Lift powder testing

[Jordan]

I'm pretty new to the manufacturing of shells (although not the chemistry) and was wondering if it would be a good idea to test out lift powders at 1/10 weight on a non explosive shell I.e. baseball, softball. I have seen a fair number of shells have low or on ground detonations and would not like to see that happen in/ in front of a crowd.

 

Thanks All, Jordan

[bob]

Yes, testing ones lift powder with a dummy shell is highly requemended, also using a camera is very handy for getting accurate flight times.

This is where large batches of bp come in handy, because with every new batch you will have to retest and redial in your lift charges.

bob

Edited May 9, 2014 by bob

[LambentPyro]

Baseball testing and spollette testing are my top two BP testing methods. I'm sure there are others out there, but I find these to be the most accurate in my experience.

 

10% of the shell's weight is a good place to start. For 3" (baseball), if the flight time is about 9 seconds, you got it to a decent height around 300 feet or so.

 

Just watch where the baseball goes, it's a good practice to wear a hard hat and don't do it near any property or cars, that could be detrimental. If you don't think you'll be able to see it, I like to attach a slow burning and bright star to it and launch it on a cloudy day to make it easier to see.

 

Best

[jessoman]

I make a can shell filled with sand that I break (small) to test height and timings. So I'm not chasing balls . I live on the water too so I'm just giving the sand back to the ocean. It's handy stuff for pyro. Burying guns, sealing retort, baseball tests.

I've just been testing different woods I have easy access to recently so I've been doing a bit of these back-to-basics tests, just for fun!

 

Please test your lift with a dummy, low breaks aren't funny!

Test your timings too. Nothing worse than watching a shell reach it's apogee and it starts coming down and your think ING comeeee on!

Then double test. And again for consistency,

Edited May 9, 2014 by jessoman

[Merlin]

I am totally new to aerial shells. I wanted to start small(which may be mistake). I got a (kit) of 1" plastic spherical shells. All that was contained were bases ,tubes, the hemi-spheres, flying fish and visco fuse and what looked like paper end caps for salutes. My plans were to coat rice shells with milled bp for lift and burst. Not much room in those tiny hemis. Question one. Would bp rice hulls work? question 2. I can only suppose the paper cups hold the lift charge and would be taped to the bottom of the hemis with visco running to a punched hole in the paper cup and into the bottom of the shell. I can see no provision for time fuse, quick match or any or type fusing I have read about. Looks to me like if the rice hulls worked for lift the visco would simply ignite it and a split second later ignite the burst. Any comment or direction to instruction would be appreciated. The company I bought this from has not responded at all- probably too busy for such elementary questions. Thanks

[Jordan]

Using mcrh (meal coated rice hulls) on such a small shell usually doesn't work. Try to use 2FA grade granulated black powder for burst.

The only reason mcrh is used is to reduce weight. If you had a 12 inch shell and you used granulated BP It would take 20lbs. Of 2FA. If you put the BP on rice hulls it would reduce the weight because the rice hulls are acting as a carrier for your burst. MCRH is also not a very good lift "powder" try to use 2FA or 4FA for lift. You might have to experiment with powders for lift and burst. A good rule of thumb for lift is 10% of the shells weight. Although I'd put a little more since your shells are so small, maybe 12-16%.

 

Yours in Flames, Jordan

[Mumbles]

Where did you get this kit from? Your descriptions are good, but pictures are worth a thousand words. For what it's worth, I find working with larger shells easier to start from. I'd normally recommend about 3" or so. 3" and up is made with basically the same methods. Below 3", you generally don't gain the same experience or the same feel. Most things under 3" are generally little more than splashes of color or tails.

 

I think you mostly have it. One half of the plastic hemispheres probably has a hole about 1/8" wide in it. This is to accept visco as a delay fuse. They may also be designed to be side fused. A hole will be drilled slightly above the plug to accept some visco allowing you to retreat before it lifts.

 

The one thing I'm unsure about it are the paper plugs. You only need a lift cup if you're using quickmatch or another form of top fusing. They might be intended to press in afterwards to sort of seal everything in. This also helps to use the lift more efficiently.

 

Given the size you're working on, I'd recommend 4FA or finer (or the homemade equivalent) for both lift and burst.

