Strobe rockets

[llamazares]

It is necessary to use Potassium Dichromate in the formula strobe rocket?

 

60 Ammonium Perchlorate.

23,5 Al/Mg -200 mesh

15 Barium Sulphate

5 Potassium Dichromate

1,5 Magnesium dust

 

Really, what function does this substance (suspect carcinogen) incorporated into the strobe mix?

 

I have doubt in to manipulation with this substance... but I have seen videos and these rockets are magnificent flight: very high, emitting a typical noise!!!!!!

[optimus]

Potassium Dichromate is usually used to coat Magnesium powder, enabling it to be used in combination with Ammonium Perchlorate without causing the mixture to heat up and possibly catch fire, which could happen if you used uncoated Mg. It is also added in powder form to some formulas to inhibit this unwanted reaction.

 

So, I wouldn't try the formula you mentioned without using K2Cr2O7 - it could lead to a nasty accident.

 

A search should bring up more info, including the coating process.

[Mumbles]

It will also somewhat protect the MgAl. In addition to it's protective properties, it serrves as a catalyst in the decomposition of the perchlorate ion, allowing the composition to be lit easier.

[Frozentech]

I've been researching this same topic a bit lately. I've experienced the reaction between ammonium perchlorate and MgAl and it's scarier than dichromate to me, so I have treated 100 grams of 200 mesh MgAl, haven't gotten around to using it yet tho.

 

One thing I found was that there is a mixture that will negate any protection of the Mg in the MgAl with dichromate. Barium Nitrate green strobe comps with MgAl and Ammonium Perc, evidently the nitrate reacts with the Al in the MgAl, and wrecks the chromium coating on the Mg ? Sounds plausible, so I am still doing more research.

 

Hopefully pretty soon I will get around to trying it out, I have strobe rocket tooling that I hate to have just sitting around all virginal

[keepkool79]

If anyone has made the 4lb strobes please let me know how much whistle mix you used before the strobe mix. How much comp in each increment? I’ve got the 2lb strobe rocket working great but my 4lb strobes blow up.

Thanks

[llamazares]

I've been researching this same topic a bit lately.  I've experienced the reaction between ammonium perchlorate and MgAl and it's scarier than dichromate to me, so I have treated 100 grams of 200 mesh MgAl, haven't gotten around to using it yet tho.

 

One thing I found was that there is a mixture that will negate any protection of the Mg in the MgAl with dichromate.  Barium Nitrate green strobe comps with MgAl and Ammonium Perc, evidently the nitrate reacts with the Al in the MgAl, and wrecks the chromium coating on the Mg ?  Sounds plausible, so I am still doing more research.

 

Hopefully pretty soon I will get around to trying it out, I have strobe rocket tooling that I hate to have just sitting around all virginal

 

Frozentech:

 

Please, it transmit of your experiments on these metals with the participation (or not) of the potassium dichromate and also on his success or failure in yours Strobe Rockets...

I wait impatiently for your news !

[keepkool79]

Why are everyone’s pics so big?

 

Anyway, I have that diagram but thanks all the same. I am trying to find the best increment to use and that is not shown on the paper. By increment I mean how much comp to add each time you press. For example, when making 2lb strobe rockets using the universal spindle I add 10 grams each time I press.

Thanks,

[llamazares]

Every increase, once compact with the rammer, must occupy an inside diameter of tube.This it is the rule that appears in the news. I believe that the ideal thing is to be done a spoon calibrated in volume that correspondss to every press increment.

[Mumbles]

There is no need for pictures that big. Feel free to reattach the last two if you want to, and they are smaller.

[keepkool79]

The increment question may sound like a dumb one but I am really having a hard time with it. John Steinberg sent me an article he wrote for the PGI newsletter and in it he says that you are to use 3-1/2 tablespoon increments. When I tried my 4lb strobe I pressed them up and it blew. Now, some of you may say, o-well, just a little Cato, try again until you get it right. I want to say that these things sound like a fucking bomb went off. When I tested it I was in the middle of nowhere and as I was driving away I was passed by 2 fire trucks, 5 police cars all with lights on heading to that area. I did not hang out to find out why they where there but I think I know why. So, when I made it everything else seemed right and now I would just like a guideline to go by. I am thinking 1-1/2 or maybe 2 table spoons. I know someone on here has made these 4lb rockets so please let me know. I do not want a repeat of the last test.

