VP-SIM an Internal Ballistics Program

[Parrott-Cannon]

I have been working on this program for over a year.  I measured velocities, fired my cannons hundreds of times, and spent many hours

researching for historic data and have written over 50,000 lines of code.  The program developed from this effort I call VP-SIM.

VP-SIM is an internal ballistic program for black powder, smooth bore, cannons or muskets.  It is a modification of the US Army Lumped

Parameter model.

VP-SIM has been validated for 11 different black powder cannon or muskets with multiple powder charges and projectiles weights.  VP-

SIM correctly predicted the velocity within 7% of the known values.  The spread sheet documenting these results is attached as Appendix A in the operating manual.

VP-SIM does not produce smoke, fire, or noise and does not require clean up.  VP-SIM has a simple user interface and provides a

mathematical model to:

* Determine muzzle velocity – using the standard parameters VP-SIM calculates muzzle velocities    within 7% of the known value.

* Determine powder charge on velocity and pressure.

* Determine the effect of various powder granulations on muzzle velocity and pressure.

* Determine the effect of barrel length on muzzle velocity and pressure.

* Determine amount of powder charge burned.

* Study the effects of ignition efficiency on muzzle velocity and pressure.

* Study projectile diameter on muzzle velocity and pressure.

I would appreciate your constructive input on this version of the program.  It will be expanded in the future to include mortars and

howitzers.

Enjoy the program!

Down load the attached zip file – unzip – click on the setup icon.

No claim is made as to the accuracy of VP-SIM on your weapon for either velocity or pressure.

P.S.  I had to post the program and instruction manual separately.

[Parrott-Cannon]

Instruction Manual

[Cat Whisperer]

Cleaning rifles right now, but will down load late this evening!

THANKS!

Question:  accurate within 7%  -  is that +/- 7%?

[Double D]

Parrot  Cannon.  I know you have been spending a lot time on this and it was time well spent.   Good Job!!!!!!

Back when I was still working as an  analyst, I once over heard a couple of the young programmers say "take it over to the old guy see if he can crash it".  I was the old  Guy.  I didn't crash yours.

First I did what most people will  do. I down loaded the program opened it up and started using it. The opening screen is very basic.  I started right off with with other  Golf Ball mortar and it worked!!!

After doing a couple of variations, I downloaded  and opened the instruction manual.  One of the opening statements in the  Manual sums up this program very well, "The program input is straightforward and intuitive".



I did not find •   VP-SIM’s Windows Menu .

Parrot-Cannon, thanks for building this for us...I already have it pinned to my start menu.

[Parrott-Cannon]

Cleaning rifles right now, but will down load late this evening!

THANKS!

Question:  accurate within 7%  -  is that +/- 7%?

You are correct it is plus or minus.  It not designed to work with mortars because of the chamberage issue.  I have had satisfactory results on mortars with full or nearly full chamber loads but as the powder charge decreases and the projectile weight decreases it becomes less accurate. 

[Parrott-Cannon]

Parrot  Cannon.  I know you have been spending a lot time on this and it was time well spent.   Good Job!!!!!!

Back when I was still working as an  analyst, I once over heard a couple of the young programmers say "take it over to the old guy see if he can crash it".  I was the old  Guy.  I didn't crash yours.

First I did what most people will  do. I down loaded the program opened it up and started using it. The opening screen is very basic.  I started right off with with other  Golf Ball mortar and it worked!!!

After doing a couple of variations, I downloaded  and opened the instruction manual.  One of the opening statements in the  Manual sums up this program very well, "The program input is straightforward and intuitive".



I did not find •   VP-SIM’s Windows Menu .

Parrot-Cannon, thanks for building this for us...I already have it pinned to my start menu.

I was refering to the File menu.

[Parrott-Cannon]

Double D thank you for the compliment.  File is in the windows menu.
         

[seacoastartillery]

    Parrott-Cannon, thanks for your excellent program and complete instructions.  The first thing I did was to ignore the instructions and input values for our Parrott 100pdr. Cannon.  Sure its rifled, but we just wanted to get an idea at what the pressure would be with our new 600gr. armor-piercing load.  The data I input and the calculated results are below.  What should I discount and what should be approx. correct??

Bore size.............1.067"
Projo size............1.063"
Projo weight........3,062.5 grs.
Powder weight....600 grs.
Powder gran........FFg
Max breech Press......21,353
% Powder burnt...............99.8

Whoops.  I forgot to report the velocity.  The program calculates it as 1,258 f.p.s. and our Crony chronograph consistently has
the velocity for this wt. of powder and bolt at 1,241 to 1,260 f.p.s.

Thanks again; your program is wonderful.  Oh, I did read the instructions, finally.  Nice graphics too.

Tracy & Mike

[Parrott-Cannon]

    Parrott-Cannon, thanks for your excellent program and complete instructions.  The first thing I did was to ignore the instructions and input values for our Parrott 100pdr. Cannon.  Sure its rifled, but we just wanted to get an idea at what the pressure would be with our new 600gr. armor-piercing load.  The data I input and the calculated results are below.  What should I discount and what should be approx. correct??

Bore size.............1.067"
Projo size............1.063"
Projo weight........3,062.5 grs.
Powder weight....600 grs.
Powder gran........FFg
Max breech Press......21,353
% Powder burnt...............99.8

Thanks again; your program is wonderful.  Oh, I did read the instructions, finally.  Nice graphics too.

