Mortar Tubes

[fatcat]

Just sitting here and have been re reading some of the threads and came up with a couple of questions.
On the 1.3 side of the fence, is there a standard length of mortar (gun) used in the professionial side of the pyro world depending on the size of the shell. I guess I could change it and ask it this way, does the length of the gun effect the shell's performance? (Remember we are talking Pyro)
On the 1.4 side of the pyro world, apparently there are basically 2 lengths of guns used in racks, 12 inch and 15 inch. Seems like most shells if used in 15 inch guns need some fuse added to them. Some folks have suggested in the 15 inch guns drilling holes about 3 inches from the top and running the fuse through the hole. Anybody do this and has it affected the guns structural integrity? Your comments.

[pyro man 205]

I shoot 1.4 i have 80 15in fiberglass tubes, 15 12 hdpe tubes and 218 hdpe 15 in tubes. if the shells have a short fuse i use my 12 tubes. most of my shells i shoot from the kits have a 15 to 11 in tubes. now it is not really 15in in side, you have 1in plug in side or a 1in half. so your tube would be 14 to 13 in in side, now the same with 12in tubes would be 10 or 11in in side. now for holes in the tubes no i do not do that at all. back when i started making my racks 05/06 some said 15in would make it go higher ????? well on some. then most good shells come with the a tube with in side length of 11in or 13in hope this helps you out?

[notenoughcash]

NFPA 1123 A.4.3.8 is a table which will give you a recommended minimum inside length of a mortar (3"-12" shells) with provisions for single, double, up to four break shells. Can't remember right now on plug thickness minimums but you'll need that also to determine overall length of tube, assuming HDPE

[indianahx]

Kudos for actually doing the research beforehand.....I have heard the same about making them go higher. That said, I have also heard the do nothing to increase height. Id love to see a test of this with MANY MANY MANY side by side shot comparisons.....but then again there are so many variables

[Pyro_Rich]

977 I've attached a copy of NFPA 1123 Table A.4.3.8

[PyroJoeNEPA]

Easy "rule of thumb" for gun length is 6" length per inch of shell--so, 3" shell, 18" gun, 4" shell, 24" gun, 5" shell, 30" gun, 6" shell, 36" gun...etc.
I have yet to see anything from anyone that documents a longer gun giving a shell any extra height. It will certainly help in trajectory--like the difference in a 357 pistol with a 3" barrel compared to the came caliber with a 6" barre.
Relative to tube length--look at the length of the monster cylinder shells they shoot in Malta--some of them are 5 feet long and just barely fit down inside of the gun--but they do get up in the air!!! So I woud say it is not a big a deal as someone would make it. No need to overthink some stuff!
Also, on the "drill a fuse 3" down from the top U run the fuse out the hole"---the hole will not affect the integrity of the tube--but why bother? use shorter guns or shells with longer fuses.

[ilovecrackle]

Easy "rule of thumb" for gun length is 6" length per inch of shell--so, 3" shell, 18" gun, 4" shell, 24" gun, 5" shell, 30" gun, 6" shell, 36" gun...etc.
I have yet to see anything from anyone that documents a longer gun giving a shell any extra height. It will certainly help in trajectory--like the difference in a 357 pistol with a 3" barrel compared to the came caliber with a 6" barre.
Relative to tube length--look at the length of the monster cylinder shells they shoot in Malta--some of them are 5 feet long and just barely fit down inside of the gun--but they do get up in the air!!! So I woud say it is not a big a deal as someone would make it. No need to overthink some stuff!
Also, on the "drill a fuse 3" down from the top U run the fuse out the hole"---the hole will not affect the integrity of the tube--but why bother? use shorter guns or shells with longer fuses.

Years ago I bought a couple 15" tubes to see if in fact a shell would go a little higher than being shot out of a 12" tube. Me personally, I noticed absolutely no difference in height.
I tried numerous brands of shells, shooting one at a time, shooting side by side.... absolutely no difference that i could see.
Others may have experienced different results, me, no difference.

