braddsn Posted February 3, 2015 Posted February 3, 2015 Hey fellas. I want to have a certain strobing effect, but not sure how to get it. It's in the following video. The shell breaks at exactly 1:20, and a few seconds later, the pistil (or center) starts strobing green very quickly. Like a fast flickering effect. Does anyone know this comp or how to achieve this? I am guessing maybe an AP comp? It's awesome! Thanks!
Niladmirari Posted February 3, 2015 Posted February 3, 2015 Yes, it's AР base: АР / ВаSО4 / Mg / K2Cr2O7 / NC (acetone). I did yellow (Na2SO4). Fast flickering: 1
pyrojig Posted February 4, 2015 Posted February 4, 2015 (edited) Hardt has this comp, and even Blesser . It is a Ap comp indeed. I find that with a 200 mesh or finer mag or magnal, it is a common thing. Green is a fast stobe star, and it almost has that "shimmer " effect that I have been so longing for. Edited February 4, 2015 by pyrojig 1
Niladmirari Posted February 4, 2015 Posted February 4, 2015 Magnesium (Mg) is needed for fast flickering. I do not like MgAl for this composition. MgAl gives decrease in the frequency flickering. 1
braddsn Posted February 5, 2015 Author Posted February 5, 2015 That helps Niladmirari. I like the fast flickering instead of slow strobing. Looks very cool. It looks like you have mastered it. Well done! I am going to give it a try very soon.
pyrojig Posted February 5, 2015 Posted February 5, 2015 Some comps in Hardt's book ( on osculating stars/ strobes) shows that even faster "shimmering " effects can be obtained with the white stars( AP ) . With the addition of anhydrous Mag. sulfate. The comp must be bound in a phenolic / alc or other " water proofing" binder. Mag sulfate loves water. I still have to try this comp myself. but have enjoyed the green AP strobe with Mag, from Hardt's book, and the one from David Blesser as well. Very fast flicker.One thing to address , strobe comps appear to burn faster on the ground v.s. the air. The movement through the air slows the burn rate a lot. I also find that proper priming is essential to good performance AP strobes. I have had past experiences with low ignition rates if not step-primed.
enanthate Posted February 5, 2015 Posted February 5, 2015 How about the red nitrate strobes discussed in a different thread, can they be made to strobe as quickly as in the video?Its based on pot chlorate, str nitrate, mgal etc.I've tried it with 100mesh mgal, and 2% CuO to speed up, but on the sky its still very slow.I guess what im asking is does it have to be AP strobes?
Mumbles Posted February 5, 2015 Posted February 5, 2015 Pyrojig, there are also some white strobes based on barium sulfate. If you look at them carefully, they're not really pure white, tending toward a green or yellowish hue. If you look at Shimizu's formulas basically the green strobe uses Mg, while the white strobe uses MgAl. Otherwise they're almost identical. One trick that was passed along to me was to use a small proportion of strontium sulfate in the star to cancel out the color from the barium. I've never done it, but allegedly only a few percent is needed to do the trick. It works for rockets at least. Then you don't need to screw around with drying MgSO4, and super waterproof binders. Nildiamari, for what it's worth Shimizu's data greatly disagrees with you. The green and white strobes I just mentioned have flashing frequencies associated with them. I don't have my actual book to cross-check, but the MgAl (white) strobe is reported to have a rate 3x faster than Mg. I don't understand it. You can also just change the particle size of the metal to increase the strobe rate. I'd start with the formula as written, and start changing out say 100mesh metal for 200 mesh metal slowly until you get what you want. Going too far can result in a star that appears to burn consistently or never fully have an "off" phase.
pyrokid Posted February 6, 2015 Posted February 6, 2015 Where is everyone sourcing their magnalium and magnesium for these strobes? Is there a favorite priming composition?
Niladmirari Posted February 7, 2015 Posted February 7, 2015 (edited) I used Mg 200-220 mesh. Edited February 7, 2015 by Niladmirari
rogeryermaw Posted February 7, 2015 Posted February 7, 2015 (edited) i tried the Shimizu green strobe with 200 mesh mg, 120 mesh mg, 80-200 mgal and 200-325 mgal. the 200 mg burned constant, the 120 mg strobed, but so fast it could only be heard, not seen. with the 80-200 mgal, the frequency was around .5-1 Hz. with the 200-325 mgal, produced the effect in my strobe test. http://www.amateurpyro.com/forums/topic/10192-rogers-pyrotechnic-offerings-and-experiments/?p=139859 the magnesium strobes appear to show more green while the mgal appear more white. Edited February 7, 2015 by rogeryermaw
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