What happens inside the bore when you pull the landyard?

[Parrott-Cannon]

Several months ago I posted an exterior ballistics program.  One of the requests was for a method to estimate muzzle velocity.  I have been working on an internal ballistics program to estimate muzzle velocity and pressure for smooth bore cannons and mortars.  The program is nearing completion (mortars and howitzers have not been programed).

As part of the program validation for cannons I found a report written by Capt. Rodman that details experiments conducted at the Washington Aresenal in 1844 - 1845 an a budget of 5000 dollars.  The google book reference is attached.  I have also attached a Table (word doc) comparing the program output with Rodman's data on a 1841 6 pounder.

I have also attached a program that addresses the internal ballistics of:  Nepolean, 6 pounder, Ordance Rifle, Dom Parrott and DOM French 75.  The velocity and pressures are dead on with published data or experimental data.

This test program show the velocity, pressure, acceleration, bore travel, energy balance, temperature and powder burned for 5 cannon listed above.  The Ordance Rifle data is from the safety study in published in the Artilleryman Magazine.

The most frustration thing about developing this program was the lack of good thermodynamic data on black powder.  I finally gave up and paid for the appropriate laboratory tests (not cheap).






http://books.google.com/books?id=1646AAAAcAAJ&pg=PA302&lpg=PA302&dq=Musket+Powder+Charge+Velocities&source=bl&ots=KFWoCpYVBr&sig=DO6heAv-zSZTcncGnvcJSgB7U-0&hl=en&ei=LaCrTKGcOIH-8AbLueGcCA&sa=X&oi=book_result&ct=result&resnum=8&ved=0CCsQ6AEwBw#v=onepage&q=Musket%20Powder%20Charge%20Velocities&f=false

[dan610324]

the velocities seem to be amazingly correct , but why the hughe and odd differences in pressure ??
lower in one end and higher in the other

[Parrott-Cannon]

the velocities seem to be amazingly correct , but why the hughe and odd differences in pressure ??
lower in one end and higher in the other

In this experiment Rodman was studying the effect of particle size on velocities and pressure.  The powder particle size is shown in the first column.  Three shots were made with each particle size of powder.  The particle size was calculated from the number of particles in 100 grains of each powder
granudation.  Current cannon grade powder would give a particle size by this method of approximately 3.5 mm - I am not going to count fg and ffg powder.


John

[Parrott-Cannon]

the velocities seem to be amazingly correct , but why the hughe and odd differences in pressure ??
lower in one end and higher in the other

Rodman's method for pressure was not detailed in the report.  It was not a crusher gauge.  Later publications call his pressure measurment methods into question.  The program calculates the velocity based on the pressure, projectile mass, and bore area at 0.01 milliseconds intervals - about 3000 data points during the firing.  If you do not have the pressure you do not have the velocity.