Mortars

[Mardec]

Hey, I recently upgraded to making 4" shells

 

But now I face new problems. For 3" a cardboard tube with heavy dute PU glue and beam of would to glue it to would work fine. This is not really plugging but it works.

 

But now I have a 4" hdpe tube wich I cannot glue to a wooden beam. That will deffinately not hold. I cannot plug it either because I have nog matching plug.

 

So I am going to dig it in. But in order to do that. Should I still plug the tube or can I just dig it in there with the bottom side "open".

 

I have no experience with digging mortars in..

 

Sorry if this has been coverd, but searching the forum did not result in finding what I wanted to know.

[Mumbles]

Yes, still plug the mortar. If you don't the lift gases will expand the ground underneath the mortar and not lift as high. At a show I was shooting I saw a 6" shell blow the bottom off a mortar that was dug in. It went maybe 1/3 as high and apparantly left a big hole in the ground underneath. I also used to use a cardboard tube in a bucket of clay for firing, no bottom. I've had shell shoot out a bunch of clay from the power of the lift. I now use good HDPE mortars though.

 

You'll want to bury the mortar about 2/3 to 3/4 of the way down into the ground. A post hole diger or an auger really expedites the process.

[hst45]

If you have access to a good selection of carpentry tools, a holesaw can be used to make great wooden base plugs. The holesaw I'm describing is essentially a drill bit with a serrated ring of metal around the perimeter which cuts into the face of a block of wood. They come in many sizes. The circle of wood they they cut out is normally discarded, but in my case it's saved and glued into the base of the mortar. Some additional sanding may be required to make it fit. I find this a hell of a lot easier than trying to free-hand a circular plug on the scrollsaw.

 

I've make up a number of tubes, and I've fabricated a firing base which consists of a plywood plate with a series of screws protruding upwards. Pre-load a mortar, thread the mortar down onto the screw, and you're ready to go. I only do small shells, so the tubes are 2", 2-1/2", and 3-1/2", so I don't really feel the need to bury the mortar, so this setup works great for me.

[Tweetybird88]

Would it be possible to put a mortar in a bucket and fill the bucket with sand to anchor it? I would assume that it would work up to a certain size.

[hst45]

Sure it would be possible, but it would be preferable to have a sealed base. You want to seal in the gas from the lift charge, and permeable material like sand will allow it to dissipate as Mumbles said. If nothing else, maybe you could wrap several layers of duct tape over the end of the tube and then bury it in a bucket of sand. This would burn out after a few shots, but it would be better than nothing.

[cplmac]

You could also order a plug from midwest. Don't know if they sell plugs by the ones, but they might. And I'm sure they would be happy to help. If you bury your mortar try to make sure it is resting on a large rock in the bottom of the hole, preferably one that is larger than the OD of the mortar. This will really help keep the ground from absorbing the energy. It will also make life much easier when you need to retrieve your gun. I've spent almost an hour before on buried 8 and ten inch mortars that were in wet ground trying to coax them out.

[ns4life]

I had to plug a five inch tube and found at the arts and craft store they had thick 5 inch disks that fit perfectly.

[Mumbles]

Midwest says no minimum order, though they give standard case sizes for optimum shipping efficiency.

 

http://www.mhtc.net/~mws/

[tentacles]

Someone mentioned buying a holesaw and using that to make plugs - if you're going to buy something to do it, buy a "circle cutter". It does exactly what the name suggests, cuts circles of material with or without a pilot bit - if you omit the pilot bit, be sure the wood is very securely clamped! The one i have is adjustable from like 1 3/4" - 8"

[rocket]

If you have access to a wood lave you could use that to turn an end plug. That is how I plug all my mortars, I make the plug that tiny bit to big so you have to ram it in with a hammer.

[ActionTekJackson]

I just free handed a circle with a Jigsaw and sanded it down to fit just right. It's alot of work, but most people already have the tools to do it this way, or you probably know someone who has them. If you can, just order it.