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PostPosted: Sun Feb 10, 2019 4:48 pm 
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I have been contacted by a cannon barrel foundry. They want a wood pattern for a Verbruggen barrel so they can cast them.
The pattern has to be in two halves.

So it has to be turned as one unit then split apart at the center laminating line.
For the moment, forget the trunnions.

How do I hold these two halves together while they are on the lathe?
The two halves will be about 43" long.
The rough stock will be 7.5" X 7.5" before it is round.
It will probably be pine.

I'm a little worried about the initial weight. My lathe is a big one. It will handle the length.

Here are some pictures of what I am going to attempt.
Forget the trunnions at the moment.

Here are two halves. I could make the yellow part a little longer and put a screw in there.
Could also do the same at the rear of the barrel.

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Each half will be drilled for removable pegs.

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Two halves put together.

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Setting a half into the casting sand.

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I have to figure out how to keep this thing from coming apart at 2250 RPM's

My lathe

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Zulu

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PostPosted: Sun Feb 10, 2019 5:41 pm 
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Some more pictures of the process. These are of several different types of cannons but you will get the idea.
Zulu

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Impression in the sand.

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The liner set in place.

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I have no idea what's going on here.

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PostPosted: Mon Feb 11, 2019 8:37 am 
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Said 2250 is a tad fast to turn IMHO in the roughing stage, granted OK once balanced out & in sanding stage. To mount halves together, make sure they match together with precision .... apply Titebond 111 to surfaces ...... insert newspaper between halves then clamp for 24 hrs. No need for any other fasteners but if you wish hose clamp either end & or move a single clamp away from tool area. Once finished it will split on newspaper joint, card scrapper, sand if desired.


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PostPosted: Mon Feb 11, 2019 10:32 am 
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Thanks,
I've done some internet searching. Some say use a single sheet of brown paper bag. Others say never use brown paper bag.
Some say use a single sheet of newspaper.
Others say use wax paper.

This is going to be big and time consuming. I sure don't want it flying off the lathe or getting messed up when I try to separate it.

Zulu

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PostPosted: Mon Feb 11, 2019 3:54 pm 
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Hey Zulu,

I second the suggestion to use the newspaper joint. I have used it many times myself. Only a single sheet of newspaper is needed.

Cheers,
Tom

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PostPosted: Tue Feb 12, 2019 8:32 am 
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I have spoken with the cannon foundry.

When the two halves go on to the lathe, the 1" wooden pegs must be in place. They will not be glued.
Note the peg holes in the picture.
They will use pegs to line up the halves when they put them in the casting sand.

They said the halves should not be glued but screwed or bolted instead.

In the past, they drilled and countersunk through both halves and bolted the two together with 1/4" all
thread. Of coarse, the countersinks were deep enough to miss the nuts when turning.

After turning, the holes are plugged with proper size dowels and sanded smooth.

This sounds like the way to go for me.
It could be pretty difficult to separate the two glued halves with the pegs in place.

Plus, there's no chance of the two halves separating while turning with the bolts in place.

Stay tuned, I'll post some pictures of the process.

Zulu

Image

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PostPosted: Sat Feb 16, 2019 8:34 am 
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Well,
I have started the attempt with the wood turning.
I countersunk 3" deck screws to hold the two pieces together and glued end caps on to help.
One end cap I made small enough to fit in a four jaw chuck.

It worked pretty well.

I started out at 350 RPM and it nearly beat me to death rounding it out but it worked.
I have no clue what I was thinking when I said I would start it out at 2250 RPM.

I might not have survived!!!

After rounding, I was able to increase the speed to 750 RPM's and later, after the thing started to take shape, increased to 1200 RPM's.

That is working well.
This is the biggest thing I have ever put on my lathe. It is 44 1/2" long and weighs 53 lbs. in it's unturned state.

I currently have it roughed out and it is ready for fine tuning.
I just hope when it is finished and I pull it apart, both halves remain flat.

Here are some pictures.
Zulu

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PostPosted: Sat Feb 16, 2019 9:14 am 
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Wow! This is sooooo cool. Glad you got it figured out. Thanks for posting this. :-D :-D

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PostPosted: Sat Feb 16, 2019 6:12 pm 
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More pics.

I got stage one finished. I'm happy.
It worked out and both halves are flat.

Now I have to figure out the trunnion issue. They will be 2 1/4" diameter, but they will be mounted below center line as opposed to centered in the barrel. I have to work that out.
They will be poured in the vertical position so they each have to have a 1 degree taper to allow the casting sand to release them without collapsing the sand.
That part is easy. The below center line boring of a 2 1/4" hole is harder.
I'm thinking on it.
Enjoy the pics.

Zulu


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PostPosted: Sat Feb 16, 2019 10:48 pm 
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Cut a block that's curved on one side to fit the curve of the barrel, and flat on the opposite side, such that it will act as a guide at the proper angle for the bit. That way you get a flat surface to start the hole and the drill will proceed into the barrel at the proper angle to the barrel curvature. Does that make sense to you? :)

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PostPosted: Sun Feb 17, 2019 10:44 am 
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That is one option Gene.
The trunnion pocket hole has to be 2 1/4" diameter. It only has to go in deep enough to accept glue.

I could probably use a Forstner bit. It would be like drilling straight down into a hillside.
One side would start to cut long before the downhill side started.

I'm thinking a Forstner bit might do it.

My other option is to take the halves to a friend's house. He has a CNC woodcarving machine and says he could cut the pockets.

I just don't want to mess up the barrel halves. :( They were too much work.
Zulu

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PostPosted: Sun Feb 17, 2019 2:52 pm 
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Zulu wrote:
That is one option Gene.
The trunnion pocket hole has to be 2 1/4" diameter. It only has to go in deep enough to accept glue.

