Mixer Posted June 9, 2016 Posted June 9, 2016 (edited) Here`s some info for anyone wanting to make Speedballs/Zippers/Zips they`re great fun, quick to make, and take very little comp. If you duplicate these specs you will be able to make them consistently perform as good as or even better than those shown in my earlier post. For the tubes the Kraft paper strip is coated both sides with thinned Sodium Silicate solution (waterglass) - this step is quite important as it reduces the side hole erosion by around 35% (without it the hole erosion is unacceptable and reduces the sound) You don`t have to completely coat all surfaces, I just find it quicker this way. When dry they are pasted and rolled. The following are the specs that gave me the best results after a few weeks of testing. Tube length 39mm. (1.5") Tube internal diameter 8mm. (0.3") Tube wall thickness 2.4mm. (0.09") Total spindle length 24.5mm (0.96") with a 1 degree taper towards the tip. Choke Dia. 1.7mm. (0.067") Choke clay depth is strictly 4mm. (0.16") Bulkhead clay depth is 6mm. (0.24") Choke and comp pressed at around 2000psi. The tube side vent hole of 1.76mm (0.07") is pre-drilled tangentially a few mm above the tip of the spindle for insertion of a thin piece of black match retained with a dab of nc/bp mix or similar. If the units are to be used for garnitures then the side hole vent can be drilled just above the clay choke like a stinger missile - they will work just as well - a little rolled paper inserted in the choke end covered with a small piece of masking tape will prevent premature motor ignition. I use a basic rocket mix throughout, dampened and granulated through a fine mesh sieve and dried for a little extra power. Potassium nitrate >100# 70 H`wood charcoal (airfloat) 20 Sulphur 10 Atomised aluminium 350# 2 60/30/10 and 65/25/10 also work well, but the above formula has the edge. The spindle measurements given are fairly critical but you can change them providing you keep within a KN value of around 100 -115 which will ensure the best results. The units can be scaled up but you need to keep a close eye on the KN value. Anything under 100KN is not so good, over 120KN and it may well blow the choke/bulkhead out or CATO. To find you approx KN value divide your core length max burning area by your total choke + vent hole area. Example below. Core length 20.5mm x Internal diameter 8mm x 3.14 = 514.96 Max burning area. Choke spindle of 1.7mm/2 = .85 x .85 = .772 x 3.14 =2.26 Vent hole of 1.76mm/2 = .88 x .88 = .774 x 3.14 = 2.43 ....514.96/4.69 = 109.79KN. Be careful, they can zip off in unpredictable directions. Just ask if you need any help. Edited June 9, 2016 by Mixer 1
memo Posted June 9, 2016 Posted June 9, 2016 you gave me a idea, go getter tubes and tooling should work, going to give it a try. memo
dagabu Posted June 16, 2016 Posted June 16, 2016 Mixer, I am up-scaling these for use with 24.5mm ID tubes and just have one question, when you wrote, "The tube side vent hole of 1.76mm (0.07") is pre-drilled tangentially a few mm above the tip of the spindle...", is the distance above the spindle consistent or is it a matter of taste? I am finishing a drilling jig and want to be consistent.
Mixer Posted June 16, 2016 Author Posted June 16, 2016 (edited) `Just a matter of taste` It isn`t critical at all. 24.5mm! Hmm, I think I`d get a long way away from that when you light it!! Edited June 16, 2016 by Mixer
dagabu Posted June 16, 2016 Posted June 16, 2016 I agree! these will weigh about 200g when fired and will have a 10g report if all goes well. I'm planning on testing them from a barge in the lake with a firing system so we will be far out of the way if something goes wrong.
OldMarine Posted June 17, 2016 Posted June 17, 2016 I agree! these will weigh about 200g when fired and will have a 10g report if all goes well. I'm planning on testing them from a barge in the lake with a firing system so we will be far out of the way if something goes wrong. I had a buddy who told me they were going to fire a bunch of fireworks from a boat anchored in the middle of a lake on their farm. The next day his wife called me from the hospital.Yup,you guessed it, he went out on the boat with them.
dagabu Posted June 17, 2016 Posted June 17, 2016 Lol! I get to use an old flat top pontoon boat. I'll be on shore about 1000' away.
