Cohorn trunnion?

[Doc Brown.]

Im trying to get my head around the best way to put a trunnion bar on cohorn mortar. I was wondering if this would be the easiest and most authentic way of doing it. Putting a radius in the bar itself is boggling my mind.
 

 
Heres my Small scale im working on. Its just a practice run and will not work if I go this route as I bored it to deep to do it the way I think I want to.

[Double D]

Some have done it that way. I would be a bit concerned about not having one caliber wall thickness

[Doc Brown.]

Ya I wouldn't do it on this one probably. I have a 5/8" powder chamber and theres not enough behind it to get 5/8 wall after a trunnion bar was put in the way I want to. I started on this little balloon popper without giving the trunnion bar much thought.  I did fire it and it sounded like a little tiny balloon pooping. It was very very disappointing.

[GGaskill]

That is the way I do it, but you have to cut the chamber to give you a good back wall.  It looks like yours is a little too deep, as for me, they work out to be about half a trunnion diameter into the tube.  The bronze ones I have done have been cast (with integral trunnion) while the fabricated ones have been steel with a welded trunnion, then bronze painted for coloration.

[Doc Brown.]

Im almost done with the golf ball cohorn. Check it out. I still need to attach the trunnion bar to it. Im just going to weld the bar onto it. This is 4" diameter 304 stainless close to 8" long without the bar.
This is my first golf ball cannon of any kind. I cant wait to see a golf ball flying through the air.
 

[GGaskill]

That looks strong enough to shoot the Fox steel golf balls with minimal risk.

[flagman1776]

I was struggling with this same issue when my cannon machinist suggested cutting a matching spherical socket in my oversized trunion bar & welding.  The unknown Naval Brass alloy (later tested) gave him a hard time welding but it allowed my propeller shaft mortar project to be completed.
http://www.gboreloaded.com/forums/index.php/topic,263220.msg1099564911.html#msg1099564911

[Doc Brown.]

This has been a long process for me making this golf ball mortar. Its finally done and I have some problems.
 
First off I took the advice on here and made my powder chamber based on my wall thickness at the breach. 1.25" seems just about right. Outside diameter is around 3.5" at the breach. Machined from solid 4" 304 Stainless steel.
I then looked up max load for a 1.25" powder chamber and I find it is to be around 300 grains or so. I make my powder chamber 1.25" by 2" deep.
 
I test fired it today and measured the powder in a powder measure. I used 300 grains. The ball couldn't be seen at any point in time. When I would reduce it to around 50 grain it could be seen. I tried 150 grain and again no ball to be seen. What is a charge size to play around with. 25 to 75 seem like it would be the sweet spot.
 
Im wondering if the ball exploded or something and thats why I couldn't see them. How far could a golf ball go with 300 grain?
I Used 3F black powder.
 
I guess im second guessing my powder chamber. Please tell me that theres some good that could come from this large powder chamber. Does it take more powder to shoot the steel ball. Would you ever need 300 grain 3F for anything.

 

[Double D]

Yes there is some good to come of this powder chamber....if you insist on filling it the powder sellers will be real pleased. 

Bottom line, don't worry about just go shoot.

[GGaskill]

It's too big, but it's water over the dam.  Lessen your charge; start with 25 grains and go up as experience teaches.  The golf balls are probably not exploding or they wouldn't go very far.  They are just going too fast and are relatively small and hard to see.  I know some people can't see bowling balls because they don't use the proper viewing technique.  Use strongly colored golf balls or paint the white ones some bright color that contrasts with sky.  Keep in mind that they will be half blackened by the burning powder.

[Doc Brown.]

That looks strong enough to shoot the Fox steel golf balls with minimal risk.

 
I was wrong about my powder chamber it is only 1" diameter. I messed up when I said it was 1.25" diameter.
 
I think there would be zero risk with any projectile. Its my personal opinion that 304 stainless is as good if not better than 1018 steel for cannons.
 
As you can see from my inside picture. I did run the boring bar into the wall there a bit. I tried to clean it up. Its hard to clean that up. I don't know what else to do to get the chatter marks out. 
 

[armorer77]

You can try a Flex Hone , but it will take a long time . They do no harm on the bottom . Ed