Joint Blog entry between Don Hansell and Hector Medina
First of all, thanks to Don for having a very slow "sticktion" and getting things done in a jiffy!
;-)
So, let's start at the beginning:
WHAT is efficiency?
The dictionary has one definition that helps us:
" - the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage."
Well, we will not use a percentage because in this context, we are dealing with different "forms" of energy.
I would propose to follow engineering criteria and express the efficiency of a PCP airgun as the ratio of the CC-BAR's needed to generate ONE ft-lb at the muzzle.
Before we continue with the discussion, it is important to clearly explain WHY we can compare a combined "unit" (CC-BAR) to another (ft-lb).
Well, we'll start by observing they are BOTH ways to measure ENERGY, and "energy" and "work" are identical concepts. Physics 101 tells us that "Work" is the "change in energy" of an object.
In a pellet, the energy at the muzzle is the work that the gun has exerted on it. IF the pellet was already travelling, we would have to subtract the initial energy from the muzzle energy, but since the pellet is stationary, the change is exactly the muzzle energy.
Now, WHY can we use the Ft-lbs as a measure of energy?
Think about lifting an object (by pleasure or not): If you lift a mass of 1# over 12" , you have just exerted 1 ft-lb of work. If you release that object at the time of hitting the ground, the object will transmit to the ground 1 ft-lb of kinetic energy.
An example from our world: We tend to think of 12 ft-lbs airguns as "Nerf" guns, that's for the Brits. We like guns with multiples of that energy, what on Earth could you possibly do with "just 12 ft-lbs"?
Well, consider this:
You go bowling, and the bowling balls at your lanes are all 12#. The channel where the balls come out is a bit low, for aesthetic purposes, and the channel is located at 12" above the floor.
Your girlfriend has never been bowling, and she does not really know how to take the ball, you approach her when you see that she is using just two fingers. She cannot really lift the ball and the ball is perched at the edge of the rail.
When you get to her, he turns around to face you and the ball drops on your small toe.
You have just been hit by 12 ft-lbs., and I doubt you have the same concept about what "Just 12 ft-lbs" is.
;-)
So, we have established that Ft-lbs IS a unit that measures ENERGY.
But, what about CC-BAR? How could that be an energy unit?
Well, C-C stands for Cubic Centimeters, that means cm³, and it is = cm x cm x cm (length x width x breadth).
And BAR is a pressure, so it is a FORCE applied over an AREA, in unit terms, we can say that 1 kg of mass, resting on a square that is 1 cm per side = approx 1 BAR (0.98 to be precise).
And so, if we Multiply cm³ X kg/cm², we get kg-cm, which is a unit of energy/work because it is force exerted over a distance; exactly the same way that ft-lb is. Remember that in multplication, the order of the elements does not affect the result, so kg-cm is the same as cm-kg, or, within the different systems ft-lb.
Just a note here: ft-lb IS DIFFERENT from lb-ft, the former is a unit of energy, the latter is a unit of TORQUE.
We have now achieved the understanding that we are measuring a PROPORTION of energies:
The energy that goes out of the air tank/tube/bottle and the energy that comes out as a speeding pellet.
In THIS context, our "efficiency" measure is perfectly reasonable. AND since we are observing HOW MANY cc-bar's are needed to create ONE ft-lb at the muzzle, it makes for easy comparison across platforms.
Obviously, the LESS cc-bar's are used per ft-lb, the higher the efficiency of any given system is.
Remember: a LOW value is GOOD in this context.
Some writers want to go the "strict physics" way and divide the total energy output by the pressure excursion, but that does not take into account the volume of the chamber (tube/tank/bottle), so it is only useful as a comparison for THAT specific situation, and changes under this method can be tricky to interpret.
OK, so now, armed with our knowledge, let's take some examples from the real world.
My good friend Stephen Archer has just published an article on the tuning of the Micro-Strike, I do encourage you to read it in full. Since we cannot insert here any of the txts, figures, or charts, I will quote the numbers on two interesting tests that are summarized in this table:
;-)
So, let's start at the beginning:
WHAT is efficiency?
The dictionary has one definition that helps us:
" - the ratio of the work done or energy developed by a machine, engine, etc., to the energy supplied to it, usually expressed as a percentage."
Well, we will not use a percentage because in this context, we are dealing with different "forms" of energy.
I would propose to follow engineering criteria and express the efficiency of a PCP airgun as the ratio of the CC-BAR's needed to generate ONE ft-lb at the muzzle.
Before we continue with the discussion, it is important to clearly explain WHY we can compare a combined "unit" (CC-BAR) to another (ft-lb).