[Pyro_Rich]

Very Interesting, and good example. Trajectory may improve with less tumble, etc. But does it really improve height? That's a good question. Less roll and tumble is factor with rifled barrels but were shooting from smooth bores. I would 'guess' a longer smooth bore barrel will shoot higher and more accurately than a short than a sorter one as the shell has more time to stabilize on before it reaches the muzzle. If that taken to the extreme the shell will also slow down to an extent.

So let's say the difference in gun length is for a 3" shell goes from 18" to 12" and with a 10 mph wind, the shell fired from the smaller gun may not reach as high as the shell sot from the longer gun. Yet this difference in height may not even be noticeable from the shooter on the ground. Will the trajectory be different - absolutely! Were obviously shooting fireworks and not aiming out shells at thumbtacks 200 yards away. The NFPA sets codes for safety and I choose to follow it.

Another thing to consider is liability, the NFPA sets codes and guidelines which are accepted as safe. Should an operator decide to disregard the NFPA and should there be an incident where someone gets hurt, killed or where property damage is involved not only will the display company, the sponsor, the property owner be sued. You can also be sued or even criminally charged for reckless endangerment or maybe even criminally negligent homicide.

Over regulation to an extreme can be a bad thing but, as far as the NFPA and fireworks are concerned I totally agree with them and follow all the rules.

[PyroJoeNEPA]

Trajectory may improve with less tumble, etc. But does it really improve height? That's a good question. Less roll and tumble is factor with rifled barrels but were shooting from smooth bores. I would 'guess' a longer smooth bore barrel will shoot higher and more accurately than a short than a sorter one as the shell has more time to stabilize on before it reaches the muzzle. If that taken to the extreme the shell will also slow down to an extent.
Another thing to take into consideration--[talking 1.4g consumer shells now] The lift charge & time fuse are whatever the factory makes them to be. The lift maa be strong enough to get the shell higher but the time fuse will pop the shell at a fixed point in time relative to the time fuse length. Also, the lift charge might be lighter & the shell may not go as high before breaking. The "optimum" would be for the shell to break just before it hits its apogee and begins to turn downward.
Interesting thread guys!

[Pyro@Mach13]

Very good point Joe.

[Rick_In_Tampa]

A longer HDPE tube will NOT make a shell go higher in the air, any more than a longer barrel on a gun will make a bullet go any further. It's simple ballistics. The height of the shell is dictated by the size of the lift charge, the wind speed, and other factors like humidity, temperature, barometric pressure, etc. (if you really want to geek up the calculations). If anything, I would argue that a longer tube DECREASES the height as the longer tube represents a greater resistance path for the shell as it leaves the tube. Are you going to notice the decrease? No. We're talking inches, not feet. Hope this helps.

[ras1986]

A longer HDPE tube will NOT make a shell go higher in the air, any more than a longer barrel on a gun will make a bullet go any further. It's simple ballistics. The height of the shell is dictated by the size of the lift charge, the wind speed, and other factors like humidity, temperature, barometric pressure, etc. (if you really want to geek up the calculations). If anything, I would argue that a longer tube DECREASES the height as the longer tube represents a greater resistance path for the shell as it leaves the tube. Are you going to notice the decrease? No. We're talking inches, not feet. Hope this helps.
Shoot a canister out of an 8 inch mine tube and then tell me length won't make it go higher.

[Westpapyro]

I've heard of people saying they have some 15 in. mortars that send shells higher, only to look into it further and find they were not hdpe they were fiberglass? I think it had more to do with the size (width) of the shell, in the smaller tube with less gas escaping on the sides put more force on the shell upwards. Not tight enough to cause friction or resistance. We've probably all seen some shells are very sloppy in hdpe which gives a slightly lower break? But as stated above there are many variables that determine shell height?
I drill holes in all my 1.3 mortars for ematch tie off!

[Rick_In_Tampa]

As opposed to what? What's your theory as to why you believe it goes higher?

[nypyrochef1.3]

What Rick said^ more lift charge more hight. Other things can affect this tho but not so much tube lengths. Use the correct lengths. They are there for a reason. If u want higher lifts u can have shells custom made for it.dont forget the time fuse has to be correct also to
Match the desired lift hight.