Pressure Producted by Different Powders

[Parrott-Cannon]

These pressure were measured in a 24 inch rifled barrel with 120 grains of each powder firing a 250 grain 50 cal. bullet.  The data provides an interesting comparison of 3 different granulations and powder from two different manufactures.
The energy released based on pressure:
2570 ft-lb for the Goex 2fg - 2.52 ms - projectile exit time
2272 ft-lb for Schuetzen 2fg - 2.92 ms - projectile exit time
619 ft-lb for the Goex Cannon - 3 ms - projectile exit greater than 3 ms
1399 ft-lb for Schuetzen 1fg - 3 ms - projectile exit greater than 3 ms
 

[Artilleryman]

What was the bore diameter?

[Parrott-Cannon]

What was the bore diameter?

50 cal.

[Double D]

The energy part is simple to understand.  Can you explain the projectile exit time, is that how many milliseconds it take for the projectile leave the barrel.  You convert that to the more standard fps.

This seems to correlate with Artilleryman and Switliks tests.

[Parrott-Cannon]

The energy part is simple to understand.  Can you explain the projectile exit time, is that how many milliseconds it take for the projectile leave the barrel.  You convert that to the more standard fps.

This seems to correlate with Artilleryman and Switliks tests.

The projectile time is in ms.  Using numerical analysis it is possible to calculate the projectile travel, acceleration, velocity and energy at each 0.01 ms.  When the bore travel exceeds the effective bore length (the bore length - the lenght occuppied by the powder), the projectile has exited the barrel.  In the cases presented the effective bore length is 1.667 feet and the projectile fired with Goex 2 fg moved 1.667 feet in 2.52 ms.  The measureing device records only 3 ms.  So if a projectile does not move 1.667 ft in 3 ms it did not exit the barrel in 3 ms.  Even with this recording limitation it provides a method of comparsion that I have not acheivied before. 

[Cannon Cocker]

Very interesting stats.  The often stated idea that the velocity from cannon and 1F is close or equal even though the pressure is not, cannot be shown by this data because it only shows that the time is an unknown amount greater than 3 ms on each of these.  They are also different powders (manufacturers).

[Double D]

Perhaps Parrot cannon can explain it better.

But is looks like to me that Fg is developing higher pressure faster, and has virtually the same  velocity as Cannon grade when it leaves the barrel.

[Cat Whisperer]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

[Parrott-Cannon]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocity data was not provided in the orginal post.  The energy data is calculated for the space mean pressure which is recorded by the Pressure Trace II.  The space mean pressure must be corrected for projectile and air friction to obtain vekocity.  The effective of pressure on velocity and energy is cummulative.  The calculated velocities are based on the corrected space mean pressure are:
Goex 2fg - 1578 fps
Schuetzen 2fg - 1513 fps
Goex Cannon - 840 fps - bore travel in 3ms - 0.84 feet
Schuetzen 1fg - 1188 fps -  bore travel in 3ms - 1.4 feet
 

[Double D]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocities are there.  The barrel is 24 inch long and the time it takes for the ball to leave the bore in ms, time and distance equals velocity does it not?

[Parrott-Cannon]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocities are there.  The barrel is 24 inch long and the time it takes for the ball to leave the bore in ms, time and distance equals velocity does it not?

First the projectile is seated on top of the powder and the ignition plug also takes up space so the distance traveled is the effective barrel length or in this case 1.667 feet.  For the Goex 2f, using your suggested calculation, a velocity of 661 fps is obtained (1.667/0.00252 seconds).
The correct basic calculation are:
acceleration = (Pc*Area)/Pm
velocity (Vi)=acceleration*time - Time = 0.0001 seconds for the pressure interval
Total Velocity = sum(Vi) in this case the Pressure Trace II records 300 pressure data points.  So there are 300 Vi that are added together to get the total velocity or muzzle velocity.  For the Goex 2fg example the peojectile exited the barrel at 2.52 ms so 252 data points were used in the velocity calculation.
Pc - Space Mean Pressure - Friction Pressure do to air drag and projectile friction with the barrel
Area - the area of the base of the projectile
Pm - the mass of the projectile
These equation are simplified from the actual calculations but are correct in principle.
 
 

[Double D]

Time of travel over set distance is velocity is it not?   

Also barrel length is measured from breech face to muzzle.  Barrel length above is 1.667 plus the amount space occupied by the charge.

Perhaps I am confusing speed with velocity.

[Parrott-Cannon]

Time of travel over set distance is velocity is it not?   

Also barrel length is measured from breech face to muzzle.  Barrel length above is 1.667 plus the amount space occupied by the charge.

Perhaps I am confusing speed with velocity.

