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Designing Swivel Gun

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Brad Foust

36 Cal.
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I have a piece of 3" Dia steel and plan on building a swivel gun. I have a friend who will drill the bore to what ever dia and depth I need.
So, how large a dia bore can I safely put in a 3" outside dia breech?
I would like 1-1/4" or 1-3/8". I dont think I dare 1-1/2"??
I will not overload it, maybe 100 gr FFG to 150 Gr FFG Max. But I cant control what anyone else might do later, so I want to keep it safe.
Surly, there is some kind of "Ratio" guide line of Bore size to wall thickness for steel?
Any help would be appreciated. I dont want to end up in the Catastophic Failure section!
Thanks in advance.
Brad
 
The rule of thumb ratio is one caliber wall thickness over chamber--- 3 inch OD = 1 inch bores but You also need to use the right kind of steel. Recommended is 1018.
 
Well, I have alittle more information, ideas.
The steel I have is 1045 which suposedly gives 82KSI (82,000 KSI ?)
Also, I spoke with a blackpowder rifle barrel builder, who thinks I am plenty safe a 1-1/4" Bore or even more.
Consider a 50 cal rifle is often built on a 7/8" oct barrel. A 54 cal on a 15/16" and a 58cal on a 1" oct barrel. Of course I realize there is added strength due to the additional stell acrocc the octogon. These are all over half.
But also, what is the outside diameter of a 75 cal brown bess barrel?
I have a 20GA / 62cal folwler that the OD is 1-1/16". That leaves a wall thickness of
(1.0625 - 0.62 = .445 devided by two = .22125")
Thats less than 1/4". And I would never go that thin.
Man thats thin!! Am I doing something wrong with my math?
I have a couple old military muskets here and I am going to check them.
In the mean time, I welcome your thoughts?
Thanks,
Brad
 
Bigmon said:
Well, I have alittle more information, ideas.
The steel I have is 1045 which suposedly gives 82KSI (82,000 KSI ?)00

Check on weldablility. That 45 number indicates high carbon and requires special heat treat and anneal process to weld. That's why I said 1018. You can weld the trunnions in place.


That is why
Also, I spoke with a blackpowder rifle barrel builder, who thinks I am plenty safe a 1-1/4" Bore or even more.



Consider a 50 cal rifle is often built on a 7/8" oct barrel. A 54 cal on a 15/16" and a 58cal on a 1" oct barrel. Of course I realize there is added strength due to the additional stell acrocc the octogon. These are all over half.
But also, what is the outside diameter of a 75 cal brown bess barrel?
I have a 20GA / 62cal folwler that the OD is 1-1/16". That leaves a wall thickness of
(1.0625 - 0.62 = .445 devided by two = .22125")
Thats less than 1/4". And I would never go that thin.
Man thats thin!! Am I doing something wrong with my math?
I have a couple old military muskets here and I am going to check them.
In the mean time, I welcome your thoughts?
Thanks,
Brad

None and I mean none of those barrel are cannons. That rifle barrel maker doesn't make cannons does he? Cannons are completely different animals.

Now ask you self why is it that both the American Artillery Association and the North South Skirmish Association, modern muzzle loading cannon shooting organizations as well as Robert Muller in his treatise of Artillery 1780 all call for a one caliber wall thickness over the chamber.

And why would you want to ignore such safety guidelines

You did ask for the ratio.

Have you given any thought as to what you are going to shoot in your cannon. How much windage are planning on? Lead is okay for one inch but over that in bores this big it's not that great. Builds to much pressure, excessive recoil is rough on carriages, and larger heavier shot are to easily deformed in handling.

For that matter have you given any thought as to what pattern gun you are going to replicate.
 
Great info, thanks for the input!
This is why I am asking for all your ideas and knowledge. This must be safe.
I am also confering with filks on "Jouster.com", on the black powder forum.
I am getting very similiar info and advice.
Except for one important part.
There, they are reccomending 1080 steel. Here 1080 is being discouraged.
Regarding rifles and cannons being soooo different. I can except that they are different. But why sooo different. What is the big differance that a rifle can exceed 50% of wall thickness, and a shotgun even more.
But a cannon must not exceed one third??
This is getting very interesting. I really appreciate all the input.
Thanks
 
Bigmon,

I suggest you look up "hoop stress" on line and read about the differences in "thin wall" and "thick wall" cylindrical pressure vessels. Stresses are very different as the inside diameter of a pressure vessel increases and as the ratio of wall thickness to diameter changes. Also, you need to look at both the "yield" strength of a material and the "ultimate" strength. The 82ksi (82,000 psi) is what...ultimate or yield ? The problem is fairly complicated if you do a complete engineering analysis.

The rule of thumb that the bore be no more than one third the diameter of the breech was established over centuries of artillery manufacture and is a good rule to live by even with improved modern materials. If you really need a bigger bore, getting a larger piece of material would be prudent and certainly a lot cheaper than a trip to the hospital or morgue.
 
