Muslickz Posted September 29, 2020 Share Posted September 29, 2020 So though I'm not new to pyrotechnics I am new to 3" and larger cylinder shells. I just completed building my first and it seems heavy? Is there an average weight I should be looking to hit?Its got a few dozen 1/2" Pumped stars and a 1" center filled with burst (BP with a gram or two of flash to help) Its weighing in at 395G? Also.. I'm seeing recommended amounts of lift at 20-30G for 3".. But what would you think would be a good amount for roughly 400G? I know it is dependent on quality of lift bp.. but just a general number.. my lift is decent and pretty standard. 400Grams just seems heavy? Here's a pic.. I made it with 40g of lift but I WILL be launching a dummy at 400g first to test. I will adjust the lift amount dependent of how the dummy shells goes. I basically just would like the input of a few Pro's. Thanks for the Input in advance... -Mus Link to comment Share on other sites More sharing options...
Carbon796 Posted September 29, 2020 Share Posted September 29, 2020 (edited) It probably seems heavy, because its over square. Thats almost the length of a 2 break 3". Or a break and report. For cylinders under 10 lbs. The rule, is an ounce of BP per pound. Though a single 3" usually just lifts at an ounce of BP. 40g should be fine for that. Theres no specific weight, you should be looking to " hit ". With cylinders you just build them, and they weigh what they weigh. Especially with multi breaks. Just an fyi, I'd cut the excess paper, on the bottom gather off, closer to the tie point. So the shell will sit lower in the gun. Edited September 29, 2020 by Carbon796 Link to comment Share on other sites More sharing options...
Muslickz Posted September 29, 2020 Author Share Posted September 29, 2020 Ok, so I did a test fire on a 400gram dummy shell. Just to be safe I used 50G of lift. Total time from launch to land was 9 seconds. Four Seconds to apogee and Five seconds on the on the return trip. Boy does 400grams of litter come down with a thud. I'm thinking 40-45G of lift would do it.. 50 seemed a Little violent.. Considering I have a Three second time fuse 45g should get me to apogee right around 3-3.5 secs. Does that sound right? Is there a simple way to find altitude based on seconds to apogee? -Mus. Link to comment Share on other sites More sharing options...
kingkama Posted September 30, 2020 Share Posted September 30, 2020 For my BP 15% of shell weight do the work. Link to comment Share on other sites More sharing options...
Arthur Posted September 30, 2020 Share Posted September 30, 2020 Is there a simple way to find altitude based on seconds to apogee? -Mus. Google "Equations of motion"You know that g is constant you know it's value in imperial and/or metric (32ft per sec2 or 9.8 m/sec2 )You know the rise time and that the velocity at apogee is zero Well that ignores air resistance. Link to comment Share on other sites More sharing options...
a_bab Posted September 30, 2020 Share Posted September 30, 2020 (edited) Made many years ago a similar shell and 40g of BP sent it to the moon; it was way too high to enjoy the break and was still going upwards when it broke.You should remember the cyl shells offer more confinement than the spherical ones due to the flatness, so the mortar needs to be stronger (not a problem with small calibers but the larger ones would need really heavy tubes, some use steel). Edited September 30, 2020 by a_bab Link to comment Share on other sites More sharing options...
Carbon796 Posted October 1, 2020 Share Posted October 1, 2020 You don't really need to worry about reinforced or steel guns. Until your on the north side of 10 lbs. Most commercial quality fiberglass mortars are fine till then. Link to comment Share on other sites More sharing options...
Muslickz Posted October 1, 2020 Author Share Posted October 1, 2020 Is there a simple way to find altitude based on seconds to apogee? -Mus. Google "Equations of motion"You know that g is constant you know it's value in imperial and/or metric (32ft per sec2 or 9.8 m/sec2 )You know the rise time and that the velocity at apogee is zero Well that ignores air resistance.Ty Sir! I'm on it.. But yea I was trying to consider Air resistance.. lol.. over complicated it I think.. You don't really need to worry about reinforced or steel guns. Until your on the north side of 10 lbs. Most commercial quality fiberglass mortars are fine till then. I'm currently using a 1/4" thick fiberglass 18" Tube? It seems to handle what I'm throwing at it so far.. I also half bury it... Made many years ago a similar shell and 40g of BP sent it to the moon; it was way too high to enjoy the break and was still going upwards when it broke. You should remember the cyl shells offer more confinement than the spherical ones due to the flatness, so the mortar needs to be stronger (not a problem with small calibers but the larger ones would need really heavy tubes, some use steel).I saw that, 50g seemed to throw the dummy shell what looked to me like 500 or so feet.. wayyyy up there.. You guys rock, thanks for all the advice!I'll try and get a vid or two up of my progress! -Mus Link to comment Share on other sites More sharing options...
Arthur Posted October 1, 2020 Share Posted October 1, 2020 If only there was a simple way to determine flight characteristics without knowing all about the shape and surface of the projectile. Link to comment Share on other sites More sharing options...
BetICouldMake1 Posted October 1, 2020 Share Posted October 1, 2020 Per the strong mortar comment keep in mind that a 10lb 4" will create significantly higher pressures than a 10lb 8". How long the shell is, and how tight it fits in the gun are factors as well. I personally don't shoot anything heavier than a break and report from standard guns. That's probably on the conservative side, but I'd rather use a strong gun even if I don't need it than waste a shell and a tube. I do shoot long for caliber shells from normal guns, like lampares or beefy salutes, but I only use 2-3% of the shell weight for lift on those. Link to comment Share on other sites More sharing options...
Muslickz Posted October 6, 2020 Author Share Posted October 6, 2020 You guys are awesome, thanks for the informative answers.. I think I've got my lift percentage down now based 9n the quality of my BP.. -Mus Link to comment Share on other sites More sharing options...
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