please take a look at my cannon idea/progress so far

[mortarnoobie]

well after going over my options of building a blackpowder launcher, what i wanted to do with it, how much i was willing to spend, etc., i started calling every metal shop in my area, and found a real pot of gold.  




1/4" (actually a little thicker) drawn over mandrel steel that surely is.  2.5' of it.  the folks at this shop were great.. they asked what we wanted this for, and when we hesitated, they said 'o your building a cannon... this is the thing for you.  i used it for mine and its strong as sh**'.  they even stayed open late so we could get it.

now they threw in that block with it to weld on for free (they didn't have time so i'm going back tomorrow), but i am wondering if it is big enough around or if i should get one that covers the whole end of the pipe.  

dia. is about 2.5 inches... will be used for tennis balls (weighted with something or other) and then maybe soda cans later...

they offered to weld the cap and drill the flash hole too... so long as i didn't go around saying that they built me a cannon.

EDIT:  i've been working the end of the pipe and that block with a belt sander, and the pipe is smooth and very flat, but the block is still a little uneven. will this be a problem for getting a proper weld, or will it not have any effect?

thanks for any opinions and advice.
-Jon

PS:  i know that this could result in a weld failure, which i do plan to take precautions for.  this pipe isn't going to break, so if anything does, it'l be the weld.  i will probably have that part below ground level (in a little hole maybe) to catch shrapnel if it does happen to break).. on top of that i'l be taking off from the launch site on a little gas motor scooter that i picked up from a yard sale the other day (this thing is fun!) and getting out of its kill radius.

[GGaskill]

Standard beer/soda (12 oz) cans will not fit in 2.5", they are about 2.6".

How thick is the flat piece?  It needs to be thick enough to not bend from firing.  If it bends, the weld will become highly stressed and it can come off as a projectile.  I have heard of people being killed this way.  If your projectiles are low mass (tennis balls are low mass), there won't be much risk.  Risk increases as the projectile mass increases.

It might be better to make a cylindrical insert with a powder chamber instead of using the flat end piece.  It would lessen the end thrust from the explosion and be be so thick that bending of the end cap would not be a risk.  It would be best to shrink fit it and then weld afterward.  Adding a shrunk-on reinforcing band like a Parrott rifle would add safety.

[Cat Whisperer]

Mortarnoobie -

Cool piece of tubing.  BUT NOT a good design.

(I know you'll deal with the issues of the cannon/mortar of which this will be a replica - to keep it legal - that's another issue.)

Do you know the type of steel?  Very important if it is going to house the explosion directly; less important if you have a powder chamber.  That's the principle that Coehorn employed in the 1700's.  Cast bronze mortars that were light but had BIG bores.

Take advange of it by having a piece of steel turned on a lathe that can be press fit or threaded into the breech.  Have a powder chamber cut into it.  That way the pressure peak occurs inside the powder chamber and you have massive strength around it.  LOOK at the many designs posted here - you will see lots of metal around the powder chamber then thinner walls for the tube where more strength isn't needed.


Caliber - that's the tough one.  I prefer to design around commonly available ammo.

[mortarnoobie]

the steel block is about 3/8 inch thick.  i am going to look at different sizes of pipe they have and try to find one that will slip into my piece to act as the powder chamber, weld that in, and then weld the block on top of that.  i'll talk some more with the older guy that worked there... he sounded like he's had more than enough experience with building and helping build these things.

btw i know it isn't exactly 2.5" i was just giving a general idea

[Cat Whisperer]

The issue is the nature of the weld.

Two things:  a) with a certified welder it IS possible to get the pre-heat right and the cooling right with the right low-hydrogen rods to get a good weld that doesn't have hard spots (susceptable to cracking).
b) there WILL be some porosity that OVER TIME the products of combustion will leach into.  That WILL cause a weak spot which will eventually crack.

ONE solution is to press fit the breech plug deep enough (away from the welded area) AND so designed to SEAL (with crush fit)  the end such that there will be no posibility of corrosion.

