On cannons -- wall thickness ?

[PeteH]

A question about cannons... which probably has been addressed numerous times already; but I can't find it with the "Search" function.

I believe I've read that the wall thickness at the breech should be at least one bore-diameter; e.g. a 1" bore gun should have an OD of 3" at the breech. Is this universally true ? Seems to me that it's a bit excessive for small-bore (under 2") cannon, especially those made of modern steels; and conversely, may be on the light side for large-bore guns.

Reason: I'm thinking of making a Parrott-type gun (smoothbored) out of seamless DOM tubing, shrink-fitting a sleeve over the breech end to reinforce it; and then doing whatever turning is necessary after the fact. Considering the strength of DOM tubing, does that "rule" still apply ?

Any comments ?? Thanks in advance.

[hammermill]

i would suggest a look here at graybeard outdoors do a lot of checking before starting to make sure it will be allowed to shoot at many ranges etc.

http://www.go2gbo.com/forums/index.php/ ... 814.0.html


as advised cannons are not just big blackpowder guns and you want it safe as long as it exists

enjoy the project

[PeteH]

Thanks! I'd found the Greybeard site some time ago, bookmarked it, then promptly forgot about it. This time, I bookmarked it in several different folders. Maybe THAT will aid my fading grey cells.

It looks like a very comprehensive info source.

Clearly, there's great concern about safety - and I can see from some of the linked sites, how some people might see the "rules and regulations" as excessive. But you don't want the thing turning into a bomb, nor do you want to repeat what those TV guys did last week.

[hammermill]

i think the tv guys didnt pay attention to things flying to the air. dont know havent realy seen much about it.


more important is a catastrophic failure of the chamber/barrel while people are standing by.

[GeorgeGaskill]

The wall thickness equals bore diameter rule applies only to the area where the charge lies and a couple of diameters in front of that. It is OK to taper the barrel from there to the muzzle. A Parrott style reinforcement would be adequate if if covers the same area.