Buzz Bomb/Helicopter devices

[deepdixie]

 

Hi everyone,

 

 

I am posting here as I need some advice from some of the more experienced pyros out there. I have been attempting to construct the ever popular buzz bomb/helicopter aerial spinner devices. I can't seem to get the propellant/fuel hot enough to lift each copter off the ground. Rather, they seem to just flop around on the ground after ignition.

 

My supplies are as follows:

 

-4 inch ½ ID parallel wound tubes

 

-Commerically produced helicopter wings

 

-Proper tooling, including Conical Cavity rammer.

 

-Bentonite Clay plugs

 

 

I have tried two different fuel types. The first is:

 

75% Potassium Nitrate (powdered)

 

15% Airfloat Charcoal

 

10% Sulfur

 

 

The Charcoal and Sulfur were balled milled together for two hours before being combined with the Potassium Nitrate and mixed by shaking in a plastic container. The mix was lightly moistened with a 50/50 mix of water and 70% Isopropol Alcohol before pushed thru a spaghetti strainer and allowed to dry in the sun for several hours on a sheet of aluminum foil.

 

 

The second fuel mix I used was:

 

60% Potassium Nitrate

 

30% Airfloat Charcoal

 

10% Sulfur

 

8% Titanium Flake

 

I followed the same procedures with this mix as the first mix I attempted. I hand rammed small increments of the dried fuel with a mallet on a ramming post. I drilled a 1/8 inch exhaust hole. The clay plugs worked as expected. Nearly every device ignited. A few flew several feet in the air before crashing. My guess is that I need to make some adjustments to the fuel mixture I am using. Most all the copters have spun on the ground. It seems they want to fly they are just lacking that little bit of extra power to become airborne. I would be delighted to see every device I build take off and fly a good 50 feet or more.

 

I believe I am very close to making this pyro project a success, but something small is lacking.

 

If anyone has any tips/critiques/pointers I would surely appreciate it.

 

 

[karliWadt]

Have you tried using rocket candy instead of BP? I've found if produced and cast correctly making a good fuel grain it seems to be far superior to BP. Harder to get right of course but when they work well they work really well! In a perfect world we'd all use hybrids and stuff but that can get expensive in both time and money!

[deepdixie]

Karliwadt, I haven't tried any other fuels than the two I listed above made from black powder. I have read about the rocket candy fuel and it seems like it is super powerful and might be worth a try. All the relevant literature I have acquired suggests that a 75/15/10 black powder mix is sufficient to propel these copters high into the sky. Thanks for your reply!

[karliWadt]

Also. Core burners or end burners? Makes quite a difference

[karliWadt]

Will definitely suffice to be honest. Best advice is to experiment with mixtures and see what works the best because impurities in chemicals as well as other environmental factors can effect the performance of your fuels. Rocket candy is definitely worth a try but as i said takes a little practice to get right. The first few times you'll probably end up with little smoke bombs not rockets. I know i did!

[deepdixie]

I would say that my more successful devices that actually attempted to fly were of the end burner variety due to the 75/15/10 composition. I am new to rocketry, aside from model rocketry that used purchased motors. Would there be any benefit to ball milling the Potassium Nitrate with the Fuels prior to pressing in the tubes? The PN I used is in Prilled form and I grind it to a fine powder with a Coffee grinder before mixing it with the ball milled fuels prior to hand mixing all 3 chemicals by shaking them in a plastic container. Do you recommend tweaking the 75/15/10 mixture to get a hotter/faster burn?

[Mumbles]

I don't think that RCandy would actually work all that well. RCandy, like BP and most other pyrotechnic compositions, burns faster under pressure. You really need a core to generate the initial pressure in order to get optimal performance out of it.

 

I think you would benefit by ball milling the composition. It clearly needs to be faster It would also benefit from the addition of some Meal. I've made a few of these, and used a variety of formulas with generally good success. I typically used meal with 10-25% added charcoal. This gives a better tail to the effect and tempers the mix a bit. The bigger the buzz-bomb, the slower of a mix you can use.

