27 replies to this topic

[RegimentalPyro]

So these fibreglass ones come from China...

Can't we (or someone who deals with such things) make our own?

I mean fibreglass is actually something we CAN get in this country without restrictions! (makes a nice change!) - you could even get your friendly local fibreglass molding company to knock one up for you and make up any story you want for ordering a tube. (Water feature in the garden )

How thick are the walls in such a device? Is it blocked at one end with anything?

On my recent trip to China I saw these being made. You can read a description of the process here

Edited by RegimentalPyro, 14 November 2006 - 03:32 PM.

[The_Djinn]

Shrubsole.. for what they cost, places such as MLE and Kimbolton sell these and they are not expensive.

[Frozentech]

Thanks for all the info everyone.

It is most interesting reading and I'm sure of help to those directly involved with shells and also those contemplating safely going into that area,

So basically, fibreglass tubes are best brought than made. (Unless you like sticky goo, irritating fibreglass and highly obnoxious vapours.)

But what of HDPE? - Apart from its weight, why is it way down on some people's lists? - Are there problems with it that you have found that everyone else needs to know about? In my very limited view on it, it should last a long long time (In NORMAL use) but what happens to it under unexpected blast conditions?

HDPE tears more than fragments, and is regarded as one of the safest possible materials for mortars. Iit stretches a bit before it fails, and the fragments are lighter and not as sharp, and unaerodynamic, so they don't fly very far.

[Night Owl]

Thanks for all the info everyone.

It is most interesting reading and I'm sure of help to those directly involved with shells and also those contemplating safely going into that area,

So basically, fibreglass tubes are best brought than made. (Unless you like sticky goo, irritating fibreglass and highly obnoxious vapours.)

But what of HDPE? - Apart from its weight, why is it way down on some people's lists? - Are there problems with it that you have found that everyone else needs to know about? In my very limited view on it, it should last a long long time (In NORMAL use) but what happens to it under unexpected blast conditions?

The only experience I’ve had with HDPE tubes are 8" and 10" ones with a 20mm dia wall, I didn’t like em simply because they where very heavy and seemed to build up condensation making them very slippery to carry, I ended up making carry straps and the 10" needed 2 people to carry them, that’s my reasons for not wanting to use them, paper tubes dipped in candle wax is my preferred method.

Edited by shell shooter man, 15 November 2006 - 02:40 PM.

[pyrotrev]

I generally use GRp for most purposes, except for sone of the pokier shells (e.g. long cylinders) where I'm moving over to HDPE. The rationale behind this is that various tests I've performed seem to indicate that such shells are more likely to detonate rather than flowerpot in a rigid GRP tube than the relatively flexible HDPE. BTW, true HDPE tubes aren't really that much heavier than GRP, don't confuse high strength HDPE with the softer (and hence thicker walled) MDPE varieties that are often used for gas/water in less critical applications. True HDPE water pipe is quite a dark blue and has much more of a ring to it when you tap it. I've just compared the weight of a 1 piece HDPE 4" mortar with a 4" GRP and they weight almost the exactly the same, whereas an old MDPE water pipe 4" is half as much again.

Edited by pyrotrev, 01 February 2007 - 12:48 PM.

[jimbo]

Some interesting reading here -

HDPE Mortar Testing-
http://www.pyropage.....vs.steel2.html

Ron Lancaster at Kimbolton seems to back them up, and yet his company uses fibreglass. Perhaps the cheapness and avalibality of fibreglass has swayed their decisions ?

[karlfoxman]

Kimbolton still have many HDPE tubes, I have used them for their shows and they have been around for a long time. Fiberglass tubes are cheaper and lighter, doing a show with 500+ shells is not fun if your having to carry around HDPE tubes. I love fiberglass tubes, oh and seamless steel ones for Maltese multi breaks!

[pyrotrev]

I've heard that extra-thick walled (and longer - ideal for your multibreaks Karl???) GRP tubes are available - has anyone tried them?

[pyromedic]

The main concern, as I see it, with fibreglass tubes is the fact that the fibreglass is degraded by sunlight.

At what point do they become too weak? There is no practical way of testing for this. At least when using paper you can see when the tube starts to degrade.

The fragments of tube are only one part of the safety issue. If the tube is part of a rack and it lets go...boom! then the whole rack can be affected (See Kimboltons recent accident).

[Mumbles]

I would think the most reliable method to check for degradation of fiberglass would be to watch for unravelling or fraying, or color changes such as fading or darkening. It's the outside that will degrade first from UV. All the sources I've seen use a colored epoxy with the fiberglass, oftentimes to indicate mortar diameter.

[pyrogearNoel]

We have done some testing on fiberglass mortars...

http://www.pyrogear....rglass_test.htm

What we have found, Both HDPE and Fiberglass will hold up to about the same amount of force, but the HDPE stretches and contains a lot of that force before transfering it to the surounding rack and tubes.

Schrapnel from the surounding rack was thrown considerably farther from the rack blown up with a fiberglass mortar.


If you are hand firing, HDPE is the safer choice.
If you E-fire and will not have any people in the shoot zone and have good safety distances for your crowd, then that downside to fiberglass is nullified.

As far as schrapnel from the fiberglass mortar itself, the pieces we found were soft and feathery and do not appear that they would be a threat to anything more than scratching you. HDPE gives no schrapnel.

Fiberglass usually has either a Resin or concrete plug, where HDPE will have a wood plug, both can fly out and hit a shooter, but no different than the rack pieces.

[cplmac]

I would definately take HDPE over everything else. The mortars stay basically in one piece when they get blown up. They will still send pieces of your rack and the other mortars flying, but the guns themselves pretty much stay in one grossly deformed piece.