Author Topic: [maybe dumb] noobie Q's... looking to build cheap and safe (Read 1102 times)

mortarnoobie · « **on:** April 24, 2005, 06:12:35 PM »

hi everyone.. i'm new to the board as you probably know. i stumbled upon it while surfing the web for information about how a friend and i could build a mortar that won't go and fall apart on us, but still be pretty cheap.
I have seen a lot of absolutely beautiful projects that you folks are working on here... not what our aim is. i built a simple PVC potato cannon, and after using it for a while and reading about the relatively high cost for [what i would consider] not very much gain in performance to build a new one [and after the spud gun board got sorta mad at me for discussing high power fuels], i started lookin around for powerful option.

we want to design [or use someone elses design] and build a gun from the most inexpensive materials that still won't blow up on us. We would probably shoot golf balls and/or similar sized ball bearings or even beer cans, or whatever would come the closest to fitting in a pipe. so someone hit me with some numbers and pipe diameters and steel types and stuff like that that i should look for. is pipe strong enough for a simple mortar like this available at a hardware store? we can get welding done on it to weld a cap on the end... turning would probably be hard to get done though.

my noob mentality here is that if the bowling ball mortars that people construct out of 1/2 - 3/4" thick pipe can withstand the astro. force of chucking something that heavy, won't a properly welded pipe of smaller proportions do the job just as well (without looking as pretty as you guys' things of course)?

thanks to all who can fill in a novice in need (er... want) on the basics of what appears to be a really fun hobby.

PS: i saw the announcement for the golfball mortar contest... is that pipe already the right size dia.? could i get some of that? i'm not sure if i'd have it ready by september... would i have to purchase the materials if i was not going to be able to participate in the actual contest?

thanks again!
-Jon

CAV Trooper · « **Reply #1 on:** April 25, 2005, 11:38:26 AM »

Jon,

No matter what the "potato gun" sites say, stay FAR away from PVC when building ANY sort of cannon. It only takes a couple of hundred pounds per square inch of pressure to turn PVC into a bomb. "Spud guns" can, and have, exploded by using hairspray for propellent. Using anything else is a disaster looking for a place to happen.

Welded seam iron or steel pipe that you find at places like a plumbing supply store, Lowes or Home Depot isn't strong enough either.

This site is devoted to black powder cannons and mortars that are constructed properly and fired safely. From your post, I get the idea that what you want to build is a fancy "spud gun".

I may be wrong but I doubt if anybody here will give you any info on building something like that. I certainly won't.

Building a functional cannon or mortar IS NOT something that is done using "the most inexpensive materials". You obviously haven't seen what an explosion will do to a person but I have. Trust me, you REALLY DON'T want to go there. Saying that it will ruin your whole day is probably the worlds greatest understatement.

Besides the obvious safety issues involved with your project, what it sounds like you propose building could likely be considered by the BATFE to be a "Destructive Device". Building or possessing such an item without FIRST getting approval from them to do so, could result in a fine of up to $250,000 and up to 10 years in Federal prison.

This obviously isn't the answer you're looking for but all I can say is: sorry about that.

If I'm incorrect in interpreting your intentions, let us know and we'll go from there.

Cat Whisperer · « **Reply #2 on:** April 25, 2005, 12:37:20 PM »

'noobie -

WELCOME to the forum!

Cav Trooper is stearing you right. I've often said here there are 3 rules, keep it safe, keep it legal and have fun.

Your best bet is to do a mortar of Southern style - simple in design and gets the job done. Definitely do a powder chamber - to increase the thickness of the steel.

The steel we provided for the contest is 1144 stress proof DOM tubing of 2" OD and 1.495" ID which must be bored out to about 1.700 or 1.750 for golf balls. AND something be machined (like the provided round of 1144sp) to act as a breach plug. 1144sp doesn't weld well (cracking) if not done by a certified welder - even then I'd avoid welding.

You're right in your thinking about considering caliber as a function of readily available ammo.

Keep looking for materials and resources. You often stumble into things that you'd not think twice about but for the fact that you're in-the-hunt for materials for a beer-can launcher.

