Lift powder 4 inch shell

[gregh]

Mumbles, the discrepancies in terminal velocities are due to differing figures for the coefficient of drag. The 72mph is figured with the assumption of a perfectly smooth ball and a drag coefficient of .5. However, NASA has done extensive testing on baseballs in wind tunnels and found Cd to only be .3 due to the stitching. This gives the figure closer to 95 mph. The two takeaways from this are that sometimes physics seems counter-intuitive, with the stitching decreasing drag, and NASA wastes our tax dollars on some stupid shit! (Unless of course, you are a pyro looking for the terminal velocity of a baseball for your BP tests, then it's money well spent)

[Merlin]

I modified my calculation for 66% of total flight time and subtracted the horizontal distance to impact in feet. I think 500 feet is a reasonable result. Of Course the charge would be reduced for a 3 inch shell but probably almost right for a 4 inch with a bit more BP added for weight difference. I rather be high than low.

[Wiley]

I feel like 500 feet is going to be too much for a 4" unless your shells are breaking huge. Put 4 seconds of fuse on your shell and try 10% of the shell weight for lift. Sounds like your powder is plenty powerful; just let us know how it goes.

[RiderX]

hi guys im new here , and cant post a new thread apparently , ive tried making my own bp with skylighters red gum kit, and its lifting the shells but not high enough

im curious as to how much lft i should be using for 3" 100-150 gram wieght shells

 

last shell i tried was 122 grams finished wieght , and i used 32 grams of homeade bp lift with a 2.5 second time delay on the shell , the shell burst on its way back down

i do belive part of the issue is the shell was sloppy in the tube , but after pasting 7 layers by hand i figured it try it

 

i did do another identical shell this time after pasting the first few layers i wrapped a few turns of 1/2inch wide gummed tape around the seam of the shell and then pasted 2 more layers , this fits in the mortar tube much tighter i just havent had a chance to try it just yet to see how much of a difference between the 2

Edited July 18, 2017 by RiderX

[Merlin]

As stated earlier in this thread. Do not use hardwood airfloat charcoal for your lift or burst. For the shell you describe 20-25g should be more than adequate.

[RiderX]

As stated earlier in this thread. Do not use hardwood airfloat charcoal for your lift or burst. For the shell you describe 20-25g should be more than adequate.

so the charcoal that comes in the skylighter kits is no good then atleast for litt powder ? Anychance u could point me to where i can buy better charcoal.

 

what kind of fit should i be aiming for in the tubes? and how much difference will the fit in the tube make , the hemis im using are 2 5/8 outside actual diam. and im pasting with reinforced gum tape , the only thing i could get was 3 inch wide stuff , so i cut off the proper lenghts then cut them into 1/4 or 1/2 inch wide strips

 

the rolls of 1/2 wide non reinforced i bought is just way to thin

 

i still have a shell i pasted with only 7 layers , ill have to dig out my calipers and find out what it outside measurement actually came to

Edited July 18, 2017 by RiderX

[Merlin]

You want your shell to roll down the tube, you don't want to force it. i would say 1/8" all away around. You will just have to take notes and see how many layers it will take. Ball shells require a lot of pasting which is why I finally went with cylinder shells. much simpler

As for the charcoal there are places that sell. i just checked at fireworkscookbook and they have eastern red cedar and paulownia both are excellent.

Depending on where you live you may ultimately want to make your own charcoal. Most of us do. Very easy with a TLUD and ERC pet bedding from walmart. That's what i do.

The hardwood charcoal can be used to make BP. Just not so much for lift or burst. You can make polverone to fill spaces in your shell between the stars and hwd is good for making stars.

You may want to test your BP by firing baseballs and timing the flight. 25 grams gives me 11-12 seconds. just make sure they fall in a safe place- preferably not one's head!

Edited July 18, 2017 by Merlin

[RiderX]

You want your shell to roll down the tube, you don't want to force it. i would say 1/8" all away around. You will just have to take notes and see how many layers it will take. Ball shells require a lot of pasting which is why I finally went with cylinder shells. much simpler

As for the charcoal there are places that sell. i just checked at fireworkscookbook and they have eastern red cedar and paulownia both are excellent.

Depending on where you live you may ultimately want to make your own charcoal. Most of us do. Very easy with a TLUD and ERC pet bedding from walmart. That's what i do.

The hardwood charcoal can be used to make BP. Just not so much for lift or burst. You can make polverone to fill spaces in your shell between the stars and hwd is good for making stars.