[Carbon796]

Helicopters should fly fine with a BP based fuel. Make sure the device is spinning the proper direction for the wing to produce lift. Also the wing ( especially commercial ones ) won't produce enough lift on their own to fly properly. The fuse hole should point downward at a 45* angle with the wing held horizontal.

[leedrill]

i take it the vent hole you have drilled is 45 degrees to the verticle on the tube have you tried just changing the angle a touch i mean 50 degrees will give you a fair bit more lift i have not made these before and am currently in the process of making some 1" id ones but everything ive read about them now they seem like they are going to be quite large approx 10" length 1" id 6mm vent hole and will have to play with that im sure i can down the vent to about 5mm if i need without having big ass crackers i will be pressing these due to the size ramming will not be sufficient as far as im concerned

 

are you able to share with me the size of the tooling and tubes you are using for my knowledge ? im mainly after the taper angle on the pointed rammer for {i am making my own} and have now seen 2 different angles being used im my opinion the divergence would help some what if the hole was drilled very precisely to the point and not just through the side wall of the taper of bentonite would like to try to help with your pursuit of these cool as things and would love help with my pursuit also of a 1"id version

[deepdixie]

Thanks to everyone for the replies. I have my vents angled at 45 degrees downward with the wings placed horizontal. I have detailed instructions that I purchased from a major pyro supplier. It seems that I am doing everything correctly. Yet the copters either fly briefly or completely flop around on the ground. Leedrill, the size of the tubes I am using are 1/2 inch ID X 4 inches long X 1/8 inch wall. I don't have the specific measurements on the tooling I used but I can provide you with a link to the retailer in your PM if you are interested. I have been reading everything I can get my hands on pertaining to the topic and believe that I would benefit from acquiring a solid wood dead blow type mallet for ramming the fuel instead of using the lightweight rubber headed mallet I am currently using. Edited September 1, 2013 by deepdixie

[Bobosan]

deepdixie, a dead blow or rawhide mallet will improve your grain consistency. Ram on a solid surface like a concrete patio that won't "give" as you ram.

Also, recommend drying your BP on something less reflective and heat absorbing.

[deepdixie]

Thanks Bobosan. I have been using a ramming post made from a wood fence corner post buried in the ground. My next move will be to acquire a dead blow mallet. Come to think of it, the wimpy rubber mallet I have been using probably isn't providing a stout enough blow to properly compress the fuel.

[Col]

Something else to try is to make the exhaust hole a little smaller, say 2.5mm or whatever the imperial equivalent is (7/64 maybe) It sounds like it just needs a bit more ummph at take-off. Edited September 1, 2013 by Col

[leedrill]

indeed either tune the vent or tune the fuel

[FlaMtnBkr]

From the few helicopters I have disassembled, they have all been end burners. Not real sure how you would make a core burner helicopter. Where the fuse is inserted may have been drilled a little deep to give a bit of a 'core' and give it a bit of an initial 'pop' to get going. Also, most end burners use pretty darn hot powder to give the device the energy needed. Some charcoal or metal can be added to give it sparks, but shouldn't slow down hot BP much. I would use 75-15-10 BP using a reactive charcoal like willow that has been well milled and granulated without a binder.

 

Also, I'm sure twisted blades help some but I think they add stability more than anything else. That said, make sure the vent is pushing in the right direction so that any benefit of the wings is in the right direction. The main lift is going to come from the vent being angled down as others have mentioned. I would try to find a commercial helicopter and copy it as much as possible. I believe there are quite a few projects listed in books such as Best of AFN series if you don't have access to a helicopter. I am stuck in a hospital and don't have acces to my books or pyro, or I would try to give you some basic dimensions to try.

 

Good luck.

[deepdixie]

Can anyone tell me if a steel based dead blow mallet encased in rubber would be safe for compressing rocket/helicopter motors? I'm thinking that as long as the outer rubber cover is intact there should be no issue with a spark hazard.