Well, we'll start by observing they are BOTH ways to measure ENERGY, and "energy" and "work" are identical concepts. Physics 101 tells us that "Work" is the "change in energy" of an object.
In a pellet, the energy at the muzzle is the work that the gun has exerted on it. IF the pellet was already travelling, we would have to subtract the initial energy from the muzzle energy, but since the pellet is stationary, the change is exactly the muzzle energy.
Now, WHY can we use the Ft-lbs as a measure of energy?
Think about lifting an object (by pleasure or not): If you lift a mass of 1# over 12" , you have just exerted 1 ft-lb of work. If you release that object at the time of hitting the ground, the object will transmit to the ground 1 ft-lb of kinetic energy.
An example from our world: We tend to think of 12 ft-lbs airguns as "Nerf" guns, that's for the Brits. We like guns with multiples of that energy, what on Earth could you possibly do with "just 12 ft-lbs"?
Well, consider this:
You go bowling, and the bowling balls at your lanes are all 12#. The channel where the balls come out is a bit low, for aesthetic purposes, and the channel is located at 12" above the floor.
Your girlfriend has never been bowling, and she does not really know how to take the ball, you approach her when you see that she is using just two fingers. She cannot really lift the ball and the ball is perched at the edge of the rail.
When you get to her, he turns around to face you and the ball drops on your small toe.
You have just been hit by 12 ft-lbs., and I doubt you have the same concept about what "Just 12 ft-lbs" is.
;-)
So, we have established that Ft-lbs IS a unit that measures ENERGY.
But, what about CC-BAR? How could that be an energy unit?
Well, C-C stands for Cubic Centimeters, that means cm³, and it is = cm x cm x cm (length x width x breadth).
And BAR is a pressure, so it is a FORCE applied over an AREA, in unit terms, we can say that 1 kg of mass, resting on a square that is 1 cm per side = approx 1 BAR (0.98 to be precise).
And so, if we Multiply cm³ X kg/cm², we get kg-cm, which is a unit of energy/work because it is force exerted over a distance; exactly the same way that ft-lb is. Remember that in multplication, the order of the elements does not affect the result, so kg-cm is the same as cm-kg, or, within the different systems ft-lb.
Just a note here: ft-lb IS DIFFERENT from lb-ft, the former is a unit of energy, the latter is a unit of TORQUE.
We have now achieved the understanding that we are measuring a PROPORTION of energies:
The energy that goes out of the air tank/tube/bottle and the energy that comes out as a speeding pellet.
In THIS context, our "efficiency" measure is perfectly reasonable. AND since we are observing HOW MANY cc-bar's are needed to create ONE ft-lb at the muzzle, it makes for easy comparison across platforms.
Obviously, the LESS cc-bar's are used per ft-lb, the higher the efficiency of any given system is.
Remember: a LOW value is GOOD in this context.
Some writers want to go the "strict physics" way and divide the total energy output by the pressure excursion, but that does not take into account the volume of the chamber (tube/tank/bottle), so it is only useful as a comparison for THAT specific situation, and changes under this method can be tricky to interpret.
OK, so now, armed with our knowledge, let's take some examples from the real world.
My good friend Stephen Archer has just published an article on the tuning of the Micro-Strike, I do encourage you to read it in full. Since we cannot insert here any of the txts, figures, or charts, I will quote the numbers on two interesting tests that are summarized in this table:
As you can see, the efficiency of the system is pretty consistent whether the starting pressure is 300 BAR, or 207 BAR.
The difference between 33.9 and 34.0 can easily be explained by the rounding of some numbers.
These "settings" (hammer force strike and regulator pressure) then need around 34 cc-Bar/ft-lb
Along some discussions, some friends have pointed out that it is not too "scientific" to mix unit systems, and I agree, but (always a big but somewhere), if we were to unify the systems to either all metric, or all SAE, we would be doing a dis-service to the users.
¿Why? because current literature available already uses a MIXED system of units.
If you go to the Pyramyd AIR page corresponding to the Micro Strike, you see this:
The difference between 33.9 and 34.0 can easily be explained by the rounding of some numbers.
These "settings" (hammer force strike and regulator pressure) then need around 34 cc-Bar/ft-lb
Along some discussions, some friends have pointed out that it is not too "scientific" to mix unit systems, and I agree, but (always a big but somewhere), if we were to unify the systems to either all metric, or all SAE, we would be doing a dis-service to the users.
¿Why? because current literature available already uses a MIXED system of units.
