Coarse magnalium

[Mustapyro]

What is the coarsest Magnalium I can use for strobe fuel? I have some -10+50 but I'm concerned about it sparking when it crushes against itself.

Edited January 12 by Mustapyro

[Zumber]

It seems -10+50 is too coarse for strobe.

100 mesh 150 mesh 200 mesh or combination of single ,two or three different mesh would be a choice depending on burn rate and frequency.

Mesh size is responsible for burn rate and frequency.

Too coarse and too fine distroys effect.

[greenlight]

I have 325 mesh magnalium powder which is obviously too fine for strobe fuel so I purchased some 200 mesh magnalium.

It is flake magnalium though.

Will this still be okay to use even with the increased surface area provided by the flake form?

 

[Zumber]

Test a smaller batch like 100 grams.

 

[greenlight]

I have made a small 100 gram batch and the 200 mesh flake I ordered looks pretty fine.  

The finished product does not look too promising with no noticeable intermittent strobing when burned in a pile.

I will make a small scale test pressed into a tube before manufacturing an entire rocket motor.

I also have some magnalium chunks that were homemade in a furnace.  Would I be able to crush these with a hammer and grind further with a glass mortar and pestle to achieve a mixture between 80 and 200 mesh if this fuel doesn't give the desired effect? Maybe keep whatever passes through an 80 mesh screen?

 

 

 

 

 

[Zumber]

Post your formula.

If 200 mesh is not giving satisfactory result then change mesh size.

150 mesh or 100 mesh or combination of 100 and 200 mesh together.

[greenlight]

I am using:

Ammonium perchlorate   60

Barium sulfate   15

Magnalium (200 mesh flake)   17

Magnalium (325 mesh)    8

Potassium drichromate    5

Petroleum jelly   3

Lacquer thinner as solvent 

 

[greenlight]

Just did a test burn of a pressed sample of the above composition and no strobing at all just a very bright flare effect tinged slightly green from the barium sulfate.

So the magnalium is definitely too fine and the 200 mesh flake does not produce strobe.

I have chunks of homemade magnalium, can I reduce these in size with a hammer and then mill carefully in short intervals in a coffee grinder to get a mixture of lower mesh magnalium for the next test.

[Mumbles]

One tip with white strobes is to include a small amount (1-2 parts out of 100) of strontium sulfate.  It tends to kill the green tinge these sorts of compositions sometimes have.

I've seen it mentioned, but have never worked with flake magnalium.  Is it still a 50:50 mixture of Mg and Al?  The material we typically work with (50:50) is pretty brittle. I've never really wrapped my head around how it's formed into a flake particle. I'd have always thought it would shatter or break down into irregular chunks/granules than truly flatten out to a flake.  

[cmjlab]

Mumbles - my homemade Mg/Al that I let cool in the crucible before processing (instead of dumping into water to create "popcorn mg/al), often breaks down into flat jagged flakes.  Perhaps this is what is being referred to?

[cmjlab]

On 7/21/2024 at 11:06 AM, greenlight said:

"...I have chunks of homemade magnalium, can I reduce these in size with a hammer and then mill carefully in short intervals in a coffee grinder to get a mixture of lower mesh magnalium for the next test...."

I wasn't going to post this because milling Mg/Al is dangerous and often discouraged on here.  However I am of the opinion that it's better to warn people if why it's dangerous so that if they decide to do it anyways, they maybe don't hurt themselves (or worse).  So here goes........

****@Mumbles - please remove if this is inappropriate, and I won't post about it again ****

Here is the post I deleted earlier:

The homemade mg/al I've made by allowing it to cool in the crucible and producing  a solid chunk, can be broken down into smaller chunks with a hammer and a rag to cover it. 

I don't think it's a great idea to mill the mg/al unless you have fully researched all the risks associated with it, have the space large or remote enough that nobody gets hurt if your mill did explode, and you are willing to accept the risk of serious injury or worse if things go wrong.

If you decide youre going to do it anyways, ill list the 2 bihgest risks ive encountered - 

    1  - the milling media can get coated in the mg/al and cause sparks when you are emptying your ball mill jar as you pour them out.  I do not know the exact reason for this, but I was using Stai less stell media and saw sparks on almost every piece of media as it tumbled out of the mill jar in the evening and dang near needed a change of undergarments because it scared me so bad.  *Make darn sure you empty slowly and wear as much protective clothes / gear as possible.*   

     2 - you need to vent your jar frequently so that as the mg/al is reduced in size and becomes more reactive to oxygen, it has the chance to do so slowly.  It's reported to become pyrophoric and can ignite upon exposure to oxygen when you open the jar, if you do NOT vent it frequently while milling it down.  

There is also other information floating around in here about issues with milling your own mg/al.  I'd strongly encourage you to do lots of reading and ask questions if you're not sure on something.  Again, the risk is entirely yours.

