in need of some help

[halfarod]

So this is my first post and I'm in the process of building my first cannon. The problem is that I'm not exactly sure how to do the contouring for trunnions..Any suggestions?

[Victor3]

 Hi halfarod,

 Do you mean the contour of the barrel where the trunnions are attached?

[Cat Whisperer]

halfarod --

WELCOME to the board!

There are several methods of attaching trunions, from casting them with the tube to banding to 'spot facing', welding and bolting.

What tube do you have in mind?  There are several threads here that one can search and find a wealth of info.  More directly, keep asking questions and the good folks here will answer.

[halfarod]

Well I got the idea from a website, so I turned the barred out of 1026 cold rolled, and is 6.5" O.D at the breech and has a 3" bore. So the place that I want to have the trunnions the O.D is 6". I have everything else done and welded on just can't figure the contouring for the trunnions out. I want to contour the so they will fit to the 6" O.D and then be welded on. So hopefully that little bit of info can get some help thrown my way
thanks

[Double D]

I think what you are realy saying is how do you attach trunnions. First that is something you should have planned before you started...but we are beyond that now, so let see if we can help.

In our sticky at the top of the forum we have one called safe loads and cannon plans. In there is a link to this thread http://www.gboreloaded.com/forums/index.php/topic,157566.0.html on putting in Trunnion pocket on in a drill press.   You are going to have to locte them so the perponderance is to the rear.  That is the the rear of the barrel is heavier than the front of the barrel.

Post up a picture of your barrel so we can see what you got and maybe help you.

[armorer77]

Greetings to a new cannon cocker ! Try inletteng the sides of your barrel with a center cutting end mill .0001" press fit works for me . Weld around . What is your chamber dia. ? you may not have enough wall at only .5 wall ratio . Armorer77

[Double D]

Armor77 has picked up on a very important point.  Both N-SSA and AAA require one full calibar wall thickness around the chamber to be safe.  If you have a 3 inch bore you need a 9 inch diameter around the chamber in all directions for safe wall thickness.

The largest safe bore size for 6.5 is 2.166

[halfarod]

Well what I did when i made the chamber I took a piece of 3.25" dia. stock a bored it so the place of ignition is 1.5"x2"... I'll post some pics so you know what I got going on.

[halfarod]

Sorry, the chamber is welded in.. I kept the O.D at 6.5" at the breech and 6.25" where i want to attach the trunnions.

[armorer77]

From the photos it looks like you used all the safety factors correctly . I would use a 2' trunnion , inset no more than .500"  .00005 to .0001 press fit and welded MIG or TIG if your machine will get hot enough for a secure bond . Armorer77

[dan610324]

sorry if I will come with a bit of a stupid question here , but you said you welded the chamber in the barrel .
could you please explain that a little better ??

did you turn the chamber slightly undersized and pushed it into the barrel and welded it in place from the breach end ??  or ??

if possible make an simple sketch and show how its done .

[halfarod]

When I faced the breech end, I bored the 3" to 3.25" and 7" in. So when i bored out the chamber piece, i made the I.D 3" so it matched the I.D of the barrel. I also turned the breech part of the chamber, I turned the 3.25 down to 1.5" and 1.5 long so I have a very good weld in there