The Craftmans Shop => Backyard Ballistics => Topic started by: BronxFigs on June 30, 2014, 03:58:50 PM

Title: Black Powder Cannon
Post by: BronxFigs on June 30, 2014, 03:58:50 PM
I want to turn some small, Black Powder cannon barrels from scrap steel.  I want to use solid steel roundstock for the barrels to eliminate boring for the liners.  The bores will range from 0.500" - 1.250" diameter.  Barrel OAL between 12" - 20".  These will NOT be competition tubes, and they will be used for firing occasional, salutes (blanks). 

1.   What kind of steel is recommended for black powder barrels.  I can find suitable diameter bar-stock at local scrap yards, and at the local Iron Works which fabricates  iron fence, structural steel weldments, etc.)...but I have no idea what alloys to purchase.  I'm sure the Iron Works will be able to identify the steel roundstock that they are selling....but steel bought at the scrap yards...who knows what it is.  Can I take the chance and use unidentified steel for making a cannon barrel?  Aren't the steels of today - whatever the alloy - strong enough to withstand non-abusive, blank-loads?  (Loads between 70-200 grains of Black Powder).

2.   How do I drill a deep hole down the center of the solid steel rod?  I can buy extra long drills but will that give me a reasonably centered hole down the barrel?  Or, will the drill bit wander off center?  Do/Should I bore a hole first, and then, go in with a drill bit to the required depth?  Step drill?

I will be using a large 14" swing lathe, and I also have use of a drill press,and  milling machine.  Trunninons will be welded into the sides of the barrel.

I am familiar with the shooting and loading of black powder firearms and cannons.  Under the loading parameters that were I have to "proof" these barrels?  If yes, how much of a percentage of an overload charge is enough to proof the barrels...200%....300%...?

Any suggestions?

Title: Re: Black Powder Cannon
Post by: Jonny on July 03, 2014, 03:55:20 PM
Birmingham Proof House has a cannon outside in the yard and will be worth a call. Law to themselves.

I would check in to the legislation, ownership and whether it could be added to your cert whether blank fire or not, it could still fire ball.

The shockwave off a 10guage blank in the 3 Remingtons used to start the IOW boat race is almost enough to blow windows out.
If you know or can work out the operating pressure you initially could test yourself with an hydraulic hand pump and guage for as little as 74.

Title: Re: Black Powder Cannon
Post by: Arbalist on July 03, 2014, 05:48:21 PM
In the UK you'd need a licence but doubt Frank would need one in the US would he?
Title: Re: Black Powder Cannon
Post by: BronxFigs on July 04, 2014, 09:16:22 AM
Thank you for the interest. 


Title: Re: Black Powder Cannon
Post by: Arbalist on July 04, 2014, 09:27:43 AM
Frank, I would have thought even today's mild steel would be stronger than most of the materials used in bygone ordnance. If you stick to the same proportions (OD/bore etc) used for old canon then I would have thought that would be fine for firing blanks. Would be keen to see what you come up with in any case! Good luck with the project.

PS. I've always liked the look of the old Dalhgren's used in the civil war ironclads.
Title: Re: Black Powder Cannon
Post by: Lew_Merrick_PE on July 04, 2014, 12:59:21 PM
Frank (& All),

1) Here in the U.S. the laws vary all over the place.  In certain States (California, Massachusetts, & New York I believe) you cannot own such a device personally.  In other States, you have to register it with your local police or sheriff's department.  In other States, you have no restrictions at all.  I am not conversant with the specifics of these regulations.

2) Black Powder is a deflagerant which means that it builds pressure more slowly than other propellants.  The issue is how much gas and what pressure & temperature results from igniting it.  This is usually published as 100 cm bomb pressure & temperature data.  (Understand that in pyrotechnical terms a bomb holds and prevents the release of energy of combustion.  It is a bombast that actually bursts to release such energy.)  The absolute pressure & temperature is the energy released by combusting the propellant.  The values you get from a 100 cm bomb will be for a specific (and small) amount of propellant.  Be sure to read the entire document to find out how to expand such values to your load!

3) The resistance to energy is the area under the curve of a stress-strain diagram.  You will want to have enough material to absorb the propellant's energy with a factor of safety that is no less than 3 to the yield point's energy.  Thus, for A36 (common structural) steel, you will typically have an area under the curve of (36,000 lb/in X 36,000 lb/in / 13,500,000 lb/in/in =) 96 in-lb/in.  This is highly simplified as there are geometry effects involved, but this is one aspect you need to account.

4) The maximum pressure pulse is another.  For a thick-walled tube (i.e. a cannon barrel), the shear stress = Pressure X (Ro + Ri)/(Ro - Ri).  Where Ro is the Outer Radius & Ri is the Inner Radius.  The allowable shear stress for most steels may be approximated as 0.63 X Ultimate Tensile Strength and should have a factor of safety applied that is no less than 7.

5) Also based on the maximum pressure pulse is the hoop stress engendered.  This is tensile stress = (Pressure X Ro)/Radial Thickness.  For A36 steel, the allowable tensile yield strength is 36,000 lb/in.  A factor of safety of no less than 3 should be applied to this.

