mortar tube sizes/thickness

[rev.redneck]

Hope this is the right place to ask, I searched but did not find the info i need. i have a tube that is 18 in. long, is that longer enough?

it is 3 1/2 OD. and 3 1/4 ID. Its hard and i can stand on it and it dont bend.

I put 1 Oz. BP in the tube, buried most the way in the ground, packed it full of newspaper and ignited with Ematch and it did not break the tube. I know its strong enough.

 

if i missed a post on this i apologize.

Thanx

[oskarchem]

It depends on what type of propellant you will be using...

[Mumbles]

The tube itself should be strong enough to survive the lift charge. It's just an odd size for shells. Most mortars are even 3", 4", etc. If you started shells on a 2 3/4" former, they would be fine though. The tube will be a good former to roll 4" shell casings on though. Or as bottom shots, but I won't get into that.

[rev.redneck]

Thanks, i was a llittle concerned about length. I have no problems with the shells. Plus i have alot of thes tubes. thanks

[aquaman]

If you are unsure that the tube is strong enough, test it. Plug the bottom with a plug that is as deep as the the inside diameter and put a dummy shell in it. If the tube remains unchanged, congrates you got a motar tube that will work, if not keep searching. Just make sure you test it where shrapnel won't hurt anything even if it is paper (better safe then sorry).

 

I find that making mortar tubes is as fun as lighting shells. I even make my own shells to fit my custom mortars. It takes a long time but at least I'm not dissapointed.

[oriansbelt]

Just make sure you test it where shrapnel won't hurt anything even if it is paper (better safe then sorry).

 

I find that making mortar tubes is as fun as lighting shells. I even make my own shells to fit my custom mortars. It takes a long time but at least I'm not dissapointed.

Yea, I can attest to that. I have a scar from some paper shrapnel that simply had enough velocity to mash my skin through my t-shirt when it hit. It was about a 1/2 in. square that was only about 7 layers think of normal paper at about 3 feet but it hit with enough force to @!%# up the skin under neath the cotton shirt I was wearing. I didn't do too much damage so it was in fact a good lesson for me since now I always wear safety gear just in case something I don't expect to fail does.

 

I'll have to agree with that too, custom mortars/shell are fun to make:). I haven't done much in that area yet so that is why I made all my stuff so far.

[rev.redneck]

I simply have access to alot of thes tubes, i can make the shells though, always do, i did test the tube as i said "I put 1 Oz. BP in the tube, buried most the way in the ground, packed it full of newspaper "

The tube erupted out of the ground throwing dirt every where, (not plugged enough on the bottom) i have a crapy cell phone vid of it in some kind of ".sg3" ? format. i burried it to ensure i have no horizontal shrapnel, just incase.

thanks for the input guys.

much appreciated.

[aquaman]

I believe (corect me if I'm wrong) that most mortars are pluged with wood that is screwed to the mortar. So it is like a oversized dowel rod that is as long, if not a little longer, than the ID of the mortar. Then is secured with screws and wood glue. For this one mortar I used a combination of a thin layer of gorilla glue (love this stuff) and paper towels and then a much thicker layer of durhams rock hard water putty. Once all that hardened I screwed right into the putty. Bam it's pluged. The only problem is the gorilla glue is damn expensive.

 

Have fun and stay green.

[Deafaid]

I've a cardboard tube and its 4 OD and 3 ID.

and the tube doesn't have an end plug.

What could i use for an endplug? not a wood endplug.

[deadman]

Why can't it be a wooden plug? If you are having trouble finding a wood plug you can make one by cutting wooden disks and gluing them together.

[Berksglh]

For the end plug, How about taking a piece of un split firewood (large branch) with the right outer diameter, and cut a piece off long enough to plug the end of the tube.

 

I don’t have the tools to cut a square piece of wood to fit a round hole either, so I would try to find something round that fits, then chainsaw, circular saw, or hand saw a piece off.

 

I see no reason why it wouldn't work?

[rev.redneck]

I'v seen a jigSaw at a store recently for about $15, probably come with blades. cut a piece from lumber, thats wht I would

 

You could try to wood glue a lot of round pieces of cardboard in the bottom.

 

i'd use wood though..

[tentacles]

If you had a bigass rammer, you could just ram a couple inches of clay in there, or something. Alternatives could be ramming strips of glue wetted kraft paper in the bottom like an inch or two thick. Obviously you would want to test the plugging method but either could be viable.