[leedrill]

i did this when i first started out with a normal hammer and i cut up an old gumboot and affixed it to the hammer but will be honest save your tooling and get an animal hide dead blow hammer like the ones wolter sells

[fyrcrack]

I just started fooling around with these myself. I will tell you what I have found out. Use a slightly fuel rich gunpowder mix. Say 65-20-15. Mill the nitrate and charcoal for 3-1/2 hrs. Add the Sulfur and mill for another `1/2 hr. This leaves only a half hour of dangerous milling time. Mix in an additional 2% dextrine and 5% FeTi or Ti or coarse charcoal. Don't mill it anymore after the additional ingredients are mixed in. Damp with water/alcohol 70/30 Use the 91% Isopropal Alcohal. Don't make it into a meatball. If you make it into a meatball that holds together, it is too wet. You want the comp so it just barely sticks together when pinched together between your fingers. Run it thru about a 12 mesh screen. This evenly distributes the water alcohol. Run it thru the 12 mesh screen again out onto a tray with 30-40 lb kraft paper. Do not dry in the direct sun light. Shouldn't take more than 12 hrs to dry. Don't put the tray near any flame source. It will be emitting alcohol fumes. Sorry this format will not let me start a new paragraph. Wing placement is very important. You need to place the wings 1-1/4" from the end of the tube, on the 4" long tubes. The nozzle hole is pretty small. I can't remember the diameter but it was less than an 1/8th inch. I know this method is a pain in the bum but unless you have access to 7F gunpowder it is necessary. Good Luck, Be Safe

[scubadoo2]

I've had problems in the past with nitrate leaching out into the kraft paper, .....Ned mentions this in one of his articles as well. Found plastic or aluminum foil a better media to dry BP on.

Wet and granulated makes it so much faster burning.

[deepdixie]

Fyrcrack, Do you completely dry your fuel before loading the tubes? Most of the literature I have acquired on helicopter devices says to load the fuel when it is still slightly damp then let the devices dry for up to 72 hours before use. I suspect that this method is used so that dust won't be an issue. I believe that I will try the 65-20-15 ratio that you listed. What if I ball mill all three ingredients together for four hours such as in making meal powder? I had previously only been milling the charcoal and sulfur together, then combining the two with the PN by shaking in a plastic container. Edited September 9, 2013 by deepdixie

[leedrill]

if you want more power then ball mill it and i really dont like the idea of loading a cardboard tube with damp comp i dont see a point to it at all

[fyrcrack]

Completely dry the comp. I did try a couple with slightly damp comp and they were slower.

[deepdixie]

After two different attempts at making copters with the 75/15/10 fuel mix using Airfloat Charcoal with very little success, I finally purchased some Black Willow Charcoal for use in the fuel. Nearly every formula that I have researched for these devices calls for the use of Airfloat Charcoal. I am very happy to report that every one of the copters from this latest batch using Black Willow has flown very well. Surely the hotter Charcoal is what made the difference, as it is the only thing that I changed. I used a small amount of 70/30 report comp with Titanium flake as a header.

 

I would like to get ahold of some higher quality Parallel wound tubes for use with the next batch of copters. A fellow pyro told me that the tubes that Hobby Horse sells would be a good choice, as the exhaust vent wouldn't have quite the erosion problem that a lower quality tube would. Can anyone verify this, or would it be a better bet to use a conical cavity rammer and place the vent hole through the clay plug where there would likely be no erosion at all?

[leedrill]

http://www.youtube.com/watch?v=teKea-mDdjc

 

http://www.youtube.com/watch?v=OUllmBGIBpQ

 

here are two of my 1" id buzz bombs the first vid is one 10" long with 60g of vitamins on the top the whole thing weighed just under 400g i staggered 15% Ti to iron granules i made two of them for new years and still can not figure out why the reports did not go {my theorey is the header got thrown off in the spin but i still think its unlikely }

 

the second vid is 1" id 7.5" long no header both with nept tubes from hobby horse and a conical cavity from my home made rammer 6mm vent hole in both you can see that the 15% ti and iron slowed down the mix significantly and you can see how the erosion is still a little bit of a factor not much but with both the cavity and those tubes you will be set to make some wicked copters

[Carbon796]

For helicopters, I use a rammer with a 45* bevel on the end, then drill through the clay at the pointed end. You can make an expedient one from a piece of oak or hard wood dowel pretty easy. Placing the vent hole through the clay plug will be more important than the quality of the tube. I don't use NEPT for helicopters, but it also wouldn't hurt to use them.