6) And then their is the dissipation of retained heat which will determine your maximum rate of fire.  It is fairly easy to raise the temperature of the barrel into the 600F range which will reduce all your allowable stress & allowable energy values by anywhere from 30% to 70% depending on the material.  This was the most common cause of early cannon failure!

All I have done here is to give you a very general overview of the problems you will face in making such a device.  My background in this arena has more to do with insertion & removal of rounds, stripping said rounds from magazine presentation, and the mechanics of boring and rifling barrels for such devices.  The equations I have cited for energy, shear, & tensile stress are readily available (Machinery's Handbook is one reference for them, just about any engineering stress analysis text will give you more detail on them).  Be very careful if you decide to proceed!  One failed barrel can ruin a lifetime...
Title: Re: Black Powder Cannon
Post by: BronxFigs on July 12, 2014, 09:08:21 AM
Lew Merrick, and others....thank you for your interest and for the suggestions.  I will definitely take all comments under consideration.

Years ago, while still in my Salad Days, I used to shoot a .50 caliber Hawkins rifle and loaded it with about 120 grains of Pyrodex.  I think the hex. barrel was about 1.00" across the flats.  I don't think the cannon that I plan to make will have a bore larger than .750" diameter, and the breech section, from the trunnions back to the cascabel,  will be at least 3.00" - 3.50" diameter.  I think the barrel will be similar to the old Wiard rifled cannon....basically.

I'm guessing that this heavy breech section will have enough strength to contain the pressure of 120-150 grains of Pyrodex.  The OAL of the barrel will be roughly 13".  I'll still proof the barrel before firing the occasional salute.  I think any commonly found steels will work well for this purpose.


Title: Re: Black Powder Cannon
Post by: BronxFigs on July 13, 2014, 10:22:25 AM
Yep.  I decided that my short attention span will tolerate turning a Wiard-style cannon barrel.  Just basically a two diameter barrel.  Larger diameter section from trunnions back to breech, and a smaller diameter section from trunnions to muzzle.  Neat, clean lines, easy job....done.

So, I'll chuck full-diameter bar-stock, cut to length, center-drill, then deep-hole drill,  then ream/finish the 0.750" bore.
Unchuck work.  Bore two recessed holes for trunnions on milling machine.
Re-chuck work, and finish turning outside profile of barrel.  OAL: 13"  Chase to breech section; 3.00" dia.  Chase to muzzle approx. 2.00" dia.
Turn and mount trunnions (Braze/Silver Solder).
Proof load.  Light the fuse.  If all is OK, start making some noise.

Thanks for the interest, and all the suggestions.

Title: Re: Black Powder Cannon
Post by: Arbalist on July 13, 2014, 12:44:04 PM
Let's see some pictures when it's done Frank!

I've thought about making a Canon as well but thought about making it from larger stock so that the trunnions are part of the barrel, not additions. I understand in bygone days they used a "trunnion" Lathe to achieve this but I could not find any details of how this was actually done.
Title: Re: Black Powder Cannon
Post by: BronxFigs on July 14, 2014, 07:20:28 AM

Thanks for the interest.  I will take some photos of the barrel-making process and capture my screw-ups, failures, and triumphs.  But then, I will need help with how to post them.  Computers and me don't mix.

Trunnion Lathes, etc.
I don't know how large a diameter barrel that you are going to machine, but  (I'm speculating), making a barrel with intergral trunnions will require an incredible amount of machining, and stock removal.  Also, how will you machine the band of remaining metal from between the trunnions?  You could turn the profile of the barrel from muzzle to breech, except for the area surrounding the trunnions, which will still be at full diameter across the trunnions.  Even if you found a way to machine the trunnions (milling machine, w/boring head, etc.), and remove the band of extra metal, you will still need to hand file and then finish the area around the rimbase of the trunnions, to blend them into the curved and tapered, barrel.  (I'm envisioning a traditional cannon, i.e. a barrel that is tapered from breech to muzzle).

I suppose you could remove that problematic, band of extra metal from between the trunnions, by doing some kind of a set-up in a milling machine so that the barrel could be slowly rotated under a cutter, and by degrees cutting away the metal to match the taper at that section of the barrel.  You might even be able to machine away that band by using the lathe carriage and a cutting tool, as a "shaper", while the barrel is mounted, and rotated while still chucked in the lathe.  I'm no machinist, so maybe others will come up with alternative, and more efficient ways to machine away all this extra metal.  My guess would be that the whole process is quite a huge p.i.t.a.  One bad cut, and oops!

Honestly, I don't think there is any "easy" way to machine integral trunnions.  Most modern reproduction cannons made from bar-stock, have trunnions welded onto the tubes....unless of course, the finished cannon barrel started as a casting.

Judging from the old engravings that I've seen, I believe that "trunnion lathes" were mounted at 90 degrees to the length of the barrel and came in with some kind of cutting tools to machine  the circumference of the trunnions while the barrel was still mounted in the lathe....but the extra metal must still be machined from between the trunnions.  But how?  I have no clue.

Go for it...  Make a barrel.  We only live once.