I could probably use a Forstner bit. It would be like drilling straight down into a hillside.
One side would start to cut long before the downhill side started.

I'm thinking a Forstner bit might do it.

My other option is to take the halves to a friend's house. He has a CNC woodcarving machine and says he could cut the pockets.

I just don't want to mess up the barrel halves. :( They were too much work.
Zulu


I'd assumed you were thinking Forstner, which is where the guide block would come in, but the CNC might be a better option, since you could carve out the pockets starting at the shallow end rather that plunging straight down with a Forstner. The problem you face is getting the trunnions in the same identical plane - a 3 dimensional geometry problem. Good luck, and let us know how you solve it. :)

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PostPosted: Wed Feb 20, 2019 2:40 pm 
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Getting the trunnions in the exact same plane was a trick. I bet I measured 50 times.
I made a paper template 1 1/2" wide and about 11" long. I marked the center on it and the two points I wanted for centers.

I wrapped the paper around one of the barrel halves and adjusted it back and forth until I had it centered on the top of the barrel. Then I tucked the ends under the flat part of the barrel.

I marked the hole then repeated the process on the other half. I bet I measured 50 times with a flexible tape measure until I was sure I had it right.

Then I bored a 2.25" hole in each half.
Turned the trunnions on the lathe, cut them to size, and glued them it.

When the glue dries, I'll dress up the joint with some wood filler to make it look seamless.
Then it's getting packed up and sent to Idaho.

My deal with the cannon foundry is a trade. I'm trading the wooden form for the first barrel that is cast from it. My plan would then be to build a naval carriage for it and put it up for sale.

Anyone need a cannon? :roll:

Zulu

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PostPosted: Wed Feb 20, 2019 3:22 pm 
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Zulu wrote:
Getting the trunnions in the exact same plane was a trick. I bet I measured 50 times.
I made a paper template 1 1/2" wide and about 11" long. I marked the center on it and the two points I wanted for centers.

I wrapped the paper around one of the barrel halves and adjusted it back and forth until I had it centered on the top of the barrel. Then I tucked the ends under the flat part of the barrel.

I marked the hole then repeated the process on the other half. I bet I measured 50 times with a flexible tape measure until I was sure I had it right.

Then I bored a 2.25" hole in each half.
Turned the trunnions on the lathe, cut them to size, and glued them it.

When the glue dries, I'll dress up the joint with some wood filler to make it look seamless.
Then it's getting packed up and sent to Idaho.

My deal with the cannon foundry is a trade. I'm trading the wooden form for the first barrel that is cast from it. My plan would then be to build a naval carriage for it and put it up for sale.

Anyone need a cannon? :roll:

Zulu

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Zulu


I had no doubt you would figure it out. Which makes one wonder what the cannon makers 200+
years ago figured out for this problem, given the tools available at the time. :wink: .

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PostPosted: Wed Feb 20, 2019 4:33 pm 
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Gene,
Cannon makers 200 years ago?
This is what they did in the 1500's and 1600's.
These are called dolphins. They are cast into the top of a barrel in the initial pour into sand.

Those guys are the ones with talent.
Zulu


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And don't forget stuff like this.

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PostPosted: Wed Feb 20, 2019 7:49 pm 
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Hey Zulu,

Looks good. I am confused though as to why the trunions are off center?

Also, the bore inserts added to the molds look as though they're permanent sleaves, is that so? I assume that this will be a shooter.

Cheers,
Tom

Ps. What inscription will be on the barrel? Surely something if only the date of casting.

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PostPosted: Thu Feb 21, 2019 7:34 am 
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tms wrote:
Hey Zulu,

Looks good. I am confused though as to why the trunions are off center?

Also, the bore inserts added to the molds look as though they're permanent sleaves, is that so? I assume that this will be a shooter.

Cheers,
Tom

Ps. What inscription will be on the barrel? Surely something if only the date of casting.



Hi Tom,
Most early cannons had below center trunnions. I don't really know why.
When a barrel like that sits on a carriage, it seems to me to be sitting way too high.
It makes the leveling wedge have to be pretty tall to allow the gun to shoot in the level position.

The cast barrel will be a shooter. In this case, the "liner" is cast into the barrel. It is made of modern steel and actually could handle the pressures of firing all by itself.
Most modern barrel makers use liners for safety reasons.
Some are cast in place. Others bore out a solid casting and epoxy and press in the liner.

Barrels that don't have a liner should meet what is referred to as the 3 to 1 rule. That is that the area of the breech that surrounds where the initial explosion takes place should equal the size of the bore.

1" bore = 3" breech.
3" bore = 9" breech.

The area behind the bore must equal the bore size also.
This is a general safety rule that is mostly ignored by some folks selling pipe bombs on Fleabay.

One of the trunnions will be stamped with the letter "H" for the Hern Ironworks Foundry.

Zulu

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PostPosted: Thu Feb 21, 2019 11:41 am 
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Here is a short video on how cannons are made. This is a different manufacturer than the one I am working with.
In this case, the barrel is bored out and a liner installed as opposed to pouring with the liner in place.
Zulu


https://southbendreplicas.com/how-barrels-are-made/

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PostPosted: Thu Feb 21, 2019 4:10 pm 
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Sorry, I was a day late and a dollar short so tried to delete my post. Ended up just erasing it.

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Last edited by DennisS on Thu Feb 21, 2019 4:19 pm, edited 1 time in total.

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PostPosted: Thu Feb 21, 2019 4:18 pm 
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Thanks Dennis,
Already got it done!
It does not get bored.
Zulu

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