Advice to a greenhorn?

[GTS225]

Yep.....FNG here.
Looking for advice on building a SAFE black powder thundermug or small cannon with a golf ball bore.
Have been doing a LOT of reading and searching, have discovered that I'll need a bore of 1.750, not less than 1.740.  Have found that many have used 1018 cold-rolled stock for thier tube.  Have also learned that I need not less than a bore's dimension of material surrounding the powder chamber.  (Questions on this later.)
Have obtained a 4" by 24" piece of steel, but it appears that it's not 1018.  Has a red paint swatch on each end, and what info I can find suggests it's 12L14.  Unable to determine if it might be suitable to spin a barrel out of it.  (Could use a yay or nay on this.)

Now.......addressing the bore's dimension surrounding the powder chamber.  I've seen drawings where the powder chamber was reduced from the barrel's I.D.  Does this suggest that I might be able to make a cannon or thundermug with a 1.75 bore, but with a smaller powder chamber, from my 4" steel stock?  If so, that would give me a tube wall thickness of just 1.125, and that seems marginal to my brain, but I'm not an engineer, and do tend to "over-engineer" whatever I might build.
Okay.....a little further into the simple subtraction shows me that my powder chamber can't be any larger than .500" i.d. in order to preserve the bore's dimension around the powder chamber.  So much for using 4" stock.

Back to the search for a more suitable chunk of steel.  I'll wait for your advise to see if I can still use this 12L14 for smaller bore noisemakers.  I might be able to use it for something like the blunderbus bore gun starting at 4:42 in this video.  --> https://www.youtube.com/watch?v=CkogmqJzXmI

Pardon my rambling.....Roger

[GGaskill]

Take a look at these threads for thunder mug info:

A mascleta to ring in the spring

A Thunder Mug for Zulu

The first one is a 1" bore; the second is a 1.5" bore.  The 1" makes a lot of noise and can be made from 4" material. 

[GTS225]

Thanks for the links, Mr. G.  I like the external appearance of the mug for Zulu, so I may work at scaling it down to the 1" bore.  I do have some 1" thick plate out in the shop that may work for the base the way you did on Zulu's mug.

What I'd really like to try is a piece with the appearance of a chess rook.  The little castle tower with the guard ring around the apex.  Would make a heck of a decorative doorstop, too.

Just brainstorming.....Roger

[GTS225]

Well, shoot!  Back to the material search.  Discovered that the 12L14 is a leaded steel, not suitable for containing explosions.  Guess I'll keep it around for less stressed projects.

Bummed.....Roger

[Double D]

For a golf ball cannon.

A golf ball gun with proper 1/40 windage would need a minimum bore of 1.723 inch.
The diameter of a golf ball is 1.68 inch. .  (1.68/39)x40=1.723. 

You need round stock that provides a one caliber wall thickness over the chamber.  Golf ball bore is 1.723 so you steel needs to be 5.169" inches minimum over the  chamber.

Do not do a reduce chamber.  It is a special chamber and is not  made by just using a drilling a smaller hole.  On cannons it is reduced by being tapered.   It is difficult to load and requires special loading techniques to load safely.

Mortars do use reduced chambers and but their barrels are also shorter and can be easily and safely loaded.

Do not make this cannon up out off you head. 

Get a set of plans, we can help you with that.  Look at the plans and replicate your cannon from that.  The original designs have safety features built in to them.  Copy them and will copy the safety into them.

Thunder Mugs are different beasts all together.  If all you want to do is make noise, then make a thunder mug.  We can help you with design of those also.

[GTS225]

For a golf ball cannon.

A golf ball gun with proper 1/40 windage would need a minimum bore of 1.723 inch.
The diameter of a golf ball is 1.68 inch. .  (1.68/39)x40=1.723. 

You need round stock that provides a one caliber wall thickness over the chamber.  Golf ball bore is 1.723 so you steel needs to be 5.169" inches minimum over the  chamber.

I'm aware of the math.  Was just rounding up a bit in my initial post.  I'm also aware of the safety margin of caliber to wall thickness, as I mentioned in my initial post, as well.  And I'm also aware that I can't just use ANY round stock big enough.  I have a piece of 12L14 large enough for a small cannon barrel, but can't use it because it won't hold up against the pressures.

Do not do a reduce chamber.  It is a special chamber and is not  mad buy just using a drilling a smaller hole.  On cannons it is reduced by being tapered.   It is difficult to load and requires special loading techniques to load safely.

Fair enough.  I hadn't learned that yet, and will do a bit of research on it.

Get a set of plans, we can help you with that.  Look at the plans and replicate your cannon from that.  The original designs have safety features built in to them.  Copy them and will copy the safety into them.

That's happening as we speak, (I hope).  Have ordered a set of drawings from Antique Ordnanace Publishers for a Coehorn Mortar. Intend to scale it down for my purposes.  Also have a couple books on the way.

Thunder Mugs are different beasts all together.  If all you want to do is make noise, then make a thunder mug.  We can help you with design of those also.