[jacob]

You might try glueing it to a base and puting in some screws at an angle trough the outside of the tube and into the wood, i've done this before and it was pretty stong. if that won't work for you then then you could try concrete .

[Deafaid]

Finally I found this:

http://static.gooba.no/Image/Products/Large/ZUCO105800.jpg

 

thats perfect for making end plugs......

[TheSidewinder]

You may find that very difficult, unless you use it in a sturdy drill press with the wood stock clamped down.

 

I tried much the same thing, without a press or clamping, and for the life of me I couldn't cut two plugs the same size.

 

Don't wish to be negative, just warn you that it's not as easy as it may seem.

 

M

[pudidotdk]

A drill press is pretty good for those drillbits, that's what I use and It works smoothly. I almost never uses a regular drill anymore....

[Deafaid]

I have a problem.....

The drillbit maked an end plug of 74 mm and the

cardboard mortar has a 76 (3") mm hole...

so the drillbit is to small.....

what can i do to make the 74 mm end plug to fit in the tube?

any suggestions?

[hst45]

Use your holesaw to cut a plug the next size smaller than the inside diameter of the tube. Take some strips of kraft paper, paste them up like you're pasting a shell, and wrap them around the circumference of the plug until it's a snug fit in the tube. If you have access to "gorilla glue" use this to glue the plug in the base; the bond is stronger than the paper OR the wood. It's pretty easy once you get the hang of it, and only takes a couple of minutes.

[Deafaid]

thanks for helping me, hst45 and bluesquib.......i'll try it today.

[hst45]

hst, we mean the same method - but I have to aknowledge ungrudgingly: you explained it waaaay better than I did.  Thanks.

No problem; I have the advantage of English as my native language. Well, American actually, but its pretty close to English.

 

I have to tell you, I have a great deal of admiration for you Bluesquib, as well as some other members such as Pudi, Pretty Green Flames, Brainfever, etc., for being able to translate pyro into English. I only speak a bit of converstaional French and some Spanish, and in these I could never carry on an intelligent discussion of the technical stuff we discuss here. I am glad you make the effort, as your input and information is appreciated.

 

By the way... it's been snowing here today, it's going down to 12 degrees F tonight...wow, such Global Warning.....(inside joke ).

[Ventsi]

Just curious here, I have some 3" multibreaks that I need to shoot, and instead of using 1/2" walled paper tubes I decided to go with steel.

What is an appropriate wall thickness?

[dagabu]

Touchy subject here Ventsi, the steel thickness is not as important and the method of construction and steel type. If you use welded pipe, it is only a matter of time before you blow the gun up. Also, I have seen a lot of broken pipe that looks good but is cast and the weld breaks right off leaving the to come out of the ground or worse yet, it will shatter and sent pieces all over the place.

 

What you are looking for is high pressure gas pipe, ASTM A106 Seamless Pressure Pipe (also known as ASME SA106 pipe). You will also need someone with the ability to weld the caps into the pipe at least 2X the wall thickness into the pipe end. Lastly, you need to follow the NFPA 1123,1124,1126 code for burying the guns, in Minnesota we have to bury the guns 3/4 the way into the ground. This forces a failed gun to push the ground out of the way, absorbing much of the energy and allowing the the shrapnel to up rather then out, hard hats help a lot in this situation.

[Arthur]

In Malta they launch all their shells from steel mortars, but in the UK metal mortars are a certain NO NO.

 

The UK theory behind the idea is that any metal mortar will eventually fail catastrophically forming 20 kilos of metal shrapnel so a 2" would be a hand grenade and a 4" an anti personnel mine and so on....

We use GRP (fibreglass) for routine work, also paper and HDPE.

[dagabu]

Arthur, Multibreaks cannot be shot from anything but steel. Show me close proximity video of a successful (out of the barrel and in the sky) 4" or larger 4 break or more shell fired from anything but steel and I will send you 1000 cap plugs for free, shipping included to the UK.

 

Side note: Please, nobody try this, we do annual training on safe use of tubes, this is my camera recording a 3" salute in HDPE in a well constructed rack. The camera takes a direct hit, it is armored, it was not hurt

 

http://pyrobin.com/files/modular%20rack%20test%20salute.wmv