If you go to the Pyramyd AIR page corresponding to the Micro Strike, you see this:
Sorry for the size, but if you want to consult the source page, its here
In any case, you can clearly see that the MOST COMMON data available for tank capacity is CC's and the most commonly available data for air pressure is in BAR
On top of that, I want to make it clear to everyone that we are not measuring the TRUE efficiency of our airguns, that would depend on the compressor used, the amount of electricity it draws for the compression of the air needed to fill the tank (we MAY do another entry regarding that), and the electricity itself is not the "PRIME ENERGY". In the US, where about 1/3->1/4 of the energy is still derived from coal, burned in electric plants that are relaitvely far away from the population centers, we would need to consider the effiiciency of the powerplant, then the transformation, then the transmission, then the transformation, then the distribution, and then the local losses of the energy grid from the post/vault transformer to the house.
How much is that? You would be ashamed of how badly we in the USA use our energy.
BUT, that is not the aim here, the aim here is to evaluate JUST THE LAST LEG of the energy between the PRIME energy and the pellet exiting at some given speed.
So, for THAT purpose I have chosen to use cc-bar/ft-lb to make it familiar to my esteemed readers.
If someone wants to burn me for "Scientific Heresy" my answer would be: "E puoi si muove".
;-)
Now, coming back to the Stephen Archer's article and the "Max Power" tune of the little carbine, here would be the numbers:
In any case, you can clearly see that the MOST COMMON data available for tank capacity is CC's and the most commonly available data for air pressure is in BAR
On top of that, I want to make it clear to everyone that we are not measuring the TRUE efficiency of our airguns, that would depend on the compressor used, the amount of electricity it draws for the compression of the air needed to fill the tank (we MAY do another entry regarding that), and the electricity itself is not the "PRIME ENERGY". In the US, where about 1/3->1/4 of the energy is still derived from coal, burned in electric plants that are relaitvely far away from the population centers, we would need to consider the effiiciency of the powerplant, then the transformation, then the transmission, then the transformation, then the distribution, and then the local losses of the energy grid from the post/vault transformer to the house.
How much is that? You would be ashamed of how badly we in the USA use our energy.
BUT, that is not the aim here, the aim here is to evaluate JUST THE LAST LEG of the energy between the PRIME energy and the pellet exiting at some given speed.
So, for THAT purpose I have chosen to use cc-bar/ft-lb to make it familiar to my esteemed readers.
If someone wants to burn me for "Scientific Heresy" my answer would be: "E puoi si muove".
;-)
Now, coming back to the Stephen Archer's article and the "Max Power" tune of the little carbine, here would be the numbers:
The efficiency is now about 36.4 cc-bar/ft-lb
IS that a BIG difference in respect to the 34?
Well, it is 10%. To each his own.
If we look at Steve Sciali's tune, we get a little different numbers:
IS that a BIG difference in respect to the 34?
Well, it is 10%. To each his own.
If we look at Steve Sciali's tune, we get a little different numbers:
There ARE "nuances" to these numbers. Basically the "definition" of a good shot.
In the above case, at shot #9 the carbine "dropped off" the regulator, shot #10 was a little low, and shot #11 was high. WHY? because once the regulator is off what is "backing" the valve is the full capacity of the tank, not only the regulated section.
This happens in ALL regulated guns, and is not exclusive to any specific architecture.
AND, if we are too strict, the efficiencies can go down to almost 40 cc-bar/ft-lb, but we need to understand and acommodate those "pushing the envelope".
So, NOW we have a solid ground to work on.
Regardless of the "tune" we can say with some certainty that the Micro Strike is a 34->38 cc-bar/ft-lb gun.
Hopefully, if we can agree, we can start following the different brands and models and see how things "shake up" with the "crowd sourcing of info".
It would be nice to have airgunners advocating for the airgunners as a group.
Now, do we have other examples?
Yes, one is the "Nano Strike" which is the entry preceding this one and that is what started pretty much this whole train of thought.
The other example at hand, in the comments of the above mentioned entry is Don Hansell's "Black Bandit"
and I quote:
"Volume measurements are approximately,
Plenum length is 5.700" x .745" I/S dia, from the top of the valve to the end of the pressure tube = 40.72 cc
minus the gage block, Gage thread length is 1.100" x 7.45" = 7.86 cc
which leaves a total length of 4.600 = 32.86 cc
Hole length in gage base is .710" x .435" diameter = 1.73 cc
Total plenum = 34.59 cc
If I figured it right??
I obtained these results, from the 177 cal w/10.5gr pellets, thru a 17-3/4" bbl, no reg in the pressure tube, OEM stock except for the Flat Wire SSG installed and set med setting for power.
