mm should cause the rocket to CATO...they should be that close to the edge. A bit of whistle mix added to your sluggish BP can make a spectacular propellant.

[Exerd]

...The others where just fine, but after they reached an altitude of 50-60 meters (some of them even more) they had the tendency to travel some distance (like a cruise missile) and i don't know why.

The engines started from 8cm long and reached 13cm long.

The long ones where still burning when hitting the ground.

I'm assuming your saying that at higher speeds they are getting squirly and going sideways? Sounds to me like your rockets are becoming slightly unstable as they lost most of their forward weight during the burn. Did you use payloads in these or just motors?

 

The reason why I say unstable, is because if they were overstable and veered into the wind badly, you would more than likely see it happen right from ground level, as the higher they get the faster they go and it should happen less at altitude. Then again I guess I should ask you, were they all veering into the wind or just becoming unstable?

[Exerd]

End-burning rockets should use the hottest BP that you can make.  Ideally, an indention in the grain of more than just a few mm should cause the rocket to CATO...they should be that close to the edge.  A bit of whistle mix added to your sluggish BP can make a spectacular propellant.

This is what I say as well...run your motors hot and close to the limits!

 

You do benefit from higher efficiency and Isp (specific impulse) at higher pressures. The fuels simply decompose more completely in the reaction.

 

So in other words, a nozzle should be designed for the grain to run max pressure, with a slight safety overhead. If you have a nozzle big enough for a spike (small core) at the start, that when it gets to a strickly end-burning motor, the nozzle is then basically too large and pressure drops below desireable levels. Small cores are ok in bp, but not much of one at all. Unless that is, you do a full core and larger nozzle; these will scoot.

[d4j0n]

Is there a difference between hot and fast burning fuel?

 

Odd, I'm using alder bp milled for 5 hours with a harbor freight mill, the comp has 5% flake 325 mesh Al added and is granulated through a screen.

 

Is a 3/32" wide nozzle too big for a 2oz rocket? I'm stumped.

[leosedf]

...The others where just fine, but after they reached an altitude of 50-60 meters (some of them even more) they had the tendency to travel some distance (like a cruise missile) and i don't know why.

The engines started from 8cm long and reached 13cm long.

The long ones where still burning when hitting the ground.

I'm assuming your saying that at higher speeds they are getting squirly and going sideways? Sounds to me like your rockets are becoming slightly unstable as they lost most of their forward weight during the burn. Did you use payloads in these or just motors?

 

The reason why I say unstable, is because if they were overstable and veered into the wind badly, you would more than likely see it happen right from ground level, as the higher they get the faster they go and it should happen less at altitude. Then again I guess I should ask you, were they all veering into the wind or just becoming unstable?

They are just motors ( I am just testing).

All of them did take off pretty fast, when they reach a certain altitude then they go sideways and travel almost the same hight distance.

One of the rockets took off with a "snake motion" i could see it clearly, but i think that happens because i use short and heavy sticks.

Some of them made an elliptical motion and hit the ground pretty fast(still burning) but after they reached an altitude of at least 40-50 meters.

All of them whithout payloads and with a really fast and straight up take off.

 

 

I had CATO's when i drilled a 3cm and 4cm long cores.

[Exerd]

Is there a difference between hot and fast burning fuel?

 

Odd, I'm using alder bp milled for 5 hours with a harbor freight mill, the comp has 5% flake 325 mesh Al added and is granulated through a screen.

 

Is a 3/32" wide nozzle too big for a 2oz rocket? I'm stumped.

To answer your first question...yes and no.

 

There are of coarse different mixtures which may burn at much hotter temperatures than some (take thermite for instance), but this doesn't neccessarily have to do with how fast the comp will burn overall. It is simply a factor in the total equation. However, nearly any fuel-oxidizer reaction I can think of can be sped up by the addition of heat from a thermic agent, AKA Al/Mg. Too much Al/Mg though, and the density becomes so high that it acts as a heat sink effect...the heat cannot fully transfer in the short time period exposed and you will lose power.

 

Fast burning motors typically achieve these rates as a product of the combined micron sizes of the particles used. The smaller your combined micron sizes of compositions used, the faster it should burn, theoretically speaking.

 

To put it into perspective, think of the flame front which is occuring inside the motor. It doesn't contact the propellant as the burning reaction is happening (there is a smaller layer of gas products underneath the heat zone), but it comes very close. When you use larger granule size particles, this reaction front is displaced just ever so slightly farther away from the propellant during the reaction, thus lower the thermal conduction of heat into the propellant, and thus slowing the rate of the reaction.