I speak from the experience of having seen a cannon explode from 15' away. I'll say it yet again, when you light the fuse you need to KNOW whether it's a bomb or a cannon.

CU_Cannon · « **Reply #3 on:** April 25, 2005, 12:47:54 PM »

Welcome,

By coming here it seems like you do have some good intensions but CAV brought up some good points. If all you want is something that goes bang you should go else ware. No one wants to discourage you but this is a reputable board that no one wants to see shut down.

That being said I'm not sure what you would be able to build anything safe without a lathe. You could build a safe and reliable golf ball mortar for around $50 - $100 depending on how good you are at scrounging and how much work you can do your self.

Do not build a mortar that is a pipe with an end cap welded on. Best case it would be considered a destructive device there for illegal. Worst case it would be a pipe bomb.

If you tell more about your intensions I'm sure you will find lots of help.

mortarnoobie · « **Reply #4 on:** April 25, 2005, 12:56:54 PM »

CAV Trooper, you misinterpreted. by inexpensive materials, i'm saying that i don't want to build a gleaming detailed replica of a gun used in war. I have no intention of using pvc for anything like this. it was simply a quick explanation of how i found an interest to build a mortar. i don't want to build 'makeshift', just not very fancy.

regarding the golfball mortar contest and materials offered to build it... i could get it turned to the proper inner diameter if necessary... i was just saying i don't want to be doing a lot of it. as for not welding it... how else would you put it together? it sounds like this would be a good starting point for me us build with. am i right? we could get it welded at a shop and turned. does anyone have a CAD drawing of a basic design of how they put theirs together and stuff?

as for safety, legalities, and such. someone that i went to school with has offered the use of his land (30 acres i think... not to sure but ya, its private property). he's got a quad that we could run from this thing on during the test firing to get out of its potential kill radius too.

any other questions let me know. like my name says i don't know everything about this stuff. do i have some misinterpretations? yes. am i willing and eager to learn? for sure

thanks
-Jon

Cat Whisperer · « **Reply #5 on:** April 25, 2005, 01:29:05 PM »

Jon -

We're cool. It's easy to mis-interpret things written in emails and posts anywhere.

One issue of making a mortar (or cannon) is that of sealing the breach plug in such a manner that is secure AND leaks NOTHING that would corrode (over time) and produce cracks.

Look at the several designs that have been posted thus far (it's a contest so some are waiting for the unveiling till later).

I took the low-budget k.i.s.s. design and side-stepped the problem of having to have a gas-tight seal by making mine so it could be disassembled each time after firing. You'll see a couple of pictures here: http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=60829 .

If you have to pay (a four letter word) for machine work to be done, like boring a tube, you might as well have a solid chunk of steel bored to 4 or 5 inches deep (recommend two diameters deep - 3.5").

Your best bet now is to read. There is a wealth of experience being aired here with some great pictures. You will find good links as well. AND there is a variety of perspectives - that is but one test of the quality of ideas - peer review.

There are folks here that have produced motars/cannons for little more than the time invested with some relatively crude equipment (and they have earned MY respect) .

And there are the obvious masters of the trade, our sponsor, a fellow who teaches cannon making, and several machinists.

You've met a few of us, keep asking questions and bringing up ideas. There are ideas you'll bring up that will be most interesting.

CU_Cannon · « **Reply #6 on:** April 25, 2005, 01:55:38 PM »

Well, it sounds like you are worthy. :wink:

I would start out with a golf ball mortar. They are lots of fun relatively easy, quick and cheep to build. For something well over built start out with a piece of 4" solid about 7" or 8" long. 1018 steel would be ok for golf balls 4130 would be better if you want to shoot lead. The bore should be 1.72" to 1.75" with a 1" by 1" powder chamber. To attach the barrel to a base you could drill a couple of holes and attach it with bolts or for something more like a coehorn weld a piece of 1.5" steel across the bottom. Hope this helps.

Double D · « **Reply #7 on:** April 25, 2005, 01:56:17 PM »

I ain't calling nobody stupidnoobie.

Jon,

We aren't going help you hurt yourself or any one else. We will share our ideas and help you learn why we are so guarded about what we do..

