Flying Fountain (New Firework - It works!)

[MrB]

The shell might actually make them more stable, because it would lower the center of gravity, acting like a guide stick on a normal rocket.

Rockets with a low center of gravity isn't stable at all. The stick is there to proportionally more the center of gravity forward.

(rocket without stick may have it's center of gravity just below the midwaypoint from top to bottom. Adding the stick moves the center of gravity further down the casing, but it also makes the rocket that much longer, making the center of gravity end up being well above the midwaypoint.)

 

Now, spin stabilized rockets don't use sticks, and adhere to a completely different magic. If you can get it to spin fast enough, anything is "stable". (Which is why stingers have that crazy spiral motion on takeoff, but straightens out as they spin up) Just not sure what speeds that would have to be. Oh, and stable means it wont go of in weird directions. It might still have a crazy wobble. Especially if it's not weighted properly, so it balances around the center of the rotation. It just might tear it self to bits. And as mentioned above, if you have to high spin, you might end up not being able to add effects to it.

It helps if you can spin it up before letting it take of...

B!

[BlueComet24]

Hmm... I was thinking that rocket sticks stabilize the rocket by moving the center of gravity below the nozzle, thus causing the thrust to "pull" on the center of gravity instead of "pushing" on it, which would be like balancing a weight, so unstable.

It sounds like these things spin so fast (enough to centrifuge charcoal to the walls of the tube) that it might affect the shell. I wonder if the centripetal force could actually make the stars go a bit farther?

A flying fountain with a shell could be loaded into a launcher, such as a short section of mortar the size of the shell. This way it would be able to spin up before launch.

[Mumbles]

I'd be interested in seeing how this works. If you test it out, let us know. I'd recommend starting with dummy shells. It's unclear how much lifting force these things have. Part of the thrust for these types of devices goes into spinning, not just lifting.

 

The stars will probably be thrown out a little bit. If you watch some of the girandola videos on youtube you can see this to a lesser extent. The tails mke a nice christmas tree shape or spiral on the way up, and the softer broken inserts kind of splash outwards. Check out some of the ones by Tom Dimock or Tony Stader. They're simply works of art.

[MrB]

Hmm... I was thinking that rocket sticks stabilize the rocket by moving the center of gravity below the nozzle, thus causing the thrust to "pull" on the center of gravity instead of "pushing" on it, which would be like balancing a weight, so unstable.

 

Stick rocketry is a fairly stable method of flight, even if the rocket them selfs are quite unstable. The principle is that you have a heavy mass, with comparatively low drag, moving through the air. On it's own, it would tend to tumble, and thats why the stick is added. The stick adds very little weight, but a lot of surface area, which when moving through the air, generates drag. If the rocket starts to "tumble" (it never gets very far) the side of the stick is exposed, causing a lot of drag, and quickly the rocket corrects back. This is why crocked sticks generate weird bent flight-paths. The stick simply places the rocket in the "least" drag inducing position, and if the engine points away from the centerline, it makes an arch. In reality even a perfectly straight stick causes a small arching trajectory, since the thrust and the weight of the stick isn't in line with one and other, but we generally don't care, it's rather tiny.

 

 

A flying fountain with a shell could be loaded into a launcher, such as a short section of mortar the size of the shell. This way it would be able to spin up before launch.

 

Not sure if this would work. If the mortar is "to close" to the size of the unit, it's going to reflect the thrust of the walls, and on to the darn thing, creating an equal force to counter the lift, leaving it, at best, spinning in the tube. And if it's large enough to let it act as freestanding on the ground, it's going to take of as soon as the lift is enough, regardless of the spin. It's speculation at best, so trial and error would make it a known.

 

 

The stars will probably be thrown out a little bit. If you watch some of the girandola videos on youtube you can see this to a lesser extent. The tails mke a nice christmas tree shape or spiral on the way up, and the softer broken inserts kind of splash outwards. Check out some of the ones by Tom Dimock or Tony Stader. They're simply works of art.

 

I've been putting shells on stingers for ages, and to be honest i don't see any difference between the same shell shot from a mortar, on a stick-rocket, or a stinger. I think the reason simply is that the shell is to close to the rotational center. Shot from one of these, or from a stinger, that "should" remain the same. But again, guesswork.

B!

[BlueComet24]

Mumbles, unfortunately I won't be able to test one of these anytime soon. I'm currently working on perfecting my BP and 1.75" shells and I haven't gotten a chance yet to test my second ever 4oz BP motor (the first one had a semi-CATO). The closest I've made reliably are 1/4" BP rockets, and I doubt I could easily modify one to work as a flying fountain. I'm on winter break now, so I can fully resume my pyro activities. I was hoping that usapyro could test my idea, but it seems that he hasn't been seen in a few years.

 

B, thanks for the explanation. That makes sense now.