Charles

Edited August 23 by cmjlab

[greenlight]

15 hours ago, Mumbles said:

One tip with white strobes is to include a small amount (1-2 parts out of 100) of strontium sulfate.  It tends to kill the green tinge these sorts of compositions sometimes have.

I've seen it mentioned, but have never worked with flake magnalium.  Is it still a 50:50 mixture of Mg and Al?  The material we typically work with (50:50) is pretty brittle. I've never really wrapped my head around how it's formed into a flake particle. I'd have always thought it would shatter or break down into irregular chunks/granules than truly flatten out to a flake.  

I believe it is a 50:50 mix and it was labelled as 200 mesh on the website.  But it is extremely fine and seems more like 325 mesh really.  I have not heard of flake form of magnalium until I purchased this.  

Upon pressing a test rocket with only strobe and a core with the composition with the flake mgal, it results in a loud brrrrrrrrrrp sound like an A10 thunderbolt instead of any real strobing.  I theorize this is die to tlvery fast oscillating in the burn duebto the higher reactivity and burn rate with the flaked metal.  It is strobing insanely fast.  It is definitely too fine and reactive for strobes in this flake form or it is incorrect mesh size.

Since then, I broke up the magnalium I made in a furnace with a hammer and gave it very short bursts in small portion in a coffee grinder to get a variety of sizes about 100 mesh to 200.  I made another batch and pressed a cored motor for a static test identical to the first.  This time I have proper "helicopter" like strobing although it's not as loud as I would like it to be its a massive improvement.

Edited August 24 by greenlight

[greenlight]

8 hours ago, cmjlab said:

I wasn't going to post this because milling Mg/Al is dangerous and often discouraged on here.  However I am of the opinion that it's better to warn people if why it's dangerous so that if they decide to do it anyways, they maybe don't hurt themselves (or worse).  So here goes........

****@Mumbles - please remove if this is inappropriate, and I won't post about it again ****

Here is the post I deleted earlier:

The homemade mg/al I've made by allowing it to cool in the crucible and producing  a solid chunk, can be broken down into smaller chunks with a hammer and a rag to cover it. 

I don't think it's a great idea to mill the mg/al unless you have fully researched all the risks associated with it, have the space large or remote enough that nobody gets hurt if your mill did explode, and you are willing to accept the risk of serious injury or worse if things go wrong.

If you decide youre going to do it anyways, ill list the 2 bihgest risks ive encountered - 

    1  - the milling media can get coated in the mg/al and cause sparks when you are emptying your ball mill jar as you pour them out.  I do not know the exact reason for this, but I was using Stai less stell media and saw sparks on almost every piece of media as it tumbled out of the mill jar in the evening and dang near needed a change of undergarments because it scared me so bad.  *Make darn sure you empty slowly and wear as much protective clothes / gear as possible.*   

     2 - you need to vent your jar frequently so that as the mg/al is reduced in size and becomes more reactive to oxygen, it has the chance to do so slowly.  It's reported to become pyrophoric and can ignite upon exposure to oxygen when you open the jar, if you do NOT vent it frequently while milling it down.  

There is also other information floating around in here about issues with milling your own mg/al.  I'd strongly encourage you to do lots of reading and ask questions if you're not sure on something.  Again, the risk is entirely yours.

Charles

Thankyou for the warning but I have never milled magnalium in a ball mill and am aware of the dangers of autoignition upon opening the mill from the rapid oxidation.  

Because i am only making small batches of strobe to test what I opted to do instead was place small increments (~2 grams) in a coffee grinder and grind for 10 second intervals and then opening between each one.  About 3 to 4 intervals resulted in a decent variety of sizes.  The grinder does expose anywhere near as much new reactive surface in 10 seconds as ball milling for an extended period does.

 

Edited August 24 by greenlight

[cmjlab]

I'm glad you figured out a way to break down your mg/al.  

I wish I could give you some tips for improving sound - I don't have any.  I've struggled to get working batches myself, and can't seem to nail down a common denominator between bad batches that differed from the good batches, that I could then point to and say "ah ha" that's the problem! 

It seems to me that when the stars align, and I offer my first born, I get decent strobe rockets! So I mainly stick to cylinder shells, since I only have 1 first born to offer.  🙂

[greenlight]

I know what you mean I thought ibwas halfway there when the natch of whistle sounded great but nope.

I have read that the strobe composition is that picky about performance that it can even come down to different batches of the other reagents like the barium sulfate source.

I think the primary cause of the sound and speed of oscillation is the MgAl particle size and ratio.  I have seen some impressive sounding strobes with magnalium mesh all the way up to 80.  Mixtures of 80mesh through to 200 and then 325 mesh in differing ratios seem to have good results from youtube. 

Another factor seems to be the pressure on the comp, maybe too much results in inadequate performance as well as too little.  

I think the particle size of the ammonium perchlorate has an effect too as well as the percentage of dichromate.

It seems a never ending list which diminishes your chances with each addition to it haha.