Check how the N-SSA requires it to be done.

[mortarnoobie]

modifications to the design were made:  a 1/2" thick wall piece of pipe (approx. 1.5" ID) was slip fitted into the combustion end, welded into place, and then a 3/4" thick plate was welded (like a tank!) on top of this.  The guy who worked with me (been welding since 1964) could not say much more than "that aint goin nowhere" after he was done with it.  He knew what its intended use was, and put it together with said intention in mind (not to mention he has constructed and fired more than a couple similar designs himself, only without a powder chamber like he put on mine, and he has yet to have a mis-hap).  will it last forever?  probably not.  will i fire it with this knowledge and take precautions based on it?  yes.  

i'll post results of various projectiles, most likely starting with the tennis ball (not filled w/weight)

as for legality: firing will take place on a friends private property out of the city limits.

[GGaskill]

Tennis ball diameter (from the rules of tennis):

"In all tests for diameter a ring gauge shall be used consisting of a metal plate, preferably non-corrosive, of a uniform thickness of one-eighth of an inch (.318cm.) in which there are two circular openings 2.575 inches (6.541cm.) and 2.700 inches (6.858cm.) in diameter respectively. The inner surface of the gauge shall have a convex profile with a radius of one-sixteenth of an inch (.159cm.). The ball shall not drop through the smaller opening by its own weight and shall drop through the larger opening by its own weight."

[Cat Whisperer]

.... as for legality: firing will take place on a friends private property out of the city limits.

Probably better than doing urban redevelopment in downtown KC, but read and know the laws on what the configuration should be a replica of, http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=65044&sid=eafbf720c25010801701fa86daf1f37d - ggaskill has said it very plainly.

See also DD's sticky on FAQ's: http://www.graybeardoutdoors.com/phpbb2/viewtopic.php?t=16901 and READ the content (link to BATF) on the law.

You shouldn't have any trouble with tennis balls (other than finding them or burning the fuzz off one side).  When you graduate to heavier projectiles you'll develop MUCH higher pressures - consider very carefully proof testing.

[mortarnoobie]

we will probably stick with tennis balls on this design... the only step up would be to weight them down (not a lot... probably something lighter than cement).

Cat i sent you a PM describing my plans if the weld does fail.  
i'll post it on here for others to see as well.

( private message to Cat )
if the weld does end up failing (i won't be suprised... i don't plan on it happening, but i'm not assuming i have a high quality design... i will be careful.), i think my plan of action would be to locate a solid steel cyinder (2 inches long or so) and have it turned to a snug fit in the pipe, then drill 2 holes (perpendicular about an inch from eachother vertically) through the pipe and cylinder and bolt them together hardcore... no welds to break then, and i would still keep the long barrel that was my original inspiration.

this design would not have a powder chamber (with this grade of pipe; seamless DOM; it is probably not necessary, but maybe it would be good to have just to do it right) unless i got a longer cylinder and had one bored into it.  

(Does this general idea sound good?)

again, this is based on the weld failing (if and when).  I like to give stuff like this a try, and chances are i'll A. lose interest in firing it,  B. enjoy it a lot and make a better design.[/i]

[GGaskill]

You shouldn't be talking about welds failing unless you are doing strictly an experiment to be tested to destruction.  There is about a century of electric welding experience now and there is no excuse for poorly designed weldments or poorly executed ones.

[Cat Whisperer]

a) well overbuilt for tennis balls
b) because of corrosion caused fatigue cracks not good for long-term - must have a good design to seal products of combustion from weld area (same issue of seam vs. seamless tubing).
c) you should be able to achieve low-earth-orbit with a tennis ball - 25' above the ground maybe.

