The Use of ABS Pipe for Mortars

[LambentPyro]

I recently have seen images on here of ABS pipe being used for mortar tubes. IIRC, I saw a topic on PyroUniverse that using ABS is just as unsafe as using PVC. I never planned on using anything but HDPE, but for the sake of informing others searching through the forums, a quick Google search brought me here:

 

http://www.allsparkfireworks.com/blog/what-is-best-plastic-tube-to-launch-aerial-fireworks/

 

While the look and feel can be similar, it cant be stated strongly enough that other types of plastic pipe such as ABS and PVC must never be used to create mortar tubes. Even if an ABS or PVC pipe looks thick and durable, the inherent integrity of the plastic is much more brittle and can not hold up to the power of large explosions.

Edited February 6, 2014 by LambentPyro

[nater]

It has been discussed on this forum as well, recently in this thread: http://www.amateurpyro.com/forums/topic/9338-cato-or-flowerpot-efect/

 

HDPE, fiberglass and cardboard are the safest materials to use as a mortar. Due to the pressure generated when lifting heavy multi-breaks, steel is used since the others are not strong enough. When steel mortars are used, they should be buried 2/3 of their height deep and extra setback distance should be used. Fiberglass still poses a hazard to shooters. I've seen fiberglass mortars shatter similar to PVC, although the pieces don't travel nearly as far. Nessalco posted that he knows a shooter who required surgery to remove the fiberglass from him while handlighting. I still consider fiberglass "safe enough" and prefer fiberglass mortars in club events when mortars are reloaded several times throughout a night.

[LambentPyro]

Hmm, I didn't see that thread. I even searched for ABS and I got no results. Yea, I've seen videos where fiberglass mortars are shattered to pieces. Not a pretty thing...

 

Even for consumer shells, I load them into my HDPE mortar rack instead of using the fiberglass they provide. I keep it for extras or sometimes I just toss it out.

 

I believe you mentioned in that thread that HDPE softens when heated. When I was shooting 4" shells, after the first one went off, I grabbed it to turn it over to pour out any leftover debris in there and it didn't feel as solid and felt somewhat pliable; softer than usual. Could this lead to stretching of the mortar and produce stress at certain areas after constantly reloading shells? I wouldn't want a weak spot to build up in a mortar. If so, how many shells would it take in one shoot session to make a(n) HDPE mortar become a hazard?

Edited February 6, 2014 by LambentPyro

[bob]

Although I do not know for sure I highly doubt that firing one shell is going to make HDPE noticeably softer, I mean we have all used cardboard mortars and they don't burn up. With my steel mortars, right after firing they can be some what warmer than before, however it is barely noticeable, and certainly not enough to soften plastic.

Perhaps after ten shots in close recession the tube would be a little bit softened, the more experienced people on here will be able to give you a better idea of just how many shots it would take.

bob

Edited February 7, 2014 by bob

[mikeee]

HDPE pipe has a natural "soft" finish compared to ABS & PVC.

You can indent your finger nail into HDPE were as ABS & PVC have a very hard surface in comparison.

[marks265]

One problem with HDPE is that after time the muzzle ends sometimes close inward to give the appearance that too many paste wraps were used. After looking at a few they become obvious. I still prefer HDPE over fiberglass regardless of this. It might be the combination of age, time in the sun, and the amount of use that does this.

[nater]

After one shot, and HDPE mortar is usually warm to the touch. After several shots in succession, maybe waiting 60 seconds in between, they get hot and noticeable soft. For commercial shows, I prefer HDPE, it is more durable when being thrown around. I only prefer fiberglass when you are reloading all night long.

 

Fiberglass mortars also get chewed up around the muzzle end and the ring at the lip can get blown off after many shows worth of uses.

[LambentPyro]

I must have a cheaply made mortar then. My 4" tube was actually noticeably softer after the second shot.

 

That's interesting about the mortar's muzzle closing inward. After a few shots though when like that, it may expand back if the shell blasts through it hard enough if it was a somewhat tight fit (little more than snug) around the muzzle.

[leedrill]

Acrylonitrile butadiene styrene (ABS) it is unlike pvc in that it wont shatter as easily as pvc I.E. if hit with a hammer in the same thickness it wont just shatter like glass like pvc does abs is a touch more dense than pvc

 

its density { i could be wrong but is about that of hdpe }

 

abs gets used for such things as golf club heads due to its resistance to impact and can be impregnated with glass fibres similar to what comes out of a chopper gun for fiberglass spraying applications

 

abs is also used in 3d printers due to its stability at melting point and the temp at which it solidifies so you get very very little shrinkage or expansion

 

what i know about abs there is not much that suggest it to not be used { i will admit i have not read the thread that nater posted the link to yet }

 

but one thing is that when broken it will snap rather than tear at the weak point like hdpe {leggo products are injection moulded } for those of you whom have tortured many a gi joes and leggo men through out your child hood you will understand it is impact resistant but when broken it does not tear in the same way

 

i will add though makes me wonder about the 3d printed guns that have the governments worried lately which im lead to believe are abs plastic

 

anything is dangerous if the safety radius is not adhered to with scrutiny and you are shooting things like salutes but any dense plastics that have a property to break rater than tear open into just one piece i would not use

Edited February 9, 2014 by leedrill

[Arthur]

ALL tubes will break if overpressured, it's the mode of failure that matters.

PVC and ABS fail to small pieces of shrapnel which is dangerous if you are close

GRP fails to bigger pieces

HDPE fails to splits and expanded pipe but few if any fragments

Paper fails by ripping so a lot of energy is absorbed and the shreds of paper have little impact.

[mikeee]

The old style fiberglass resin used to shatter in pieces when it failed. The newer resins used for fiberglass tend to be more flexable and

when the mortar fails the fiberglass tends to tear much like paper releasing a lot of energy and the fiberglass pieces loose energy as they

hit the air much like cardboard.

[Wolverine]

Ever since my potato cannon literally blew up in my face when I was about 15, I haven't trusted PVC or ABS for firing anything out of. In the event of an accident they both produce a lot of shrapnel, it hurts like hell and could easily be lethal, I'm sure. Not to mention the Doctors have a hell of a time fishing it out. Trust me.
I've heard it said that if you are far enough away or behind bunkering it's ok, but IMHO they are foolish to use in any case when much safer materials are available.

Minimizing the inherent risks involved as much as is reasonably possible is of paramount importance and neither ABS nor PVC fit the bill.
My 2c as someone who never wants to have sharp plastic bits removed from him again and never wants to see/hear about anyone else go through anything like it.
I was a little hesitant to include my reason for my abhorrence of these plastics because it's embarrassing as hell, but if a little first hand testimony about the shrapnel helps prevent even one accident it's worth it.

[LambentPyro]

Wolverine, don't feel embarrassed, I think it was an excellent tip. Thanks for your input and sharing your experience.

[dan999ification]

Hdpe starts to melt at around 170 degrees, the edges will always soften before the centre of the material which explains mortars closing slightly.

It also swells while melting and contracts violently on cooling never returning to original shape.

 

It takes around half an hour at 170-210 degrees to soften 1" thick pieces in the oven you'd have to fire pretty fast to soften the inner material if its even possible.

 

Coloured hdpe is softer and stickier than clear and seems to soften quicker under heat, one of many other hobbies.. Recycling hdpe into usable objects, only mortar plugs are really relevant here.

 

Dan.