Time of travel over a set distance is the average velocity.  If you travel 5 miles at 30 miles per hour and then 5 miles at 60 miles per hour.  The time of travel is 0.25 hours or an average velocity of 40 miles per hour.  Velocity is a vector so direction can also part of the equation.  However in this case velocity and speed are the same.  I will assure you that the projectile moved a measured distance of 1.667 feet.
The shape of the pressure curve is a function of the powder burning rate, which is pressure dependent, and the amount of gas generated during the burn.  It is also impacted by the amount of solids produced because this reduces the volume in which the gas expands.

[Double D]

It very simple for me, your approach is that of a scientist, I am just layman.,

[Parrott-Cannon]

It very simple for me, your approach is that of a scientist, I am just layman.,

You ask very good questions and you have always been helpful in correcting my terminology.  I am planning to develop data for 4 different powder manufactures.  I wish I could buy a bomb calorimeter to make the comparsions.  They are about $20,000.

[Microboomer]

Very interesting!
How do you measure pressure - do you have a sensor built into a breech plug?

Sounds like you need to find a university researcher that has a detonation calorimeter - I'll bet there aren't that many that get continuous use, and BP is going to stress the bomb less than the modern stuff that they're likely to be running tests on.  I have a colleague that has done some work on testing and remediation of explosives in soils.  It's a long shot, but I'll ask if he knows anyone doing thermodynamics work.
andy

[Parrott-Cannon]

Very interesting!
How do you measure pressure - do you have a sensor built into a breech plug?

Sounds like you need to find a university researcher that has a detonation calorimeter - I'll bet there aren't that many that get continuous use, and BP is going to stress the bomb less than the modern stuff that they're likely to be running tests on.  I have a colleague that has done some work on testing and remediation of explosives in soils.  It's a long shot, but I'll ask if he knows anyone doing thermodynamics work.
andy

The strain gage is attached to the outside of the barrel with a special glue.  Thank you for checking with your friend.
 

[Cat Whisperer]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocities are there.  The barrel is 24 inch long and the time it takes for the ball to leave the bore in ms, time and distance equals velocity does it not?

The projo may be in the tube for X seconds and it travels Y distance, BUT it does not travel at a constant velocity(speed) it is accelerating from 0 fps to SOME fps when it exits.  Unless you know the acceleration you won't be able to calculate the velocity.  But he has measured it at the muzzle (or the program has the algorithm to calculate it).

Agree good discussion.

[Parrott-Cannon]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocities are there.  The barrel is 24 inch long and the time it takes for the ball to leave the bore in ms, time and distance equals velocity does it not?

The projo may be in the tube for X seconds and it travels Y distance, BUT it does not travel at a constant velocity(speed) it is accelerating from 0 fps to SOME fps when it exits.  Unless you know the acceleration you won't be able to calculate the velocity.  But he has measured it at the muzzle (or the program has the algorithm to calculate it).

Agree good discussion.

It is possible to cal. the acceleration from the pressure.  The velocity is the accereraltion x time for the time the pressure is applied - for this set up every 0.0001 seconds.  The velocity for each interval is summed to get the total velocity.  The velocity x time is the distance traveled and allows the determination of the time the projectile exits the barrel.

[Double D]

In layman speak, speed and velocity are the same thing.  In science talk they are different. 
 

[onegreatshot]

Whew that was a hard read.

[Cat Whisperer]

If, as I think that ms = milliseconds (1/1000 sec) that the velocities are not on the chart.

Velocities are there.  The barrel is 24 inch long and the time it takes for the ball to leave the bore in ms, time and distance equals velocity does it not?

The projo may be in the tube for X seconds and it travels Y distance, BUT it does not travel at a constant velocity(speed) it is accelerating from 0 fps to SOME fps when it exits.  Unless you know the acceleration you won't be able to calculate the velocity.  But he has measured it at the muzzle (or the program has the algorithm to calculate it).

Agree good discussion.

It is possible to cal. the acceleration from the pressure.  The velocity is the accereraltion x time for the time the pressure is applied - for this set up every 0.0001 seconds.  The velocity for each interval is summed to get the total velocity.  The velocity x time is the distance traveled and allows the determination of the time the projectile exits the barrel.

But the pressure changes over time, and resistance to motion (friction) would be another variable.  Agree, you could come prety close, and there would be some shot-to-shot variation as well.

Velocity (in physics) is a vector quantity.  A vector that to be fully described is both speed and direction.

[Parrott-Cannon]

For those who think high pressure is the answer to velocity examine the pressure curves for thr Goex and Schuetzen 2 fg powders.  The Goex powder has a much higher pressure than the Schuetzen but the Schuetzen powder maintains its pressure for a longer peroid resulting in only a 4% lower velocity.  Most black powder arms produce about a 7% variability in velocity in a shot string.
 