[das]

Hi noobie, hey just want all to know about this!!! Some years back here in Fort Wayne we had a young man build a tennis ball cannon for a shop project. After he put 2 ozs. of 3f in it he started to ram the ball down the barrel with a wood rod when it suddenly went off! The resulting explosion shattered the rod, sent pieces through his hand  and wrist, and he lost most of his hand from it. Investigators said the most likely cause was static electricty from the ball! If that is what you plan to use for ammo, for God's sake, Please be CAREFULL!!!

[Cat Whisperer]

das -

Thanks for posting that.  I'm not sure how many folks here have shot tennis balls before, I haven't.


More philosophy:  a) there are things that you don't do because ONCE-IN-A-WHILE they backfire; and b) you have to be tough if you're stupid.

It sounds like another good reason for putting the charge into a foil package first, then loading the ball, then piercing the foil and inserting the fuse.

[dominick]

Das wrote:

Hi noobie, hey just want all to know about this!!! Some years back here in Fort Wayne we had a young man build a tennis ball cannon for a shop project. After he put 2 ozs. of 3f in it he started to ram the ball down the barrel with a wood rod when it suddenly went off! The resulting explosion shattered the rod, sent pieces through his hand and wrist, and he lost most of his hand from it. Investigators said the most likely cause was static electricty from the ball! If that is what you plan to use for ammo, for God's sake, Please be CAREFULL!!!

Probably would be a good idea to use a safety rammer.  They are easy to make and a lot cheaper than a losing a  hand. Paul Barnett of South Bend Replica Co. advocates  the use of safety rammers for all types of cannons. His catalog has several examples of various rammers. The above incident was from a tennis ball, then one can only imagine what a lead round would do!  YES, Be careful!

[mortarnoobie]

i did some google searching about this safety rammer and can't seem to any info.  could someone fill me in a bit... sounds like a good thing to have.

something that is a bit on my side, however, is that the ball fits loose enough that it won't require ramming... it slides down a reasonably slower than it would at regular gravity, so if i was worried, i could simply set the gun in position, drop the ball in, and be out of the way in case it did occur.

[GGaskill]

A safety rammer looks like a cane, one end bent back over.  You hold it on the part that is not in front of the bore and should you get a premature explosion, the closed part doesn't pass through your hand.

[Cat Whisperer]

i did some google searching about this safety rammer and can't seem to any info.  could someone fill me in a bit... sounds like a good thing to have.....

Good for you!  Sometimes there are different terms that folks use for the same item and you won't often find good links using a search engine.  Another hint, if you're looking for cannon wheels there aren't many cannon wheel manufacturers out there, but there are a few Amish folks that make wagon wheels that come very close.

[mortarnoobie]

based on the rather crude nature/fit n' finish of my gun, i don't think i'll bother with trying to make accurate replica wheels.  i'm thinking something along the lines of a wagon/little kid bike wheels mounted on a carraige of 2x4s with the barrel harnessed in with hose clamps or something.  





compelted barrel... (soda can is for size comparrison.. atleast for now)
it might be a little rough lookin, but atleast its patriotic.

[Cat Whisperer]

Ahhh I recognize the urban cammo.

When I first fired my beer-can caliber mortar I would just fill the can with water.  If there was too much powder it would push the sides of the can out and scrape the sides of the bore.  Sand or cement filled is much better.

Build something for a base.  If it's not right, build it better.

[Double D]

I suggest you cut that barrel down so the the portion that your tennis ball rides in is two calibers long.  That is,  the length of two tennis balls.

First you don't need the length, second the shorter length will look more pre 1988 coehorn mortarish than a longer post 1899 Stokes mortar type tube.

Appearances  are everything and you want to appear to be a youthful historian and not a wild eyed radical studying a fine old Civil war design.   When you get to be older, and balder and fatter and your beard is scraggly and gray/white its easier to be a wild eyed radical when you look like an old historian.

[mortarnoobie]

it does have an unfinished carraige now... its crude enough to be rather  embarrasing  so i will post the pictures when it is done and painted.

it does its job though... the barrel can be sturdily elevated between 15 and 75 degrees.