First 1080. 1080 has high carbon content and requires special welding techniques in order to avoid embrittlement issues around the welds. Same problem with 4140 type steels. Both steels are very good steels for ordnance use as long as you have the special skills required for the welding.


1018 has all the right characteristics needed plus it lower carbon make it easier to weld. It is just easier to work with.

With 1080 and 4140 you could have lighter thinner barrel, but why would you want it? Lighter thinner barrels won't dampen recoil very.


The One caliber rule is a safety rule for shooting the AAA and N-SSA, and just happens to be what the Muzzle loading artillerist used of old used as criteria for safe construction.

I don't know how many times over the years I have had this discussion and never under stood why anyone would want to ignore a safety rule.

Get your self a set of cannon plans. Scale it to your steel and build a cannon. Use 1/3 of the diameter over the breech as the bore diameter.

If you do this you will end up with a gun that you can be proud of and not a silly looking skinny piece manure that only takes one one look for everyone to know you haven't got a clue what you are doing.

Here is my 1 inch bore gun.

standard.jpg


standard.jpg


click on picture.

Is this badas enough for you?
 
That is a nice gun. Did you build it?
I would like to build a Swivel Gun like was used on the early frontier here in Pennsylvania during the F&I days.
That stle, say abarrel about 18" - 20" with a wooden tiller, on a yoke. Not a miiature replica, but more full sized.
I am not ignoring the ratio rule. I am more like investigating the why?
I have pretty much came to the conclusion that increasing the bore by 1/4" or 3/8" or so, is really not worth the risk, for what little is gained vs the risk.
No risk is acceptable. I would never enjoy the gun if I always had doubt in the back of my brain. And maybe to be displaced by a big chunk of steel in the back of my brain.
I think I can live with the 1" bore and gain the larger bore appearance by simply opening up the muzzle some to make it a funnel look.
I appreciate everyones input.
Thanks, keep your powder dry.
Brad
 
cannons and rifle are not the same
Here is one alternitive tot he problem as i see it as your steel is not realy safe to go above 1" bore size safely
i may suggest you search the howitzer design withe powder chamber to give you the safe protection at the breech and then you can go with a bigger bore
1018 steel flexs when it is shot and this help with stress issues
 
I built that gun 30 years ago.

So what did a swivel gun look like?

Why would you want to flare the muzzle?
 
That is a nice gun. It doesn't look 30 yeaars old.
A swivel gun is called that because it swivels left and right and up and fown easily on a "yoke".
It has a "tiller" that attaches at the cascable ball on the back that the shooter holds to aim the piece while touching it off with a torch held in the other hand.
Some old time ships also had these mounted on the railings around the ship and the called them rail guns.
They basically look just like a small cannon barrel being around 18" to 24" long plus the tiller.
It has trunions just like an old time looking Pirate type cannon that the yoke fit on.
The yoke would then be put in a hole in the railing, or a stockade wall or stump or log, whatever was available.
They were used allot on the early fromtier here in Pennsylvania cause they wer lighter and could be transported on a pack horse or mule.
Just pucture a small cannon and you got it.
They did not fire solid single projectiles, but large shot, double "OO", nails, glass, stones,
Anything anto personnel.
Not big heavy cannon loads, but maybe 150 gr at most.
In this way instead of a miniature it will be full sized, accurate representation of what we really had.
I shoot blackpowder F&I era and the swivel gun will fit right in.
As for "funneling" or coning the barrel. That was done like in a blunderbuss to ease loading.
Thanks for your input and interest.
Brad Foust
 
I am fully aware of what a swivel gun is and what they looked like, I just wasn't sure you did.

Anecdotally you do seem to know what they are. But I think if you do some serious research before you build and learn more about them, you can come up with one that looks and acts like a real swivel gun and not a bubba shade-tree concoction; something to be proud of.

The gun in my pictures could very easily be made into a swivel gun by the addition of a yoke.

Get your self a copy of Building 18th Century Naval Artillery for building a real swivel gun.

Whats cool about swivels is they can be pulled out of the yoke and put in a regular carriage.
 
I must have misunderstood you. Sorry. I thought you must not have been familiar with swivel guns by the way I read your message.
Anyway, thanks for the info on the book.
BF
 
Alden how was there prices and quality?? i know they sell lots of indian made guns that are average and decent shooters for a decent price
 
Alden how was there prices and quality?? i know they sell lots of indian made guns that are average and decent shooters for a decent price
 
here are a couple of pics of a swivel gun that I made from 3" shafting years ago 26" overall 18" deep bore by 1" it's not a copy of anything just built it on a whim,
myswivelgun.jpg

JSML_Rende_Pics_041600x450.jpg


the second pic was shooting 300gr 2ff under a 15/16th lead roundball
 
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