Punt Gun Videos

Status
Not open for further replies.
arcticap

arcticap

Member
Joined
Mar 20, 2005
Messages
8,717
Location
Central Connecticut
Someone should tell him that the hoop stress in the chamber increases proportionally to the increase in radius. That is the stress pulling the steel apart and making the chamber want to rupture open - not the same as the internal pressure of gasses inside the chamber.

The formula for thin wall pressure vessels is

Hoop stress (psi) = Gas pressure (psi) * radius of vessel (inches) / wall thickness (inches)

The amount of force in pounds exerted on the breech of the gun is just the internal gas pressure (psi) x the cross sectional area (square inches).

That is based on absolute pressure in psi, I don't know what CUP measurements are or the conversion between the two. I don't know how you could determine the pressure generated other than to figure a complete combustion into gas of all the combustable materials occupying the original volume as a worst-case scenario. I don't know if the powder manufacturers list that info or not, like on a psi pressure to original grains volume basis.

A thin wall is usually considered less than 1/10th of the inside diameter, whereas it looked like the pic in that link it was more than that. Even so, unless that is a heat-treated alloy tube, he would be well advised not to exceed a 6000 psi hoop stress on a regular basis to rule out low-cycle fatigue failure.

There's some mechanical engineering input for him. It's worth exactly what it cost. hahaha
 
Status
Not open for further replies.
Back
Top