This is also something I want to do.  Have an idea to make one with the appearance of a rook.....the chess piece rook.  Would make a good doorstop out in my shop as double duty.

Not to worry about me.  I am quite familiar with firearms, and thier inherent dangers.  I'm doing my best to get this right the first time, without any "close calls".

Roger

[Double D]

Excellent Roger, Excellent.

You will be surprised and pleased with the Antique Ordnance plans.  They are incredible.

12L14 is plenty strong.  It's problem is inclusions and does have a history of failure as gun barrel steel.

The idea of Rook thunder mug is brilliant.

If you were any where near Oklahoma I might be able to help you with you project.  I have a piece of 1018 20" x 5".  You could  probably make a coehorn and thunder mug from it-FOB Edmond OK.  Come get, it is yours

This is from the Guns on Wheels legacy collection.

[GGaskill]

If you can deal with .dwg or .dxf drawing files, I could email you the plan for Zulu's thunder mug and/or a Coehorn mortar.

It's interesting to note that the rook piece is called a "cannon" in a number of languages.  See wikipedia Name Translations.

[GTS225]

Excellent Roger, Excellent.

You will be surprised and pleased with the Antique Ordnance plans.  They are incredible.

Good to hear.  I should be able to follow them quite nicely.

12L14 is plenty strong.  It's problem is inclusions and does have a history of failure as gun barrel steel.

And that's what my research has found, as well.  I figure it's not worth it in the long run.  Somebody is going to inheret this, and I don't want them getting hurt because I did a foolish thing.

The idea of Rook thunder mug is brilliant.

Thanks......just a little bit of imagination in my shoulder-mounted vacuum chamber.  I can't help but wonder what the discharge would look like from above, with that parapet surrounding the muzzle.

If you were any where near Oklahoma I might be able to help you with you project.  I have a piece of 1018 20" x 5".  You could  probably make a coehorn and thunder mug from it-FOB Edmond OK.  Come get, it is yours

Thanks for the offer, but I'm up in northeast Iowa.  That would be an all day drive, one way.

Roger

[GTS225]

If you can deal with .dwg or .dxf drawing files, I could email you the plan for Zulu's thunder mug and/or a Coehorn mortar.

It's interesting to note that the rook piece is called a "cannon" in a number of languages.  See wikipedia Name Translations.

Thanks, GG, but I don't have any CAD software on my magic box, so wouldn't be able to do anything with the files.
The info about the rook translation is interesting.  Just a happy accident, though.

Starting to suffer some "mission creep" with this.  Realized I'm going to need both a taper attachment, and a steady rest for my lathe, so am in work on building both.  Sure is nice having a benchtop mill around for this kind of stuff.

Roger

[GGaskill]

Taper attachments are nice but Zulu's mug was built by aligning the compound rest at the desired taper by trial and error.  Thunder mugs are not high accuracy projects so having the taper a little bit off is not important.

[Double D]

 

If you were any where near Oklahoma I might be able to help you with you project.  I have a piece of 1018 20" x 5".  You could  probably make a coehorn and thunder mug from it-FOB Edmond OK.  Come get, it is yours

Thanks for the offer, but I'm up in northeast Iowa.  That would be an all day drive, one way.

Roger

If you are not in a big hurry and would be willing to meet me along 1-35 some where, Wife and  I drive to Minnesota several times a year.

This would be in character as this steel came out the Gun's On Wheels Legacy. https://www.go2gbo.com/threads/gunsonwheels-legacy-cache.252902/

This was a the cannon collection and building material of a former member that I picked up in Cody WY. Read the linked post to to see what was involved.  We shipped some of the smaller stuff across the country.  The wife and i were still traveling a lot and we would carry parts pieces all over the place and drop them off.  Every time I think I have got rid of every thing, I find something else.  I have the piec of 1018 and some acme threaded rods still left.

If you want this round, and are willing to meet me along I-35, its yours.  I think after the first of the year the wife and I may be headed north to see the great Grandson.

[GTS225]

If you are not in a big hurry and would be willing to meet me along 1-35 some where, Wife and  I drive to Minnesota several times a year.

This would be in character as this steel came out the Gun's On Wheels Legacy. https://www.go2gbo.com/threads/gunsonwheels-legacy-cache.252902/

If you want this round, and are willing to meet me along I-35, its yours.  I think after the first of the year the wife and I may be headed north to see the great Grandson.

Now, THAT is a heck of a generous offer, and one I'm more than willing to accomodate.  Shoot, I'll even toss a C-note your way to help with the fuel bill.  You just let me know when, and I'll head over.
There's a truck stop about ten miles south of the highway 20 exit that would be quite convenient for this exchange.

And I read that thread.  You did one heck of a service for quite a number of folks.  You get an "atta-boy" for that.

Roger

[GTS225]

Taper attachments are nice but Zulu's mug was built by aligning the compound rest at the desired taper by trial and error.  Thunder mugs are not high accuracy projects so having the taper a little bit off is not important.

