tubes

[memo]

i have been having a hard time keeping my 3 "tubes from blowing the bung out or just plane blowing up.. my new idea is to wrap the tube in rope very tight then fiberglass over the rope the tube are hdpe. I am lifting multi break shells that are 1100 to 1800 grams in 3 inch, now I am building a 6 inch multi break. don't want to blow that one up. it cost a bit of money for the tube then shipping and import tax is a killer. tried making my own guns , I could never get the inside smooth enough to feel good about tube. this way using a hdpe tube as a base. building it up from there. I am open to thoughts. will this work ? the 6 inch shell will be in the ball park of 3000 grams. using the rule of thumb of 1 oz. per pound of course bp 2fa ?

 

memo

Edited August 23, 2016 by memo

[rogeryermaw]

Have you tried burying your mortars?

 

I read a lot about guys launching bigger shells insisting mortars for shells that large should be buried for safety. Should also add a ton of support to the tube and plug.

Edited August 23, 2016 by rogeryermaw

[NeighborJ]

I don't think that warping rope around it will work. In fact I believe the rope will squeeze the tube and once it is fired it may shrink the diameter, then it will be junk also. If I had to pick one thing to wrap it with, it would be a roll of aluminum flashing then just put a couple wraps of tape around that to keep it from unrolling. No epoxy or glue necessary. I think it better to get a steel tube for such heavy shells. Jerry rigging things can end badly.

[dagabu]

I don't think that warping rope around it will work. In fact I believe the rope will squeeze the tube and once it is fired it may shrink the diameter, then it will be junk also. If I had to pick one thing to wrap it with, it would be a roll of aluminum flashing then just put a couple wraps of tape around that to keep it from unrolling. No epoxy or glue necessary. I think it better to get a steel tube for such heavy shells. Jerry rigging things can end badly.

 

David F may jump in here as well but the flashing is an excellent idea! I have several tube supports for pressing rockets and they are made from 0.005" brass shim stock 100" long. Tighten the roll around the tube and press away! This should do as well for a mortar.

[memo]

trying to stay a way from metal, I could buy steel tubes, I really don't want to. I bury all my tubes that have salutes or multi break shells. I thought the rope would give the fiberglass something to grab ahold of when fiber glassing hdpe tubes. any other ideas that doesn't have metal involved ?

Edited August 23, 2016 by memo

[NeighborJ]

HDPE Polly pipe(gas line pipe). I don't launch many shells but I've never had one of these fail.

[memo]

I never had a standard hdpe tube ail until I started lifting multi break shells, they are heavy and a snug fit.

[NeighborJ]

My first tube was rolled up flashing and the logic behind it's safety was the fact that if it should ever fail the pieces of metal would be thin and foil like confetti. This is in stark contrast to the large shrapnel which a steel tube has the potential to create. The gas line pipe is much thicker and is fairly common around here but I have no idea of its availability in central America. Edited August 23, 2016 by NeighborJ

[Mumbles]

If you're importing anyway, have you considered getting fiberglass? I feel better about using it compared to HDPE for multibreaks. If you'd like I can upload some pictures of the long heavy HDPE guns from PGI. They're extra thick walled, and have very stout plugs. They seemed to work great for single fire shells. Reloading, not so much. Maybe you could get some ideas based on how they anchored the plugs and reinforced them.

[rogeryermaw]

I don't remember what thread it was in but the concept may have merit here: using a longer mortar with a slightly slower powder to allow chamber pressure to rise a touch more gradually may preserve your tubes and plugs.

[memo]

i have a bunch of tubes all ready imported, just trying to figure out a way to make what i have work.

[otto]

Just curious, how are you fastening the plugs into the tube? I'd for sure use some sort of epoxy with glass. rough up the tube a bit, I wouldn't even bother sanding on the plug. Schlorb it up good with 60 minute epoxy and add your screws or what ever. Heck when it's done you could even add additional glass around the base and under the plug. Just some glass cloth from an auto body store and good epoxy. Or even wrap with the flashing and glass over that.....

 

Lots of options with fiberglass.

[calebkessinger]

Put a 1/4in of resin and glass mat around that baby and let er rip !

I made some up for a few guys and have heard nothing but good things..
I made a multi salute mine where all but two of the salutes went off in the mortar so I'm convinced they are pretty strong.

[memo]

caleb there is no problem with the fiber glass sticking to the hdpe? it would be easy to ruff up. if that is all it would take, what kind of mat did you use ?

 

 

memo

[calebkessinger]

I used commercial mat. but you can buy perfectly serviceable stuff at an auto parts place. Boat repair. the woven mat like fabric is the way to go not the mess of mat like a rats nest.

 

If I was doing a hdpe tube I wouldn't worry a bunch about roughing it up.. clean it, rough it up if it's easy. Stick a rod in it and hold it horizontal securely.

Take the mat and cut it to barely overlap the top and hang over the bottom enough to reach past center. Then cut it long enough to do 3 complete wraps.

Wipe resin all over the gun, start your mat and get it stuck and do one wrap letting the rest hang down.. put more resin on till it's soaked.. wrap again, repeat. If that's not thick enough IMMEDIATELY hit it again with another piece of mat. Let the top part by the opening create a lip that grabs the tube. You can sand off the mess after it dries leaving a nice solid edge.

If you still feel like it's not man enough cut some 1in. strips that will wrap the tube 3 times and put one at the top edge. and a couple more down below the halfway mark ( aka combustion chamber )

 

after wrapping a bunch of standard fiberglass mortars and spending most of a week on them I finally figured out I had done them the slow way.. and came up with what I just described. Laid up a big gun that way and it went 100 times faster. It's the way I will be laying up any in the future.

[memo]

i will be giving that a go real soon, thanks for the info.

 

memo