A Ballistic question

[richardjeb]

Can anyone please help..... I am trying to calculate the centre of pressure for a small microlight subsonic projectile, does anyone know of anything that may help, computer programs, formulas etc. Any help would be much appreciated Thanks

[runfiverun]

in a cartridge fired projectile, the pressure pushes on the center of the projectile untill the end of the bbl.
at least that is where the maximum amount of force is applied.
on a round object i am not sure where it would be the highest but on a flat base it is the center.
maybe felix could help here?

[Tom Myers]

Can anyone please help..... I am trying to calculate the center of pressure for a small microlight subsonic projectile, does anyone know of anything that may help, computer programs, formulas etc. Any help would be much appreciated Thanks

Richard,

I put together the formulas and algorithms needed to calculate the center of pressure of bullets that are designed in the Precision Bullet Design and Evaluation Software. The procedures required many pages of code to do the job.

Basically the geometric center of the profile of each segment must be determined and then the areas of those segments times the distance of the centroid from the base of the projectile must be found and totaled. This is then divided by the sum of the product of each area times its distance from the base to arrive at the center of pressure.

This is the same method as is used to find the center of gravity of a projectile only the geometric centroid of each segment is considered as opposed to the center of mass of each segment used in the CG calculations.

The non regular segments such as cones, ogives, elliptical noses, and rounded grooves require special formulas, algorithms or numerical integration methods to calculate their geometric centroids.

Fortunately you can very closely determine the center of pressure (Not to be confused with the Center of Gravity) by making a scale cutout of the profile of the projectile from stiff paper or thin cardboard and then balance the cutout on the edge of a ruler or knife blade. That balance Point will be the center of pressure for a projectile with that profile.

Hope this helps. If you need more information, PM me.

Respectfully,
Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

[AZ-Stew]

I'll bow to Tom on the center of pressure, but for the center of mass, it can be easily found using a Computer Aided Design (CAD) solid modeling program. If you know any mechanical engineers or mechanical designers (and you do now: AZ-Stew), and can provide an accurate, fully dimensioned 2-D sketch of your design, the bullet can be modeled and the CoM can be instantly determined. I suspect this is what Tom's program does, but the info is available elsewhere.

Regards,

Stew

[runfiverun]

i think with as small a projectile as he is describing a model [unless a scaled up one]
would not be helpful.
he is gonna have to figure out the pressure point on the shape.