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Does the ID of a tube and length help determine the height a star will reach?

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#1 AndyPyroNoob


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Posted 31 December 2021 - 05:11 AM

I have a 4 inch tube, ID of approx 3/4 inch. I have placed a star which is slightly under the 3/4 inch size.

I put approx 2 grams of Lift powder in the tube and the star gets some height but then lands on the ground still burning.

I can then place 4 grams of lift powder in the tube, same size star and it still hits the ground and is still burning,


1/2 inch stars don't have this problem, obviously the 1/2 inch stars are not burning for as long. They don't need as much height.


As an example you can purchase a star gun like this one here https://www.woodysro...Star_Gun.html#/


Is the ID of a tube directly related to the length of the tube for the star to get enough height?


I do not believe its my lift as on the ground when it ignites it goes up very fast and no residue. I have Home Made Pine charcoal in my BP. Should I be using Horticultural Charcoal instead for my Lift?


I think I am going to try the attached image ID tube and length, star weight and Lift powder weight to see what happens( Maybe not 300 of them though :P), unless someone can suggest to me an alternative to get my bigger stars in the air higher?

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#2 SeaMonkey



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Posted 31 December 2021 - 11:19 AM

It may be that your 4 inch tube is too short to develop sufficient velocity for your star to attain the height you want.


I'd be using a 12 inch to 18 inch tube if I were doing the testing.


Charcoal is the most important part of your BP and Pine Charcoal is one of the best.  Home made charcoal is much better than horticultural charcoal for BP.


Keep at it, you'll soon discover what the problem is.

#3 Carbon796



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Posted 31 December 2021 - 11:40 AM

A minimum ideal length is 7 x the ID.

Star type also plays a roll. Color stars typically burn longer than charcoal based ones, for a given size.

If your shooting charcoal based stars. And they are hanging on to any water. This can slow them down some. Even if they appear to be dry.

Your BP is also probably somewhat slow. Pine is great for sparks. But woods like paulownia,red cedar, balsa, adler, and willow. Will easily out perform it.
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#4 MadMat



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Posted 31 December 2021 - 03:29 PM

I agree with the answers given. Just one other thing I would like to mention; with a short tube, adding more lift powder won't help. You will get to a point where the star has already left the tube before all the lift has completed burning. Get a longer tube! Are your stars cut (square), pumped (cylindrical), or rolled (balls)? You can wrap a bit of paper around the star, creating sort of a sabot. This will make a tighter fit. Just make sure the bottom of the star is uncovered and able to take fire from the lift charge.  A tighter fit, gives better containment, which makes for better lift power with the same amount of powder. If all things are optimized, a larger star should travel higher. A heavier projectile (within reason) will gain more inertia from the lift charge, which will result in a higher flight. Don't think a heavier projectile will travel farther? Consider the 16" cannons that were mounted on battle ships during WWll. They could fire a 16" shell weighing in at a little over a ton over 27 miles! They did this with a "lift charge" of close to 900 lbs. of powder. I don't care how much powder you put behind a 5.56mm bullet, you will never get it to travel anywhere near that far. It's all about the inertia of the projectile

Edited by MadMat, 31 December 2021 - 03:53 PM.

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#5 Arthur



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Posted 31 December 2021 - 05:39 PM

The fit of star in tube is also important.  

#6 Mumbles



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Posted 20 January 2022 - 02:18 PM

Black powder is also pressure dependent.  The higher the pressure the faster it burns, and typically the better or more efficient the lift is.  Real fast black powder typically has no issues with self-pressurizing itself.  If it is a bit slower, I have had issues in the past.  My black powder in retrospect might have been a little less than optimal.  One amount might flop a shell out of the gun, but slightly more might fire it to the desired height.  Finer grains can help with this.  The other thing that may help is to ram a wad of paper or tissue or cardboard over the top of the star.  It sort of self-contains it and can help to get it over the hump to get up to higher pressures and fire the star higher. 

Just so you guys quit asking, here is the link to the old forum. http://www.xsorbit2....forum/index.cgi

The sky is my canvas, and I have 2,113 pounds of powdered paint in the workshop.

#7 Arthur



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Posted 22 January 2022 - 01:00 PM

IMO a 4" tube is short maybe too short especially as you have to lose some depth with the necessary end plug. Try to find a top plug that fits tightly in the tube to ensure that the powder develops it's full pressure and ejection force.

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