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

[AndyPyroNoob]

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.woodysrocks.com/store/p129/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 ), unless someone can suggest to me an alternative to get my bigger stars in the air higher?

[SeaMonkey]

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.

[Carbon796]

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.

[MadMat]

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 December 31, 2021 by MadMat

[Arthur]

The fit of star in tube is also important.

[Mumbles]

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.

[Arthur]

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.

[deepakpyro]

4 inch of length is too short for a star size of 3/4th inch. I would say after the after the end plug and bp layer stars will have approx 3 1/4 length to gain inertia to attain height. With this length the stars will not attained stability and you can't expect the stars to fly straight like mine cakes. As Mumbles said, you can use punched wad between the bp and stars and then a wad to self contain the force. Think of a shot gun, lower barrel length - more spread and less distance projectile travels vs high barrel length - longer distance and stable spread Edited January 30, 2022 by deepakpyro

[MadMat]

One last thing I should have mentioned a long time ago; a great way to test your powder is doing "baseball tests". This is actually launching baseballs from a 3 " tube. Generally speaking, you use 10% of the weight of the baseball for your lift powder. Get a stop watch and time from the boom of the lift to the thud of the ball hitting the ground. I usually ran at least three trials, four or even five would be better. Then average out the times. If you can get times in the range of 6.5 to 8 seconds of flight, you are making GOOD quality BP. When I first started out I would run baseball tests of every batch of BP I made. I would then make the necessary adjustments. After time, however, I perfected my BP making process and there was very little difference in time from one batch of BP to another. I still do baseball tests from time to time, but more for the fun of it than any real testing purposes

Edited January 30, 2022 by MadMat

[Smokelvr]

look up the concept of Caliber, it's a measure of barrel length, by bore diameter, so a naval 50 caliber gun, is 50 times the bore diameter, though most big guns were in the 30-35 range

most fireworks mortars are 6-ish times diameter. That said, you gain velocity (which is different than lift height) for length until addition pressure (gas expansion) is less than the friction/drag of the barrel

Which is an interesting concept with fireworks tubes, a low pressure system that is by design not tight/sealed, so the effective length is limited by the bypass loss/over time

 

Gist is, if you reload or target shoot you get passingly familiar with the concept of internal ballistics, and learn things like, for .223/5.56 the loss of range/power from the designed length of 20" (M16) to civilian carbine (16") is passable, but the drop off at 14" (M4) just barely... but gains past 22" are minimal for the added weight/bulk of the rifle.

[SharkWhisperer]

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.woodysrocks.com/store/p129/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 ), unless someone can suggest to me an alternative to get my bigger stars in the air higher?

Your BP is weak. Most folks who make weak BP make unpredictably weak BP; some batches are super wimpy and some are just wimpy. If you need 2g to 4g to lift a 3/4" star, that should be an indication you have BP quality/speed/power problems right there. And if it happens to be a cardboard tube and 2g is not exploding your 3/4" x 4" mortar, that would reinforce the point. 4g not blowing a cardboard tube seals the deal. A non-metallic 3/4" charcoal star only weighs a few grams, maximum. To use an equivalent mass of lift charge, whether you're testing in a 4" or 6" mortar, is a ridiculously high quantity of BP. I typically blast 20g of 3/4" sized metallic charcoal stars (combination of pumped with smaller cut to fill the voids) from a 1" x 7" steel gun for testing (more fun than single stars, but you can do that too). Lift charge is typically 10% of hot willow, ERC, or paulownia BP, granulated to around -10/+20 mesh. And often an extra pinch just because. They easily reach 60 feet. Any more lift than that and I'd just be blowing stars apart.

 

I'd be more concerned with improving your BP before worrying about mortar dimensions right now. And as Carbon mentioned, damp charcoal stars can appear completely dry but not be and burn slowly (to the ground...fire hazard).

 

What are your BP components and formulation techniques? Charcoal is key, as others mentioned. Milling will speed up any powder, crummy charcoal mixes included, though it'll never reach what you get with good charcoal. For many, making a first batch of actually good BP is an epiphany--"oh my!". It's important. If your lift is slow, your burst will be slow and you'll end up using band-aids like benzolift and flash supplementation when it isn't necessary. If you're not milling, and I'm guessing you're not or you might have mentioned it (and would know that 4g to lift a 3/4" star is ridiculously huge amount of BP), then that might be one of your first considerations (alongside charcoal selection). Even a cheapo HF hobby mill can make a huge difference. Even the few folks here that screen mix BP do so using milled starting components. If you're using a BP kit from any of the vendors, you're really starting off at a bad place--commercial hardwood charcoal is great for charcoal stars but complete crap for BP--your BP with CHF coal will always be mediocre at best.

 

What star formulation are you using? And different charcoal stars have different oxidizer:fuel ratios; some like C6 burn pretty quick, tigertail and C8 slower. All of them burn like old people screw if they have residual moisture--slow and sloppy.

 

What's your mortar made out of? A disposable cardboard job with a glued-on plastic base from cannonfuse.com or something more substantial?

 

Making reliably hot BP is a cornerstone of fireworking and you'll have a lot more successes, much faster and with less frustration, once you master that skill.

 

You'll get it!

[Richtee]

 

Gist is, if you reload or target shoot you get passingly familiar with the concept of internal ballistics, and learn things like, for .223/5.56 the loss of range/power from the designed length of 20" (M16) to civilian carbine (16") is passable, but the drop off at 14" (M4) just barely... but gains past 22" are minimal for the added weight/bulk of the rifle.

As far as velocity is concerned. However not accuracy and comfortability. I really appreciate that 26” barrel when I go to the range and pop 50 rounds, both physically and mentally