[Cat Whisperer]

For those who think high pressure is the answer to velocity examine the pressure curves for thr Goex and Schuetzen 2 fg powders.  The Goex powder has a much higher pressure than the Schuetzen but the Schuetzen powder maintains its pressure for a longer peroid resulting in only a 4% lower velocity.  Most black powder arms produce about a 7% variability in velocity in a shot string.

In single shot rifle competition, the variability of blackpowder is often MUCH LESS than for smokeless powder (because of how it burns - more regular burn despite higher pressure).  Not unusual to see single digit standard deviations when looking at velocities using black, usually much more variation with smokeless.

[Parrott-Cannon]

For those who think high pressure is the answer to velocity examine the pressure curves for thr Goex and Schuetzen 2 fg powders.  The Goex powder has a much higher pressure than the Schuetzen but the Schuetzen powder maintains its pressure for a longer peroid resulting in only a 4% lower velocity.  Most black powder arms produce about a 7% variability in velocity in a shot string.

In single shot rifle competition, the variability of blackpowder is often MUCH LESS than for smokeless powder (because of how it burns - more regular burn despite higher pressure).  Not unusual to see single digit standard deviations when looking at velocities using black, usually much more variation with smokeless.

Single digit standard deviations occurs when the optium powder load is used.  The standard deviation is a minimum at the optium powder load.

[Cat Whisperer]

For those who think high pressure is the answer to velocity examine the pressure curves for thr Goex and Schuetzen 2 fg powders.  The Goex powder has a much higher pressure than the Schuetzen but the Schuetzen powder maintains its pressure for a longer peroid resulting in only a 4% lower velocity.  Most black powder arms produce about a 7% variability in velocity in a shot string.

In single shot rifle competition, the variability of blackpowder is often MUCH LESS than for smokeless powder (because of how it burns - more regular burn despite higher pressure).  Not unusual to see single digit standard deviations when looking at velocities using black, usually much more variation with smokeless.

Single digit standard deviations occurs when the optium powder load is used.  The standard deviation is a minimum at the optium powder load.

Optimum meaning?  Perhaps a balance of the variables (ID, amount of powder, granulation, mass of projo, windage) such that the pressures produced fall within a range that allows consistant burning?  (Meaning if the pressure is too high or too low there will be more variation in burn rate?)

Does this imply that the rate of burn could oscillate (faster/slower) under some conditions and be more linear under specific conditions?

[Parrott-Cannon]

For those who think high pressure is the answer to velocity examine the pressure curves for thr Goex and Schuetzen 2 fg powders.  The Goex powder has a much higher pressure than the Schuetzen but the Schuetzen powder maintains its pressure for a longer peroid resulting in only a 4% lower velocity.  Most black powder arms produce about a 7% variability in velocity in a shot string.

In single shot rifle competition, the variability of blackpowder is often MUCH LESS than for smokeless powder (because of how it burns - more regular burn despite higher pressure).  Not unusual to see single digit standard deviations when looking at velocities using black, usually much more variation with smokeless.

Single digit standard deviations occurs when the optium powder load is used.  The standard deviation is a minimum at the optium powder load.

Optimum meaning?  Perhaps a balance of the variables (ID, amount of powder, granulation, mass of projo, windage) such that the pressures produced fall within a range that allows consistant burning?  (Meaning if the pressure is too high or too low there will be more variation in burn rate?)

Does this imply that the rate of burn could oscillate (faster/slower) under some conditions and be more linear under specific conditions?

I agree with optimazation list.  However, burn rate is a function of pressure, powder particle size, powder particle shape, density (hardness) and if the powder has been polished to remove fines clinging to the powder particles.  The optium combination does produce lower pressures over a longer time peroid and proablely assures a more complete burning of the powder.  I am gussing but I beleive in an optium load the powder moves as a tight plug right behind the proj.  With to strong a charge the powder spreads out more and the ignition is not consistent and due to the higher pressures the proj. exits the barrel before the burn is complete.  With a low charge the pressure so not acheive a sufficient pressure to cause and effect burn to take place.

[Parrott-Cannon]

The burn rate graph shows how the burn rate changes with pressure:

Notice how the burn rate is expoential to about 5 atm and then becomes linear.

[Microboomer]

Parrott,
No luck with my friend - he's a soil scientist and the best he had was "Well, I heard this guy from Aberdeen give a talk once..."

This post got me interested in chamber pressure measurements in general.  Maybe everyone else is familiar with the concept, but I found an article with a good description of a DIY setup:
http://www.ktgunsmith.com/straingauge.htm
andy

[Parrott-Cannon]

Parrott,
No luck with my friend - he's a soil scientist and the best he had was "Well, I heard this guy from Aberdeen give a talk once..."

This post got me interested in chamber pressure measurements in general.  Maybe everyone else is familiar with the concept, but I found an article with a good description of a DIY setup:
http://www.ktgunsmith.com/straingauge.htm
andy

Andy
Thank you for the info.
 
John