EDIT:  Go to: "Seacoast Artillery" for photo of a cannon barrel being machined in the area of the trunnions.
Title: Re: Black Powder Cannon
Post by: bertie_bassett on July 14, 2014, 03:46:07 PM
i have a feeling that cannons with integral trunnions didnt have much of the exterior actually machined, they were cast with the  taper and with the trunnions in place.  The external machining would just be truing up the trunions themselves and cleaning up each end of the barrel. The rest of the machining is just boring out the center.

i could be wrong with this though, but most old cannons iv seen have an 'as cast' exterior. i think ?
Title: Re: Black Powder Cannon
Post by: Arbalist on July 14, 2014, 05:02:00 PM
I think you're right Bertie.
Title: Re: Black Powder Cannon
Post by: tom osselton on July 14, 2014, 05:55:33 PM
I don't know Figs and cannons should not mix!

 Although I have heared "  I don't give a flying Figg! !!!
Title: Re: Black Powder Cannon
Post by: BronxFigs on July 15, 2014, 06:56:28 AM

In your posting #8, you  stated that you'd like to make a cannon using larger stock so that the trunnions would be part of the barrel.  Your wording made me think that you are going to machine a barrel from bar-stock.  If you are going to cast a cannon barrel, you will have no problems, however if you are going to turn a cannon barrel with integral trunnions, then you will have a trunnion ring to deal with, and, machine away.

My understanding is that as cast trunnions were just cleaned up a little ...if a trunnion lathe was not available.

Either way you choose to make a barrel you will have fun.  Good luck.

Title: Re: Black Powder Cannon
Post by: Arbalist on July 15, 2014, 08:37:54 AM
I had a look at the site suggested, very helpful.

It's on a long to-do-list when my workshop is set up.  :D
Title: Re: Black Powder Cannon
Post by: bertie_bassett on July 15, 2014, 04:44:42 PM
That looks a very long job making it from solid bar. And a lot of wastage.

cnc would probably do a good job of milling away the trunion ring complelty, and in sure with the right tools and a huge amount of time it could even be done manually. Would certainly be an accomplishment to make it from on big lump
Title: Re: Black Powder Cannon
Post by: Arbalist on July 15, 2014, 04:53:06 PM
Agreed, but it must be the strongest way of making a cannon barrel, especially if it's a high grade steel.
Title: Re: Black Powder Cannon
Post by: BronxFigs on July 16, 2014, 01:50:27 PM
I need your experienced opinions....

Let's say that I will turn a barrel from solid steel, and either silver-solder, or weld the trunnions onto the barrel.  The full diameter of the barrel where the trunnions will be welded is 3.00". 

My question is:

Should I do all the work on the trunnions, i.e. welding, etc.  BEFORE drilling and reaming the barrel bore?  I'm thinking that if I first drill and ream the bore and then apply a welding torch, etc... is it possible for the localized heat to warp the barrel, and thus, have a warped bore as a result?

Also...does it matter if I machine a barrel using either hot-rolled or cold-rolled steel?  Are there any real differences in this particular application?  Are there warping stresses involved with machining these steels?  Could I use either, one or the other?

Comments and suggestions are wanted.

Title: Re: Black Powder Cannon
Post by: Jonny on August 02, 2014, 03:57:58 PM
I would drill and finish the bore before turning o/d.

Trunions the easy bit unless 5 axis in bulk but then have to set and proggy the thing for one part. Far easier and quicker manually, i do things like that daily that cnc ers refuse to do, well they just want easy work - too much hassle.
Far easier bore through to dia required, make a jig to suit bore and horizontal rotary table jobby, spigot either before, during or after.

Title: Re: Black Powder Cannon
Post by: Eugene on August 10, 2014, 05:18:33 AM
Here is a link to a site that shows the making of a full size punt gun. The processes would easily scale down for your purposes. (

The simplest way to attach trunnions which avoids any chance of compromising the barrel metallurgy is to enter/ weld them into a collar and shrink fit the collar to the gun. I've seen a lot of punt guns done that way.


In the gun above the entire breech section complete with trunnions welded in is shrunk on very neatly and successfully.


Title: Re: Black Powder Cannon
Post by: awemawson on August 10, 2014, 05:22:54 AM
load with too much powder on that thing and you'll go backwards  :scratch:
Title: Re: Black Powder Cannon
Post by: Eugene on August 10, 2014, 05:58:59 AM

A little bit of recoil is taken up in the stretching of the breeching ropes, but the great majority does just as you suggest; send the punt backwards. Obviously there are lots of variables but the principle of every reaction having an equal and opposite reaction is well presented in gun recoil. I've seen punts go back four feet with a good load up he spout; Isaac Newton is alive and well living somewhere on the Medway.

The entire thread runs to 50 web forum pages, but it's both fascinating and inspiring. Terrific design skills and craftsmanship together with a very understanding 'Er Indraws.

Title: Re: Black Powder Cannon
Post by: BronxFigs on August 10, 2014, 07:56:09 PM
Thank you for the interest.

Gathering material, bar-stock, tooling, etc. for the project.  I decided to turn a "mock" barrel from wood, just to check carriage proportions, barrel dimensions, etc.