Got to our resource board at the top of the forum and look over what is there. Cruise through posts on our board and get some ideas what you ar dealing with. If you look long enough you will find the answer to every question you asked.

A good first project is a beer can mortar. Several of the fellows here have theme. You don't have to build a scale model but you do need a replica of a pre 1899 gun to be legal. The beer can mortar is a replica of a Coehorn mortar.

What's a beer can mortar? Check google, look at our resource list.

Find your plans and start asking questions.

Just for the record I found a way to builds a mortar for the contest without welding. I ain't telling how how until the contest closes or after this Thursday when I go test it and it fails.

mortarnoobie · « **Reply #8 on:** April 25, 2005, 02:17:14 PM »

cat
read through the page that you linked me to and i like what i see: pretty simple :grin: the tube is a piece of pipe as opposed to a solid piece of stock which you turned from scratch, correct? i imagine that having someone do turning for me wouldn't be terribly cheap, so starting from pipe instead of stock would be the better way to go for me (right?).

assuming that it is pipe, is it similar to the materials supplied for the golfball mortar contest? could i construct one similar to yours from those materials (given that i could get turning and drilling done of course)

CU_cannon
thanks for your tips as well. for bolting the base on... your referring to what is in cat's link, right? this looks kind of handy... makes for easier cleaning and oiling and what not. i do own a drill press for drilling metal, so i could do this.

Double D
thanks for your concern for myself and others. about the beer can mortar, i think i'd be better off starting with a smaller bore, for price and safety sake (from what i've read, larger bore increases risk of a gun failure pretty decently). i'd rather go with golfball for now. o, and about not revealing your way of doing the golfball mortar without welding, if you could PM or email it to me, you have absolutely nothing to fear for me somehow outdoing you in the contest (haha i wish). All i'm looking for right now is reliability, simplicity of construction, safety, and fun

one more thing; i don't mean to sound pushy or anything, but what kind of distance could i expect to attain from one of these? I have read on plenty of sites and a few personal web pages about golfball mortars acheiving up to 400 yds. are these distances only safely attained with the mortars turned from solid steel, as opposed to the one in the link cat posted?

CU_Cannon · « **Reply #9 on:** April 25, 2005, 02:25:26 PM »

Here is a quick drawing of what IÂ’m talking about. If possible avoid sharp corners at the bottom of the bore. The bottom of the barrel could be ground of turned to give a more rounded shape.

mortarnoobie · « **Reply #10 on:** April 25, 2005, 02:31:42 PM »

those are the type i was referring to in comparrison to the one Cat posted the link for. http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=60829 so you don't have to go back to it

is there any disadvantage to cat's cannon over the one in your CAD, aside from looks and all? Is your CAD one for some reason legal and his is not? is it stronger? (as in extra usable strength)

this is my concern. I would like to go simple with a pipe and end cap (welded or bolted... whatever), but not if i am sacrificing safety, distance, and things like that.

Cat Whisperer · « **Reply #11 on:** April 25, 2005, 03:03:39 PM »

Jon -

I much perfer (for strength and design) one piece solid steel. Some folks will cast the tubes, but I tend to over build. I have one golf-ball caliber mortar of 1018 that is 5" in diameter - looks like the Dictator. Haven't built a base for it yet.

The tubing shown is DOM - drawn over mandrel - which is very precise in dimension and being made of 1144sp is VERY strong (100,000psi tensile strength). It also turns very well and the price was exactly right for a number of pieces (free). It is SEAMLESS which is important - strength.

One principle was developed by Coehorn in the 1700's - thick around a powder chamber (pressure peak is early in the burn) and that allowed thin in the rest of the tube - making a light-weight big bore mortar.

If you bore your own, put a radius in every place possible - a sharp corner is a stress point (especially at the inside bottom of the bore) and make a powder chamber.

The expense in machining is the setup time. Boring does take some time but it allows you a lot of options in design.

CU_Cannon drew up a good plan for you.