I was thinking of a very short mortar, only tall enough to house the shell so that the thrust goes outward. However, you're right that it wouldn't really help it to spin up before takeoff. Maybe it would be possible to put the flying fountain over a screw eye sunk flush into a board with a string attached to it and have the spinning of the motor unwind it and release it. I'm not sure how something like this could be done without metal like a butterfly bomb fuze: https://en.wikipedia.org/wiki/Butterfly_Bomb

[FlaMtnBkr]

Here is my thought since the spin is so fast as to pin any sparking material to the walls.

 

Press in a flat clay end plug. Then press in an increment or two of slow fuel. This section will have one or two tangential vents drilled in horizontally to spin it up without lift. Then a tapered clay nozzle is pressed on like USApyro did. However, the very tip will have a small diameter tit added to create a small passfire hole. I have never used a ram with a tit though they do exist so must work. After ramming the tapered clay you may need to take a small drill bit and insert it in the passfire hole and gently twist with your fingers to clean out and clay. Then press the increments of fuel to fill the cavity and the passfire hole. Then drill downward angled vents like USApyro described but with no offset and finish like he described.

 

The device is then placed in a short tube and the top most horizontal vent is fused and lit. This will allow it to spin up and stay on the ground spinning in the launch tube. It will then start to slow down as the fuel burns down the password hole and eventually starts to exit the downward vents providing lift but no spin. If the passfire hole is small, a little thrust will exit the horizontal vent so the spin is hopefully maintained at the slower spin but not increase much.

 

You could also just have a nozzled core burner section but it seems the main goal is to spray sparks outward and that wouldn't happen. You would also just have a stinger rocket.

 

I imagine it would take some tweaking with nozzle diameters and fuel burn rates but wouldn't be much more complicated than the original design.

 

It also doesn't seem like a high pressure design. You may be able to roll your own tubes using sodium silicate or a high percentage of it mixed with another glue, maybe a better wood glue, to give it more tack. I've never tried this but if it can substantially fire proof the tube you may get away with not using the complicated clay plug. Has anyone rolled tubes with waterglass and does it really help with burning and nozzle erosion in a stinger?

 

Just what came to me while reading the thread and the problems.

[usapyro]

I recently developed a much simpler improved way to make these allowing you to use your effect fuels with full effects! For new people who have not seen this firework, simple goto youtube.com/usapyro. Finally, these now work perfect!

 

 

Just custom roll a double normal thickness tube. Do not use a internal clay nozzle! You will get a great effect with lots of sparks. Sure, it might erode and burn the paper a bit during flight, but as it burns it's getting lighter so it negates the lost thrust a bit. Also, the nozzle goes a long ways through the paper because you drill near the side of the rocket at an angle. This way of doing them is also much simpler.

 

 

The amount of centrifical force generated in these Flying Fountains prevents sparks from properly reaching the nozzles in the prior design, because they couldn't battle their way uphill into the nozzle. This reduced your spark effects from the main grain to nearly nothing at high spin speeds (Be it added Charcoal, FeTi, etc...). But, the sparks can make their way to the nozzle bouncing along the sidewall just fine under quite a lot of centrifical force.

 

If you have done this new design right and have your nozzles properly opposite each other and drilled with a guide... Once the burn hits the hot grain it will take off perfectly and consistently just from sitting on the pavement.

 

Oh, and POST VIDEO's of yours here so I can see them! I will try to get a video up sometime. You only need one new tool to make these... A drill guide. Can be made out of a few pieces of wood in a few minutes. A simple way to make a drill guide:

 

http://i48.tinypic.com/2416m3q.jpg

 

For the new design, you only need the small side drill guide to guide the drillbit into the rocket at a identical angle and offset on opposite sides.

 

Yea, the rotation speed on that one was ridiculous... I am half suspicious it rotated so fast it cracked the grain! Jk, but far more rotation than required! Remember this... The more offset you can put the nozzles the better the rotation stability. The more angled the nozzles the less rotation stability and the more forward thrust. The happy balance is likely around fifty degrees. That dedicates most energy to thrust but still has enough going to rotation and pushing sparks outward.

For an extra straight launch you can probably launch them out of a short tube that is half the length of the rocket. Shouldn't be needed though. There is a trick to the stable launch. Ram a delay fuel inside the internal nozzle so there is no thrust before it hits the main grain. If you put a fast fuel in the internal nozzle area it might tip it over.

Also, one little thing to help you with the nozzles... They are actually longer than my side view drawing makes them appear. This top view give you a better idea. I intersect the side of the internal nozzle with the exit nozzles. I also have some makeshift tooling I created for ease in making these. A large drillbit with a depth stopper and a tool for drilling the nozzles perfectly.
http://i48.tinypic.com/20hvtk6.jpg
Here is a better side view...
http://i46.tinypic.com/4icu8m.png

Edited June 30, 2017 by usapyro

[dynomike1]

Since i dont have time to work on this, i will recommend a cool effect. If you could start it up then stop for maybe 20ms then up again then stop with sparks still coming out. I guess changing comps would be the way to do it.

[lloyd]

Mike,

That's not a new principle, although it might be attractive. Gyrandola makers put 'pauses' in the thrust all the time, to get the Gyro to rise, drop, rise, etc.

 

LLoyd

[dynomike1]

yea the wind made 1 of mine do that.