You may want to test your BP by firing baseballs and timing the flight. 25 grams gives me 11-12 seconds. just make sure they fall in a safe place- preferably not one's head!

thank you very much , firing baseballs wont be an issue i have a few hundred acres with absolutely nothing around except my own head lol, i just did a shell with like around 1/16th clearance in the tube ill see if that helps any which if it does will atleast keep me going for now until i can get some better charcoal. if i had to guess id say i had more then an 1/8th on the ones i tried so far

 

ball mill is actually next on my list so i dont have to make the denatured alcohol and red gum bp

 

right now im just doing zinc cut starts and the d1 glitter once i get the hang of it ill move onto other stars , then after that i would really like to move onto crossets and torbillion inserts which i really really like

 

thanks again im sure there will be many questions form me in the future

Edited July 19, 2017 by RiderX

[Merlin]

Your welcome. lots of more knowledgeable people on this forum than me. Read everything you can on this site and pass fire and fire working. Study about good ball mills. I bought two before I got the one i use now. Read about TLUD

If i can make one anybody can. Read read read and ask questions.

[RiderX]

heres a video of the one shell i did , was the very first batch of d1 i made , which actually wasnt dry enough yet when i shot this i figured after 1.5 days it would have been completly dry , i just threw 3 inserts inside the shell and used some of the bp for burst actually glad i didn't fill it with stars

 

 

deffinatly not making it up high enough

Edited July 19, 2017 by RiderX

[Baldor]

I think the ball mill needs to be your first priority now, before you start experimenting with different charcoals. Try to get the most from the charcoal you have now (and the ball mill will make a lot faster BP), find a good granulating process, and then you will be at a point where you can compare. Change only one variable at a time, and you will know what works and what not. Of course, the experience of other forum members will expedite the process pointing you in the right direction.

[rogeryermaw]

heres a video of the one shell i did , was the very first batch of d1 i made , which actually wasnt dry enough yet when i shot this i figured after 1.5 days it would have been completly dry , i just threw 3 inserts inside the shell and used some of the bp for burst actually glad i didn't fill it with stars

 

deffinatly not making it up high enough

 

most charcoal stars take a few to several days to dry completely. in some cases you can speed it along with a drying box but you should allow them to dry naturally for the first couple of days to prevent "driven in" stars. this occurs when the outside of a star dries and forms a shell that won't let internal moisture evaporate away. the inside of the star will not dry under this condition. drying naturally in moderate to high humidity environments can take up to two weeks with large stars. more for big comets.

[RiderX]

 

most charcoal stars take a few to several days to dry completely. in some cases you can speed it along with a drying box but you should allow them to dry naturally for the first couple of days to prevent "driven in" stars. this occurs when the outside of a star dries and forms a shell that won't let internal moisture evaporate away. the inside of the star will not dry under this condition. drying naturally in moderate to high humidity environments can take up to two weeks with large stars. more for big comets.

thanks for the info , i live in utah so humidity in my area is usually around 3-8% , this last week its been up around 65% due to the rain storms in the area been miserable the last few days

 

i tested out another shell this morning with a new batch of bp , the shell finished diam was 2.768 inches , the shell weighed 163 grams and i used 32 grams of lift , the shell made it it to just about the right height (it went off while still rising with a 2.5 second time fuse ) and was launched at about a 80-85* angle over the wet field , so i think i may have a handle on the bp now , i wish i would have waited till tonight when it was dark but supposed to get a really good rain storm tonight.

 

if the rain holds off ill try another d1 shell tonight and video it , im going to aim for a 2.800 - 2.850 finished size on the shells from now on

[Mumbles]

One ball park rule of thumb is that you want the circumference of the finished shell to be about 3x the nominal diameter. For a 3" shell, this would be 9" around, or 2.86" in diameter. This corresponds to approximately 5% clearance. This isn't hard and fast, and I think your goals are right in line.

 

I will say that I've had the most trouble with 3" shells out of anything. There seems to be a lot more variability in the hemi size that other calibers.

 

Long term you'll probably want to move away from reinforced gummed tape. It's readily available and thicker, but generally too strong for our uses. Some people have gotten it to work though.

 

Putting the lift into a lift cup or otherwise providing a little reinforcement or containment can help with slightly undersized shells. Better confinement of the lift either by a good fit in the gun or lift containment will help to give better and more consistent results.

[RiderX]

One ball park rule of thumb is that you want the circumference of the finished shell to be about 3x the nominal diameter. For a 3" shell, this would be 9" around, or 2.86" in diameter. This corresponds to approximately 5% clearance. This isn't hard and fast, and I think your goals are right in line.

 

I will say that I've had the most trouble with 3" shells out of anything. There seems to be a lot more variability in the hemi size that other calibers.

 

Long term you'll probably want to move away from reinforced gummed tape. It's readily available and thicker, but generally too strong for our uses. Some people have gotten it to work though.

 

Putting the lift into a lift cup or otherwise providing a little reinforcement or containment can help with slightly undersized shells. Better confinement of the lift either by a good fit in the gun or lift containment will help to give better and more consistent results.

thank you , when i runout of hemi's im going to look for a slightly larger unfinished size.Im also going to look into building a pasting machine though generall not a big deal as i paste the shells after work when im rleaxing watching a movie or tv . but it would be nice to be able to to more , i generally am able to paste 1 shell a day after work

 

or maybe ill just switch to cyl shells , it shouldnt take me to long to run out i have about 50 sets of 2.5 hemis left and about 35-40 sets left of 3 inch