[TYRONEEZEKIEL]

For my 3" ball shells, I always used 10% lift which worked alright in my case. One thing I've noticed that makes such a big difference is shell clearance in the mortar. Its surprising what +-1/8" clearance does to shell heights. Make sure you really get the shell thick enough to catch all the lift gases,(but still able to come out of course.)

[Arthur]

Sending a hard ball into the air means that you need lots of space for it to land. Sending a sand loaded shell with a break charge means that the debris is smaller and less likely to damage anything when it lands. Alternatively over lift your test shell, then you can reduce the lift next time. The nice bit of timing fine tuning is to suit the lift and the spollette so that the apogee is at the right height and that's where the break happens.

 

IMO a 3" shell is a good start for beginners as there is room inside for stars and a simple burst system but the amount of content and lift isn't very great. Bigger shells cost a lot because the content increases dramatically with diameter, with smaller shells it's hard to do the paper work neatly first time and the break may well need a lot of flash booster which immediately necessitates more ingredients and more manufacturing skill.

[TYRONEEZEKIEL]

3" shells are THE perfect size to learn shell building with. The cost of 3's are so low and still offer many of the techniques and skills to full scale shell building. I test baseballs all the time with my powder. I love the sand idea, I may start doing that too.

[Merlin]

I want to thank everyone for the advice. I am new and I am a retired chemist so it's not the chemistry. Obviously this tiny little shell presents its own problems besides being too small to work with.

I am very cautious about shells because there must be a explosion to lift them and then it is so critical they not burst too soon or too late. I should have known from my model planes- the larger ones are easier to build and fly. Lift testing with sand makes a lot of sense. The company I got these from didnt have anything else smaller than 2.5 to 3 inch in stock but to their credit they did respond and said they will print up detailed instructions. Credit to pyro-direct.

Thanks to all. Great forum.

[FlaMtnBkr]

I have used a baseball to test powder. I paint them neon orange to see them easier. But other than noting gets to an acceptable height it is hard to judge the quality of your powder.

 

There is a BP tester that was developed by members of the FPAG guild. I wish more people would use it and post results. It uses a PVC 'shuttle' that is made a certain way and is adjusted to a certain weight. It slides over a copper tube 'launcher' and then 4 grams of powder added. A series of tests are performed and the flight times recorded and averaged. Goex is supposed to provide a 5 second flight time and is a good base line. If your powder produces longer flight times than you know it's a bit better than commercial Goex. Once I made mine I started making charcoal from any source I could easily source. Then made BP using the same procedure and milling times. Just about all my homemade charcoal did better than the Goex with a few exceptions. One bush/tree species that I have yet to identify made 9 second BP. Getting close to double the Goex time and with the same 4 g sample. I believe a copy of the article is on Skylighter.

 

I need to make a new shuttle because I lost it in the trees last time I used it. I would like to try some Balsa and other hot charcoals and see how they compare. If I remember right, black willow was around 7-7.5 second powder. But if others made and used the tester, we could get a good idea how our BP compares to other's and also what different types of charcoal do on average. Would be neat to see who could get the longest flight time. I'm still impressed with the 9 sec stuff as it was about a second longer than any of the other dozen or so charcoal I made.

 

Also, with a visco time fuse, you probably need to wrap it so it doesn't side spit and light the shell too early and also lights the center of the shell. I have not used visco myself but always thought the real aluminum duct tape would work good.

 

I would use granulated BP and not coated rice hulls in such a small shell. Also, many small shells get a pretty good performance enhancement by using a booster. Something like flash. However, flash should be one of the last things you experiment with after you get your processes down and can handle such a powerful mix safely (or as safe as possible at least). I'm still a big fan of TPA 'safer' flash. Unconfined it burns slower than many star comps.

[nater]

FlaMtnBkr - Can you think of any reason I shouldn't share a link with the design for the shuttle tester?

[Mumbles]

Given that it's available on skylighter publicly, I see no reason not to share it. http://skylighterpromos.s3.amazonaws.com/Polverone.pdf

 

Make sure to test in an open area. I believe someone got one of these through their windshield once.

[nater]

Thanks for that link. I didn't know it was posted on the Skylighter blog, the only copy I had seen before was on pyrobin.