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mortar tubes and associated projectiles


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Posted

Is the HDPE mortar tubes the same HDPE pipe that is used for plumbing? Lowe's sells 4" HDPE pipe in 10' lengths for $8USD. Compared to listed prices this is way cheap.

 

In the same vein, how much should 4" single break cannisters weigh? The way I figure it (probably wrong) with stars and break plus a comet or two somewhere in the neighborhood of 450-500g.

 

I have been trying to launch 4" sand filled shells with very little success. I can however launch a softball to LEO. I am figureing that I have too much weight in the cannister?

 

Any help/advise would be appreciated

 

 

Posted

What are the problems you've been having with lifting canisters?

 

Yeah, you can use pluming HDPE. Often it's heavier walled than fireworks tubes, which will make it slightly heavier, but that's not too big a problem.

 

While I rarely weigh my shells, half a kilo does sound about right for a 4" can.

Posted (edited)
Problems I have had........ hmmm with 0.75 oz lift can gets maybe 25', with 0.9oz tube blows to pieces, not sure where can went :unsure: . I have only tried twice as I was concerned that I was using the wrong tubes. The softballs, which I have not weighed, go on forever on .25oz. Edited by guntoteninfadel
Posted

Hey Infadel,

 

Are you sure it's HDPE? All I've ever seen at Lowes and Home Depot is PVC and ABS.

Posted (edited)
YUP, says so on the side! It is not with the regular water pipe it is with the sewage pipe. Without being able to take a pic it kind of looks like really thin pvc with a rubbery coating on the inside. And when I blew one up it did not splinter. I was just wondering if there was different grades, like pvc schd 40 and 80 because the stuff I bought is really flimsy. Edited by guntoteninfadel
Posted

My Lowes only carries ABS, looks similar but fits your description.

 

Most HDPE Mortars are made from plumbing/water pipe

The only HDPE mortars purpose made are Mighty-Mites and some 1.75" 1.4 stuff

Posted
Have you tried getting a purpose build 4" gun to see if it's just the tubing causing your issues? An HDPE tube should easily be able to stand up to an ounce of lift.
Posted
There are lots of variables. Could be your lift powder is too fast burning, try granulating it coarser so it gives a longer burn with a slower heave to get the shell accelerated without overpressuring the mortar. I wouldn't expect 0.9 ounces (25g) is enough to lift a 1 pound (450g) shell.
Posted

Thanks guys for all the input, I think I have answered my own question. The HDPE tubes sold as mortars seem to have .25" thick walls. Mine are nowhere near that thick. I think that would be the issue. I thought they were a little floppy looking when I bought the tube but hey it was $8! I only wish I had video of the failure! It was quite spectacular and a really good example of why to use HDPE in the first place.

 

later

Posted

There are a few different grades for HDPE. For 3" i would use hdpe DR15, for 4" and 5" DR21 is used. But the draw dack is most hardware stores do not carry the grade used for Pyro mortars. Here is a link for the different grades of HDPE

 

http://cavcovalve.com/Resources_files/hdpe%20pipe%20chart%201%20.pdf

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