I have given that some thought, too.  It's a bit of a short throw, but do-able. Just need to maintain the angle....it's the Y axis depth of cut that needs to be watched. And you're right......accuracy to .001" isn't really that critical for something like this. 
Still, I'll keep building the attachments, as I'm sure they'll come in quite handy for other projects, expecially if I do a longer tube than a mortar or mug.
Hmmmm......I think some kind of angle-to-inches of taper table might come in handy here.  Time to exercise the Pythagorean calculations.

Roger

[GGaskill]

Thanks, GG, but I don't have any CAD software on my magic box, so wouldn't be able to do anything with the files.

I can email a copy of some basic CAD software if you like.  It works well in Windows 7, not so well in W10.  There would be a learning curve to be able to use it.

[GTS225]

It works well in Windows 7, not so well in W10.  There would be a learning curve to be able to use it.

Unfortunately, W10 is what I'm running since my last desktop took a dive.  And both my lathe and mini mill are all manual, so I am quite limited, except for printing the finished drawing out.  I may be better off looking for a 10-friendly version of software.

Thanks just the same.....Roger

[Double D]

Now, THAT is a heck of a generous offer, and one I'm more than willing to accomodate.  Shoot, I'll even toss a C-note your way to help with the fuel bill.  You just let me know when, and I'll head over.
There's a truck stop about ten miles south of the highway 20 exit that would be quite convenient for this exchange.

And I read that thread.  You did one heck of a service for quite a number of folks.  You get an "atta-boy" for that.

Roger

Probably after the first of the year, the wife says---weather being a big issue.

[ulav8r]

NanoCad V5.9 runs on Windows 10 and is free.  https://nanocad.com/products/nanocad-free/

[GTS225]

Probably after the first of the year, the wife says---weather being a big issue.

Understood.

Roger

[GTS225]

NanoCad V5.9 runs on Windows 10 and is free.  https://nanocad.com/products/nanocad-free/

Thanks......bookmarked for the moment, and I'll check it out.

Roger

[GTS225]

You will be surprised and pleased with the Antique Ordnance plans.  They are incredible.

You, sir, were quite right about those.  Got them yesterday, and they'll be a great referance source for my build.
I did notice that, if one builds to exact scale, it seems that wall thickness doesn't follow the bore thickness rule.  I suspect that it's due to "unknowns" back when they originally built these from cast iron.
In any case, I'll maintain a generous margin of safety.

Roger

[Double D]

In a mortar the the critical wall thickness measurement is over the powder chamber.

 The  Coehorn chamber is tapered 3 inch at mouth by 2 inch at base,  The mouth of the chamber has walls 2.825 thick.  The majority of the chamber as it tapers back to base 2 inch diameter has 2.5 inch walls.   Tapered chamber and smaller charges made this a safe design and a proven design.

Moderns safety recommendations  of the North South Skirmish Association require the one caliber wall thickness in all new made and relined or repaired.

If I were making a mortar from the AOP plans, I would simply reduce the dimensions of the chamber to give me the N-SSA suggested wall thickness.  The difference will not be readily discernable visually orwhen shooting.  You gun will have that extra margin of safety.

[GTS225]

DOH!  Missed the dimensions on that.  I did notice the smaller powder chamber, though.  And remembering my hydraulics learnings, pressure drops dramatically when it enters a larger area.  I was looking at just the barrel wall thickness initially, until you jogged my dormant memory cells.

Navy aviation school drummed it into our heads, "attention to detail".  Gotta remember that.

Roger

[Double D]

Great  Grandson's 2nd birthday is in March in Minnesota.

Wife says we should attend the party.

[GTS225]

That works for me.
There's a Love's Travel Stop at the Ellsworth/175 exit that will work for this. 
(Sorry. don't know the exit number.)
We'll work out the time window as it gets closer.

Roger

[GTS225]

Quick question;  How does one contend with dimensional descrepancies when trying to build to scale?  If I follow the scaling math, I end up with thin walls around the chamber.  If I follow the wall thickness rule (chamber wall=bore), then external dimensions aren't to scale.

Stick to chamber wall=bore rule and work around that?

Thanks.....Roger

[Double D]

Use the scale dimensions for exterior.  Measure the OD over the chamber and divide  by three.  That is the bore diameter.

If bore is critical then multiply by three and that becomes the diameter over the chamber.  Scale to  that dimension

[GTS225]

Got it.  For a set bore diameter, wall thickness first, outer appearance secondary.

Thanks.....Roger

[Double D]

No, for a specific bore diameter,  scale up to give to get the wall diameter and use that scale for the exterior dimensions also.

 

[GTS225]

But I'm scaling down to get a golf ball bore.  It sounds like we're mis-understanding each other.  I think you're trying to tell me to set my bore, add the safe wall thickness around the chamber, then scale the exterior to that safety factor.

OK....just re-read your last.  I follow it now.  I'll actually have two "scales".  One for the bore and chamber, and a different scale for the exterior.

Roger