Thanks,

[TheSidewinder]

Uhhh.... he didn't mean three, 1/2-tablespoon increments, did he? That would make more sense to me. I've read that increments should be NO MORE than a half-diameter in height, and a quarter-diameter (in large rockets, i.e above 1 lb) is better, though time-consuming.

 

But I don't specifically recall whether this was true only for BP rockets, or whether it was also true for strobes and hybrids. Steve LaDuke makes wicked strobe and hybrid rockets, and I'm fairly sure he uses the "less than half-diameter" measure.

 

I'd suggest a *maximum* of a half-diameter in heigth for an unpressed increment (and I don't think that's anywhere NEAR "3-1/2 tablespoons").

 

Also, are you SURE of your pressures? I seem to recall that whistles and strobes need much higher pressures than BP rockets.

(Someone correct me if I'm wrong here?)

 

M

[FrankRizzo]

The increment question may sound like a dumb one but I am really having a hard time with it. John Steinberg sent me an article he wrote for the PGI newsletter and in it he says that you are to use 3-1/2 tablespoon increments. When I tried my 4lb strobe I pressed them up and it blew. Now, some of you may say, o-well, just a little Cato, try again until you get it right. I want to say that these things sound like a fucking bomb went off. When I tested it I was in the middle of nowhere and as I was driving away I was passed by 2 fire trucks, 5 police cars all with lights on heading to that area. I did not hang out to find out why they where there but I think I know why. So, when I made it everything else seemed right and now I would just like a guideline to go by. I am thinking 1-1/2 or maybe 2 table spoons. I know someone on here has made these 4lb rockets so please let me know. I do not want a repeat of the last test.

Thanks,

Keepkool,

 

A 2 tbsp increment of 20-mesh riced powder, pressed to 8000 psi loading pressure is what I use. Each increment gives ~1/2" of pressed powder height.

 

Steinberg presses both his 2lb and 4lb strobes at 6152.6 pounds of force, which equals over 10000 psi loading pressure for 2lb rkts and a little over 5000 psi loading pressure for his 4lb'ers. You may have noticed that the whistle mix he uses for the 4lb rockets has an extra 1.5% vaseline and is a bit heaver on the salicylate...likely to slow the mix down so they don't CATO with such low loading pressure.

[Mumbles]

Another thing to consider is your press. I have heard that some lower quality presses tend to give a tad, which will lower the pressure. A good stiff press should be used on things like this. I may be a little worried about using a hobby fireworks press on a 4lb'er. They just don't look extremly sturdy to me, but I have never seen one in person.

[Tweetybird88]

Is a strobe rocket a single composition that provdes the thrust as well as the effect or is it layers of compositions, one to create thrust and one to create the effect?

[Mumbles]

Two layers. The thrust part on the way up is whistle. The strobe portion is the delay portion if you will. When pressing BP rockets often people will use the solid portion above the spindle as a delay portion with Ti or other things like that that would scratch the spindle. Strobe rockets use strobe instead of glitters or fireflies or what not. Strobe burns pretty slow, so 1/4" to 3/8" only is used. Then an additional portion of whistle is usually then put on top of it to fill up space or get it moving again or whatever before the header goes off.

[psyco_1322]

I made some strobe w/o dichromate and it seems to burn uneffectivly slow, I did use 325 mesh magnalium though, my formula doesnt have Mg in it though. I believe its LaDukes formula.

 

How much will a 1# strobe lift?

[Mumbles]

The dichromate is a burn rate catalyst in addition to theoretically protecting the Mg portion of the MgAl. Using it will drastically improve the burn rate. As for lifting amount, you'd have to ask someone else. I'd say at least a 4" ball shells so 300g or so.

[psyco_1322]

Ya, thats my reasopning on why the first rocket didnt fly and the second burnt all the way to the ground, and the strobe granulals dont like to burn constantly.

 

and my strobe started bubbling after I added in the NC lacquer and began mixing, I added some boric acid and it helped to calm down the reaction, it didnt start heating up though. It eventually stopped. What is this reaction and why is it happening?

 

Oh and Mumbles have you checked you PM lately?

[FrankRizzo]

Actually Mumbles, the dichromate is detrimental to the strobe effect. I was speaking with Ken Miller who made strobe pots for a pyro company in ND years ago, and he said the less you use the better the strobe effect will be. Anything more than 1-2% will decrease the strobe rate because of the lowered AP decomp. temperature (less energy to impart to the sulfate/strobe part of the reaction).

 

@Psyco: The strobe comp that I helped Bill and Randy make at PGI used only 2% dichromate.

