12 replies to this topic

[Pyro.1]

Small hummer inserts

KNO3 80
Charcoal (holly) 12
Sulfur 8
+ 2% Ti

Ground test (click for vid)



Paul.

[Sparky]

Very nice hummer. Did you make the tubes yourself? Where did you get the holly charcoal and how does the differ from willow or pine?

[Pyro.1]

Thanks Sparky, 50mm length 7mm id 12mm od 2.5mm wall, i have a few holly trees so the charcoal is home brew, it makes a lovely TT and is quite full of sparks, if i make bp with it there isnt much difference to comercial willow bp.
but it depends on what willow, i cook my own kilmarnok willow which i have growing as well, holly bp is not as good as Kilmarnoc bp.

Paul.

[bangkokpyro]

Lots of sparks but it doesn't realy hum does it. A good hummer makes a far louder buzzing sound than that.
The hole looks as if it's drilled in the center of the tube; it should be drilled tangentially so it emerges just on the top edge of the inside of the case and not the middle
Drilling the hole in this fashion gives the device it's spin and hence the noise. Straight meal with Titanium or a littel Charcoal will give added sparks

[cooperman435]

I was going to say the same, the unit spun end over end, whereas I thought a hummer spins along its axis so needs an "off centre" hole to give spinning thrust?

[Pyro.1]

'bangkokpyro', on 19 Nov 2012 - 12:28 PM, said:

Lots of sparks but it doesn't realy hum does it. A good hummer makes a far louder buzzing sound than that.

It isnt bad for such a small device

As the post sais, its a test lads , i tried a few different configurations with the 50mm and 7mm id, its a small device and isnt a loud Hum/Buzz but it does hum if you listen, iv also found with these tiny devices and Ti added the hum is much less pronounced no matter where you provide the vent, remove the Ti and its louder, add some FeTi and its inbetween. of course i could always go bigger but thats just defeating the object.

Phil
With this size and Ti its about the same spinning along the axis or around. the only difference is when i remove the Ti.

Cheers guys

Paul.

[cooperman435]

I disagree, spinning end over end will have unbalanced weighting from the burning of the composition and that's it's an un aerodynamic shape will prevent it reaching high rpm.

The hum comes from spinning on its axis, you need to drill across the edge of the tube not "directly into it" to create this effect

[Pyro.1]

The vent is drilled at around 60 deg, it isnt just a strait hole, the photo doesnt show it well.
i understand about the way these spin, i want the large spray and on axis doesnt give me that.
The Ti makes the difference with the sound, if i remove the Ti or use a finer grade at around 1% they buzz nicely but i dont get the large spray.

thanks for the comments guys.

Paul.

[Sparky]

Excuse the ignorance but isn't this effect used in shells, not exactly hummers but where you get a star that spins? I've seen a number of shells like this and I thought Pyro was deliberately going for that effect. They are more subtle, softer and with more white sparks.

Or are they all the same thing?

[pyromaniac303]

You're right Sparky, they're called Farfalle (Italian for 'butterflies' I believe).

[bangkokpyro]

Both Farfalle and Hummers (bees) can be used as inserts in shells (usually cylinder shells) but they are different effects.
Farfalle use longer tubes than Hummers and they don't make a buzzing noise. They also have the holes drilled straight through the tube in the center or in the end, sometimes both
instead of at an angle as in a hummer.
The comp used in Farfalle is not as fast burning as in a Hummer and produces more sparks and less thrust.
Any addition of Titanium, coarse Charcoal etc to the meal in a hummer of more than a couple of % causes a dramatic loss in noise and spin.
Hummers are also used to great effect in mines.

[Pyro.1]

Thanks guys , these are inserts for Shells/Rocket headers, i would of liked a bit more hum but they will do, its the real small size that is so restricting as its only a small amound of comp, so after all the tests i stuck with the ones you see in the vid, it gives the longest spin with a very nice Ti shower and a small amount of hum.

Paul.

[Mumbles]

I've gotten hummers of roughly this size to work just fine. From my experience, it looks like your vent is too large, and too close to the end. The effect you have is more like a tourbillon. Even tourbillons hum a little bit close up, but there is nothing audible from a shell break distance.