Auto CAD drawing of my MINI

[TheMachinist]

Here is what I have came up with for my mini cannon Material im using is 932 Naval brass. I was wondering if someone could tell me if im going to have enough wall thickness to attach the trunions (I think thats spelled right)? Thanks for the help in advance got to say this is the most helpful forum I am a member of.
 

[Doc Brown.]

It looks perfect to me as far as walls go but you might benefit from moving the vent back some. But then again this thing is pretty small. Chances are you will defiantly have enough powder in there to go off.

[TheMachinist]

It looks perfect to me as far as walls go but you might benefit from moving the vent back some. But then again this thing is pretty small. Chances are you will defiantly have enough powder in there to go off.

Thanks dock and im glad you pointed that out I will be moving the vent hole back would you use screw in trunnions or would you silver solder them and how deep would you make the pockets?

[GGaskill]

Silver soldering would be stronger but would likely anneal the brass too much.  One reason to use steel instead of brass.  Even with fine pitch threads, you aren't going to get many in the limited amount of wall thickness you have.  If you used a trunnion ring that was external to the barrel, you could silver solder to that before pressing it on the barrel.

[TheMachinist]

Silver soldering would be stronger but would likely anneal the brass too much.  One reason to use steel instead of brass.  Even with fine pitch threads, you aren't going to get many in the limited amount of wall thickness you have.  If you used a trunnion ring that was external to the barrel, you could silver solder to that before pressing it on the barrel.

Okay im so what if I drilled .1095 deep and tapped them and epoxed them in being as small as the cannon is this still safe? sorry if im asking a lot of questions just trying to make this as safe as possible

[Cat Whisperer]

Good drafting style (I taught Drafting/design - AutoCAD for 13 years).

The 1/3 rule on ID compared to OD is for the area around where the pressure peak occurs.  The pressures are much less further down the tube.  THEREFORE the wall thickness can be a bit thinner - safely.

Good questions!

You might want to remove the sharp inside corner (cut by the drill) by rounding it or cutting a spherical end to the hole.  That will greatly reduce stress risers.

[TheMachinist]

Good drafting style (I taught Drafting/design - AutoCAD for 13 years).

Thanks for the compliment been drafting for about two years now and love every minute of it. Thanks for the pointers on the wall thickness now that I got that cleared up I can start my gun tube this weekend.

[GGaskill]

Okay im so what if I drilled .1095 deep and tapped them and epoxed them in being as small as the cannon is this still safe?

That would probably leave satisfactory wall thickness but even using 32 TPI, you aren't going to get many threads in there; probably only a couple even using a bottoming tap.  True, you aren't going to have much recoil with this. It won't be a safety issue then, only one of robustness of the barrel.

[TheMachinist]

Robustness of the barrel? Are you saying its gonna be to weak the way I have it designed?

Okay im so what if I drilled .1095 deep and tapped them and epoxed them in being as small as the cannon is this still safe?

That would probably leave satisfactory wall thickness but even using 32 TPI, you aren't going to get many threads in there; probably only a couple even using a bottoming tap.  True, you aren't going to have much recoil with this. It won't be a safety issue then, only one of robustness of the barrel.

[GGaskill]

I am referring to the trunnion attachment, not the ability of the tube to resist the explosion.

[TheMachinist]

I am referring to the trunnion attachment, not the ability of the tube to resist the explosion.

Ah... Sorry for the miss understanding.

[GGaskill]

No problem.  Forums and email are somewhat lacking in the instant feedback of face to face conversation.