Range - here are a few pix of a hand-held (hand gonne - style from the 1100's) http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=23881&highlight=hand+gonne . You will see that it doesn't really kick that much and it's easy with a small amount of powder (in a 2 golf-ball deep bore) to get 100 to 200 yards. 400 should be easier than you want.

CU_Cannon · « **Reply #12 on:** April 25, 2005, 03:34:51 PM »

They are both legal as far as I can tell. When I said that a pipe would be considered a destructive device I was referring to something more like a Stokes Mortar. Both would be models of coehorn mortars. There are several posts on the board discussing legality issues.

As far as safety is concerned both designs appear to be safe. All my mortars have been machined from solid so I canÂ’t comment designs involving a breach plug. You may be able to get away with just a drill press if you can get a hold of some big drills. You could drill the bore to 1 3/4Â”. It would be a some what loose bore but it would work. The looser bore would lower the pressure making it some what safer but distance would also be lower.

IÂ’m not sure what the price of machining is on a project like this.

Quote from: CW

CU_Cannon drew up a good plan for you.

It does look a little like your avatar. :wink:

mortarnoobie · « **Reply #13 on:** April 25, 2005, 04:09:44 PM »

i think the reason i'd go with a tube instead of solid steel is because it's a first gun, and probably isn't going to be perfect anyway. in the future, i'd love to construct a beer can mortar of solid steel complete with hand made steel and oak sled, etc, and with a powder chamber massive enough to send the darn thing outa sight. As you probably see from my posts, i don't have the resources or knowledge to do that very well right now.

Cat thanks for the tip on the drawn over mandrel. i will do some browsing for it. it looks to be 1/4" thick or so...? is your breech plug of the same material? i assume you machined the powder chamber. a larger powder chamber would leave room to expand to larger charges in the future, correct? (working up to such things of course)

thanks for the knowledge as well as the prompt replies (=
-Jon

Cat Whisperer · « **Reply #14 on:** April 25, 2005, 04:30:20 PM »

Here's one I had made of 4140 from 4" diameter:

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Here are a few details from one of the DOM tubing golf-ballers:

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and one (golf-ball caliber) of 5" dia 1018 steel still warm from welding the trunions in place:

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Lots of options, Jon. Your toughest job will be choosing.

mortarnoobie · « **Reply #15 on:** April 26, 2005, 02:25:22 PM »

cat, did you turn the front part of the barrel to a thinner wall than the back? i think i see it now... this way it wouldn't have to be incredibly tight of a fit, and the difference in barrel size would keep the plug from shooting out the back, right? if this is what you did, i like it... do you even have to have a bolt or anything holding the plug in?? if i'm looking at the picture right, you must not need mroe than a small screw to keep the fuse holes in line with eachother.

Cat Whisperer · « **Reply #16 on:** April 26, 2005, 03:52:41 PM »

Quote from: stupidnoobie

cat, did you turn the front part of the barrel to a thinner wall than the back? i think i see it now... this way it wouldn't have to be incredibly tight of a fit, and the difference in barrel size would keep the plug from shooting out the back, right? if this is what you did, i like it... do you even have to have a bolt or anything holding the plug in?? if i'm looking at the picture right, you must not need mroe than a small screw to keep the fuse holes in line with eachother.

I think you've got it. Here's a shot of some playing around.
On the left is a fire-cracker golf-ball launcher. Short range only.
The others are musings on the theme of two-piece tube and breach plug assemblies. Again, I'd prefer to use one-piece construction, but this is part of the exploration of ideas in the golf-ball mortar making contest.

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Double D · « **Reply #17 on:** April 26, 2005, 04:27:18 PM »

Hey your stealing my ideas!!!

Cat Whisperer · « **Reply #18 on:** April 26, 2005, 04:38:27 PM »

Quote from: Double D

Hey your stealing my ideas!!!

Ya gets 'em where you can!

Still have a few more to try. I like the one on the right, but it's not as neat and simple as I want yet. Set screw pushes off-center on the trunion locking the three pieces up tight. (Forces the trunion forward and the breach block back (trunion against the tube and pulls the breach block back sealing on the larger diameter of the breach block against the smaller diameter inside the tube.) I'll probably move the setscrew to the back so it will be completely hidden.