 

Now when the particles are smaller, not only does the flame front get slightly closer to the propellant, but at any given time there is also more available surface area being exposed to take in this heat. This can be attributed to be the main factor in the burnrate equation.

 

Lastly we have pressure. Pressure forces the thermal conduction of heat into the propellant even more, and makes for a smaller (more dense) reaction zone, and also helps to consume any unreacted particles before they are ejected from the motor. It has been proven that if you take two motors, both of equal propellant weight, yet one is longer and skinnier, the longer one will be slightly more efficient (even though they cannot be compaired directly as they will have different burn times). This is due to the particles better reacting as they endure more heat transfer before they can eject the motor. This assumes a motor with a full core, not much as so for endburners.

 

As for the question about a 3/32" nozzle for a 2oz rocket...

 

I say one should only achieve his nozzle design from testing. No one else can verify a nozzles effectiveness by simply guessing, as none of us produce propellants that are identical. Close, but not identical.

 

I use KN value for all my motors. Calculate the surface area of burning propellant, and divide it by the nozzle hole area. This is your KN value. For an endburner this is simple because you are just figuring area of 2 circles and dividing. You can add 5% to the first value before dividing as it is known that endburners burn with a slight curvature in shape, like a miniscus on water only upside down. I work with AP motors and not blackpowder, but for reference I believe an Estes C motor has a KN of 25. If you run a faster propellant, try a lower KN value of coarse (not lower than 25 neccessarily, but lower than what you find to work for you). If you do it like this, with time you can develop KN's for all the propellants you design, thus knowing what will work when they are used.

 

Sorry to get into so much detail with this reply, but I think any design is best perfected when fully understood.

 

Hope this helps.

[Exerd]

They are just motors ( I am just testing).

All of them did take off pretty fast, when they reach a certain altitude then they go sideways and travel almost the same hight distance.

One of the rockets took off with a "snake motion" i could see it clearly, but i think that happens because i use short and heavy sticks.

Some of them made an elliptical motion and hit the ground pretty fast(still burning) but after they reached an altitude of at least 40-50 meters.

All of them whithout payloads and with a really fast and straight up take off.

 

 

I had CATO's when i drilled a 3cm and 4cm long cores.

Alright, they are understable it would seem. The snake action definitely clarifies this.

 

Use longer sticks simply. The payloads will help of coarse when used though.

 

As for the ones which went up, only to veer back into the ground, these are surely underpowered.

 

I had a few underpowered AP motors I made, they take off seemingly ok, but could not fight the wind strongly, and slowly curve until gravity is against them, thus plowing back into the ground. If they are not going fast enough, the stability effect is limited as drag is low, and is what allows them to become cruise missiles like this.

 

Your motors should have quite some coast time going up after they burn out, or else it would be apparent they are underpowered.

 

I would say you probably need a much faster propellant if you want the endburner design to be reliable with payloads. They need to force themselves skyward with some authority.

[leosedf]

They are just motors ( I am just testing).

All of them did take off pretty fast, when they reach a certain altitude then they go sideways and travel almost the same hight distance.

One of the rockets took off with a "snake motion" i could see it clearly, but i think that happens because i use short and heavy sticks.

Some of them made an elliptical motion and hit the ground pretty fast(still burning) but after they reached an altitude of at least 40-50 meters.

All of them whithout payloads and with a really fast and straight up take off.  

 

 

I had CATO's when i drilled a 3cm and 4cm long cores.

Alright, they are understable it would seem. The snake action definitely clarifies this.

 

Use longer sticks simply. The payloads will help of coarse when used though.

 

As for the ones which went up, only to veer back into the ground, these are surely underpowered.

 

I had a few underpowered AP motors I made, they take off seemingly ok, but could not fight the wind strongly, and slowly curve until gravity is against them, thus plowing back into the ground. If they are not going fast enough, the stability effect is limited as drag is low, and is what allows them to become cruise missiles like this.

 

Your motors should have quite some coast time going up after they burn out, or else it would be apparent they are underpowered.

 

I would say you probably need a much faster propellant if you want the endburner design to be reliable with payloads. They need to force themselves skyward with some authority.

I use standard BP (75:15:10) milled for 3-4 hours (seems pretty fine powder to me). Any suggestions??