Tracy & Mike

With a rifled cannon the fiction will be higher and the projectile dia. is a little larger.  The friction would increase and the pressure would increase and the velocity would be decreased,  the projectile dia. increase would increase velocity, It may be a wash.  I just purchased a rifled muzzle loader (0.69 cal) that I hope will provide data (pressure and velocity) that I can use to validate the rifled version of VP-SIM.  I have made some runs with rifled muzzle loader rifles producted by Traditions based on their ballistic data with acceptable results; If I recall correctly I increased the coef. of friction to 0.2 or 0.3 and used a projectile dia. equal to the bore diameter.  Thank you for your kind words about the program and manual.

[Parrott-Cannon]

    Parrott-Cannon, thanks for your excellent program and complete instructions.  The first thing I did was to ignore the instructions and input values for our Parrott 100pdr. Cannon.  Sure its rifled, but we just wanted to get an idea at what the pressure would be with our new 600gr. armor-piercing load.  The data I input and the calculated results are below.  What should I discount and what should be approx. correct??

Bore size.............1.067"
Projo size............1.063"
Projo weight........3,062.5 grs.
Powder weight....600 grs.
Powder gran........FFg
Max breech Press......21,353
% Powder burnt...............99.8

Whoops.  I forgot to report the velocity.  The program calculates it as 1,258 f.p.s. and our Crony chronograph consistently has
the velocity for this wt. of powder and bolt at 1,241 to 1,260 f.p.s.

Thanks again; your program is wonderful.  Oh, I did read the instructions, finally.  Nice graphics too.

Tracy & Mike

Thank you for the independent conformation of the muzzle velocity. 

John

[Will Bison]

Outstanding program.

I ran some numbers for my 47 mm rifled gun and compared them to some high speed photos. Seems your data is spot on. The camera of course only tells the bore time and the muzzle velocity.

With the VP-SIM loaded on the laptop and the camera also hooked up, I'll have something new to play with.

Again , great job.

Bill

[Parrott-Cannon]

Outstanding program.

I ran some numbers for my 47 mm rifled gun and compared them to some high speed photos. Seems your data is spot on. The camera of course only tells the bore time and the muzzle velocity.

With the VP-SIM loaded on the laptop and the camera also hooked up, I'll have something new to play with.

Again , great job.

Bill

Thank you for the feed back

[Johnaf16]

Wow, this program rocks!  When will the mortar version be available?  I have a great deal of velocity data on verious cannons and this program provides execellent agremment with my data.  Thank you for your efforts.

[gulfcoastblackpowder]

I've tinkered with this program a little, but not enough to give you proper feedback.  Thanks, though for making it.  It has been interesting so far. 

I just tried to run numbers for a microcannon:
Bore Length:1.00in
Bore Dia:0.189in
Projectile Dia:0.177in
Projectile Weight:5gr
Charge:3.5gr (2f - prefer 3f or 4f, but they aren't options)
Recoil Weight:0.25lb
Vent Diameter:0.0625in

I get an error: "An abnormal calculation occurred"  I haven't looked at it too much, so I don't know if I'm trying to make the program extrapolate experimental data too far or if somehow I've caused a div0 error somewhere (though that doesn't make sense to me), or some other logic anomaly due to the formulae used in the program's constraints. 

Perhaps you can tell me why it doesn't work?

[Parrott-Cannon]

I've tinkered with this program a little, but not enough to give you proper feedback.  Thanks, though for making it.  It has been interesting so far. 

I just tried to run numbers for a microcannon:
Bore Length:1.00in
Bore Dia:0.189in
Projectile Dia:0.177in
Projectile Weight:5gr
Charge:3.5gr (2f - prefer 3f or 4f, but they aren't options)
Recoil Weight:0.25lb
Vent Diameter:0.0625in

I get an error: "An abnormal calculation occurred"  I haven't looked at it too much, so I don't know if I'm trying to make the program extrapolate experimental data too far or if somehow I've caused a div0 error somewhere (though that doesn't make sense to me), or some other logic anomaly due to the formulae used in the program's constraints. 

Perhaps you can tell me why it doesn't work?

Thank you for providing the input data you used.  The error "An abnornal calculation occurred" can be attributed to no less than 10 different calculation errors.    In this case the error occured in the windage calculations.  When I designed the calculation for windage I never considered the need to test for "non-chocked flow" or that the program would be used on microcannons.  In a microcannon the flow rate of gases due to windage in the current program is to high resulting in out of limit pressure change.

I will correct the calculation in the next version of VP-SIM which I will issue when I complete the subroutines for mortars.

A work a round:

Set the Bore Diameter and projectile Diameter to the same value.  In your case I would use 0.177. 

If you want an approximate calculation using fffg set the Burn Rate Constant to 1.25 and select the ffg radiobutton.

If you want an approximate calculation using ffffg set the Burn Rate Constant to 1.55 and select the ffg radiobutton.

There are 5 factors that must be determined to setup a different black powder granulation.  I do not currently have plans to spend the funds for determining these factors for fffg or ffffg.   

[gulfcoastblackpowder]

Thank you for the response! 

I will try out these numbers using the workarounds you mention.  I'm also considering a much smaller bore...but that's a secret ...du'oh!