 

The bubbling was likely just entrapped air and nothing to worry about if there was no heat evolved. Once the NC is dissolved in the acetone, it doesn't have as much of a propensity to absorb water from the air as straight acetone would. Leave the boric acid out.

[Mumbles]

That is a good point about the strobes. I never really thought about it like that. Too much could indeed lower the Activation energy to an extent where it's not two distinct phases.

 

Though I'm not sure, activation energy is just energy needed to start the reaction. It has no impact on energy released. I've talked to Ken before too, he may just not know it. It never really came up though. To be fair, I'm not sure if it acts as a pure catalyst (lowered activation energy), or as a secondary oxidiser, which will actually release less energy. In a strobe comp it may be a tertiary oxidiser, but you get my point.

[invisibleworld]

You said that my MGAL that I have will work. That is what is called for in the AFN video and I also talked to John Steiburg, he also said I needed 200 mesh. What are you using?

For those that are using the MgAl strobe composition: Have any of you tried the composition below? I ask because MgAl is too expensive for me.

 

Ammonium perchlorate -63

Black copper oxide -10

GE Silicone II -22

PVC -5

 

There is no MgAl so it eliminates the problem of "what mesh should my MgAl be" and the only reason that I can think of using the composition used by FrankRizzo is that it'll give a brighter strobe.

 

So is there anybody that has tried this composition of something similar?

Yes I tried it. You can find the instructions at Skylighter.com. I have used it in a 1lb black powder tooling and drilled out the choke 5/16 inch and I used it on a 4 oz P/B tooling The 1 lber poped and sputtered and picked up speed to sound like a machine gun , lifted off and climed to about a hundred feet, made a 90 degree turn,and flew off horizontal for about 1000 feet. It looked so COOOOL and it sounded and flew just like one of those German V-1 buzz bombs, I made three more and left the nozzle the original size on the last two. the only difference was that it started out making louder bangs before it spead up and it rose to about 200 feet, but still turned and went horizontal, which I think is the best atribute. I made up a batch tonight, and loaded it into some 4 oz rockets, but I have to wait to drive out of the city to shoot them. PS the stuff is like gooey rubber. When you press it, it likes to do some type of hydrolic crap and split the tube even with a sleeve. The instructions say to press it while it is still wet, but this time I let it cure half way then screened it. It was a lot nicer to handle and it pressed better, Just got to go a little light on the PSI's because when it is a semi-liquid, it blows out the tube with what seems like only the slightest pressure.

[Mumbles]

Did you actually get any strobing out of that composition? I've never heard very good results from it, rather just a rather poor propellant that burns blue. Nice color, but no strobing.

[invisibleworld]

Yes it did, but it was more of a flashing as it sputtered. Not like a strobe pot, but more like a constant series of controled explosions and it is a pretty blue. I forgot to mention that after you press the stuff, if you do it while still wet instead of screening it when partialy cured, the leftovers make great stars. when burning, they shoot around like the flying fish fuse. They are a little hard to ignite, but if they are primed they are fine.

[psyco_1322]

Back @ Frank: No Ive had it happen before when making some wierd white strobe stars, turned out then burned green, they expanded and swelled up. Never had it happen with anyother star comp. Maybe the boric acid slowed it down, na not as bad as it is, shit cant even keep itself burning.

 

Mumbles ive made blue strobe before but never used it properly, in a rocket. This is a video of a rocket I made with 4oz bp tooling, just straight strobe with a nozzle. Dont think Ill do it again though, I just hand pressed it in(with a hammer) and it clogged all up into my tooling and took me awhile to clean.

 

http://i108.photobucket.com/albums/n3/psyc...22/S4020734.jpg

 

http://s108.photobucket.com/albums/n3/psyc...nt=S4020735.flv

 

invisibleworld what kind of tooling did you use for the 4oz? Not sure if thats a typo or Ive just never heard of P/B tooling.

[FrankRizzo]

Back @ Frank: No Ive had it happen before when making some wierd white strobe stars, turned out then burned green, they expanded and swelled up. Never had it happen with anyother star comp. Maybe the boric acid slowed it down, na not as bad as it is, shit cant even keep itself burning.

Yeah, barium sulfate strobe mixes don't really burn "white". To make them white, substitute half of the barium sulfate with strontium sulfate.

 

As for bad reactions (swelling, etc.), this shouldn't happen unless you've got some water in the comp or your magnalium is too fine.