Mixer Posted June 17, 2016 Author Posted June 17, 2016 (edited) What Kn value do you have? Edited June 17, 2016 by Mixer
dagabu Posted June 17, 2016 Posted June 17, 2016 Mixer, that is what this test (static, in a stand) today will determine. I haven't done the math on the Kn value yet but the 24.5mm tube will fly on this spindle with a clay choke. For those that want to do the math, the spindle is 2.5" long and .33" diameter. Nozzle is .33" and the vent is .33" as well.
ddewees Posted June 17, 2016 Posted June 17, 2016 My money`s on a CATO! I prefer Elon Musk's term RUD... "Rapid Unscheduled Disassembly" 1
Mixer Posted June 17, 2016 Author Posted June 17, 2016 (edited) I spoke too soon - I should have done the math - your Kn value is very low - it may not even take off The reason these things are so effective is their size, power, and the mass is very low, giving very rapid spin up. This is why they are kept small. Edited June 17, 2016 by Mixer
dagabu Posted June 17, 2016 Posted June 17, 2016 (edited) Mixer, This is the beauty of experimenting, we really don't know if it will undergo RUD or fly or sit and spit. The BP I am using is extremely hot and may undergo RUD no matter the vent size, I will see... I have made hundreds of Z-bombs and hummers (perhaps thousands of hummers) and always use the same methodology in dialing them in. 1. Start with HOT BP, RUD them if I can, my hummers did not so I added 10% benny whistle to get them to undergo RUD. 2. Add 10% charcoal to the mix and try again, add another 5% charcoal until they fly with no failures.3. Add up to 5% metals for tails and bump the charcoal down 2% to compensate. I write the comp ratio and metals on the jig along with the tube length so I can easily replicate the effect. This works well for me. Edited June 17, 2016 by dagabu
Mixer Posted June 17, 2016 Author Posted June 17, 2016 Yes, that`s a perfectly feasible way to arrive at an acceptable finished product. This is pretty much what I did with my development, but of course knowing the ball park figure for KN value beforehand was an enormous help - which saved me a lot of time and trouble. The Tutorial is for those who want proven results without all the R&D which could entail without it.
dagabu Posted June 17, 2016 Posted June 17, 2016 BUT... the tut is for small zippers, for those that want to scale it up, this might be helpful to them.
NeighborJ Posted July 28, 2016 Posted July 28, 2016 These zippers are awesome, I had experimented with them a few months ago only they didn't have a nozzle. I was able to use the hottest powder I had and did not need to reinforce the spinner nozzle due to the short burn time. As with most projects I super-sized these things with a 6# version. I did need to make a shorty version to ensure the spinning motor stood vertical. The casings only needed to be 5" long. At some future time I'd like to revisit this project to see if I can fasten some sort of effect other than a salute.
dagabu Posted July 28, 2016 Posted July 28, 2016 I have a dozen tubes drilled and cut for testing at PGI, I will be pressing them tomorrow but need to cut my BP by 30% to keep them from popping.
memo Posted July 28, 2016 Posted July 28, 2016 (edited) hell i am at 90% popping. but the one that worked was very cool. I am using straight out of the mill powder with 10% by weight ti. even pretty when it pops Edited July 28, 2016 by memo
NeighborJ Posted July 28, 2016 Posted July 28, 2016 I've never had one pop after making them nozzleless but I did learn that the header needed to be at least 1/2 dia thick or it will sort of fall apart and only spin. And I also drilled the hole after it was pressed so I never used any metal. I will need to predrill in the future so I can.
dagabu Posted July 28, 2016 Posted July 28, 2016 Nozzleless! Why didn't I think of that!?! Great idea, J! Thanks for that before I go off pressing a bunch tomorrow.
AzoMittle Posted July 28, 2016 Posted July 28, 2016 Does this look correct? I drew it at 1:1 scale. http://i.imgur.com/blwjCCe.jpg The forum is not letting post the picture directly to the thread, it says that the image extension is not allowed.
NeighborJ Posted July 29, 2016 Posted July 29, 2016 I have attempted to add a half hemi full of dragon eggs to one of these zippers but it ended in a Cato. I had made a spolette and pressed the header around it. Unfortunately in doing so the fuel grain cracked precisely where the spinner nozzle was located. I won't let this defeat me, I have plans to use green visco to passfire from the spinner nozzle to the 1/2 hemi.
dynomike1 Posted August 7, 2016 Posted August 7, 2016 Will 325 atomized aluminum work? I have that on hand.
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