 

 

-----------EDIT--------------

 

I also noticed that my kitty litter nozzle expands in the way. Meaning: It starts with 3mm nozzle and when it hits the ground the nozzle is aboun 4,5-5mm. Why?

[d4j0n]

I use standard BP (75:15:10) milled for 3-4 hours (seems pretty fine powder to me). Any suggestions??

 

 

-----------EDIT--------------

 

I also noticed that my kitty litter nozzle expands in the way. Meaning: It starts with 3mm nozzle and when it hits the ground the nozzle is aboun 4,5-5mm. Why?

 

It is the simple matter of erosion. Add about 33% grog or fireclay to your clay and it should prevent it.

 

I never used a core in my end burners. I drilled into the clay until it barely hit the BP. Only one rocket did I drill a tiny core like 1/4" or so. They always worked pretty well. So yes, d4j0n, they should work fine. But it does depend on the quality, and speed of your meal BP.

 

The aluminum will actually increase the temp and the thrust of the rocket a little bit. But I never really got a tail from an end burner. I used up to about 10% 325 mesh atomized al.

 

I have a feeling that the 325 flake Al has something to do with my rocket. I am going to try using plain bp now though from what I've just been told, the 325 flake Al should have in fact sped up the burn time. Maybe the stearin coating on the Al is causing a slowdown.

 

Just that it doesn't make sense why my propellant would require anything less accomidating than the standard rule of thirds rule and any kind of core (it IS an endburner after all). Yes I know there's variations from people's bp quality but I feel that mine is pretty standard. It's plain old alder bp put through the standard mill for 5 hours, this stuff should CATO with a core over a few mm.

 

Granulation doesn't count towards a larger particle size though right? The granules should be crushed instantly. Crystalization of the kno3 shouldn't really have happened as I dried the stuff immediately right after in our wonderful 113 degree F weather.

[leosedf]

It is the simple matter of erosion. Add about 33% grog or fireclay to your clay and it should prevent it.

I was thinking of fireclay myself but i didn't knew if it will work. I'll give it a try this weekend.

What is grog? Sorry for the question but my english is very bad

[TheSidewinder]

Grog as used in pyro applications is fractured, already fired, pottery clay. There's more than one type, I hear. You want to make sure to get the variety that's fractured (not milled or ground), and about 30 mesh.

 

Isn't "fireclay" just raw Bentonite? Or am I confusing that with something else?

 

M

[d4j0n]

Fireclay and grog are essentially the same thing, I forgot what the difference was though.

 

If you really want to be cheap you can crush up some floor or wall tiles, anything ceramic that has been fired already.

[leosedf]

What if i use fire resistand cement.

This stuff they use for ovens etc?

[TheSidewinder]

What if i use fire resistand cement.

This stuff they use for ovens etc?

 

Hmm... I thought THAT was fireclay.

 

Well, it might work. But really, grog is best.

 

Have you tried adding some graphite to your nozzle formula?

 

And, if you can get (ERROR*), that's supposed to be better than Bentonite for a base.

 

Good luck.

 

M

 

* EDIT: WHOOPS!! I meant Kyanite, NOT Gilsonite!

Kyanite (Aluminum Silicate) strengthens Bentonite nozzle mixes.

Gilsonite is Asphaltum, and won't be at ALL useful in a nozzle formula.

[Exerd]

Are you guys pressing all of these nozzle materials?

 

Does anyone use anything that's pourable?

 

Just curious, as I have not a press myself, thus I have been using phenolic bar. Looking for something more economical.

 

I hear quick cement (or quick crete?) and tilers grought are two choices for pourable, didn't know if there would be a difference, as grought seems like it would erode like crazy.

[d4j0n]

I just ram all my stuff. I too don't have the money for a press. Seems to work fine for me.

[leosedf]

Well..... I haven't tryed those formulas yet.

I'll try them this weekend (cause i'm in the city right now).

I only ram it, never tryed something pourable, i think it will be the same thing on those temperatures, it all depends on the material used.

[leosedf]

Yesterday i fired two small rockets.

 

One with a BP salute (I don't like flash powder) and one with some aqua stars.

 

The first is here http://www.youtube.com/watch?v=cbCE8UCLdWQ .

And the second is here http://www.youtube.com/watch?v=oe2wx7DQ1zc

 

Sorry no prefire pics.

The tubes had an ID of 14mm and where 12cm long, both of the payloads weight was 30gr. The star payload had a really crappy break but anyway.... One step at a time.

I'm still trying to find out a way to lift a new payload (90grams), maybe use a core burner?