I filled the gun to 1550psi (as close as I could get),
checked the gun gage to see where it read at,
then filled the gun to 3010psi (accurate gage),
then shot these 3 mags over the chrono, to get these mps/fps results/readings.
At the 219, 228, 229 reading is 1550 psi, (bottom reading per column)
any shot after this would have been below the 1550psi limit.
Shot in this order > meters per second > fps then fps
MPS------------------FPS
316- 320- 323 > 1037 -1050 -1054
304- 309- 311 > 997 - 1014 -1020
296- 299- 301 > 971 - 981 - 988
289- 282- 291 > 948 - 925 - 955
274- 280- 281 > 899 - 919 - 922
264- 267- 265 > 866 - 876 - 862
249- 253- 252 > 817 - 830 - 827
235- 239- 249 > 771 - 784 - 817
219-228- 229 > 719 - 748 - 751
316 = 1st shot >219 = 9th shot, = 271 mps/889 fps av
320 = 10th shot > 228 = 18th shot, = 275 mps/902fps av
323 = 19th shot > 229 = 27th shot, = 277 mps/909 fps av
for a total average of 274 mps for the 27 shots/899 fps av.
I had to fill the gun after each 9 shot string to keep uniform pressure."
So, given the data above, these are the numbers:
In the above case, at shot #9 the carbine "dropped off" the regulator, shot #10 was a little low, and shot #11 was high. WHY? because once the regulator is off what is "backing" the valve is the full capacity of the tank, not only the regulated section.
This happens in ALL regulated guns, and is not exclusive to any specific architecture.
AND, if we are too strict, the efficiencies can go down to almost 40 cc-bar/ft-lb, but we need to understand and acommodate those "pushing the envelope".
So, NOW we have a solid ground to work on.
Regardless of the "tune" we can say with some certainty that the Micro Strike is a 34->38 cc-bar/ft-lb gun.
Hopefully, if we can agree, we can start following the different brands and models and see how things "shake up" with the "crowd sourcing of info".
It would be nice to have airgunners advocating for the airgunners as a group.
Now, do we have other examples?
Yes, one is the "Nano Strike" which is the entry preceding this one and that is what started pretty much this whole train of thought.
The other example at hand, in the comments of the above mentioned entry is Don Hansell's "Black Bandit"
and I quote:
"Volume measurements are approximately,
Plenum length is 5.700" x .745" I/S dia, from the top of the valve to the end of the pressure tube = 40.72 cc
minus the gage block, Gage thread length is 1.100" x 7.45" = 7.86 cc
which leaves a total length of 4.600 = 32.86 cc
Hole length in gage base is .710" x .435" diameter = 1.73 cc
Total plenum = 34.59 cc
If I figured it right??
I obtained these results, from the 177 cal w/10.5gr pellets, thru a 17-3/4" bbl, no reg in the pressure tube, OEM stock except for the Flat Wire SSG installed and set med setting for power.
I filled the gun to 1550psi (as close as I could get),
checked the gun gage to see where it read at,
then filled the gun to 3010psi (accurate gage),
then shot these 3 mags over the chrono, to get these mps/fps results/readings.
At the 219, 228, 229 reading is 1550 psi, (bottom reading per column)
any shot after this would have been below the 1550psi limit.
Shot in this order > meters per second > fps then fps
MPS------------------FPS
316- 320- 323 > 1037 -1050 -1054
304- 309- 311 > 997 - 1014 -1020
296- 299- 301 > 971 - 981 - 988
289- 282- 291 > 948 - 925 - 955
274- 280- 281 > 899 - 919 - 922
264- 267- 265 > 866 - 876 - 862
249- 253- 252 > 817 - 830 - 827
235- 239- 249 > 771 - 784 - 817
219-228- 229 > 719 - 748 - 751
316 = 1st shot >219 = 9th shot, = 271 mps/889 fps av
320 = 10th shot > 228 = 18th shot, = 275 mps/902fps av
323 = 19th shot > 229 = 27th shot, = 277 mps/909 fps av
for a total average of 274 mps for the 27 shots/899 fps av.
I had to fill the gun after each 9 shot string to keep uniform pressure."
So, given the data above, these are the numbers:
Remember this is a NON-Regulated gun, but we still know the STARTING and ENDING pressures of the string. AND the number of shots in the string.
We also know the capacity of the tank in cc's and the output velocities for a pellet weight.
We have all the data needed to calculate the efficiency of the system.
Considering it is a non-regulated gun, I would say it is reasonably efficient.
The differences between Magazines 1, 2 and 3 are easily creditable to changes in temperature in the tank. Every time we refill a tank, it heats up, as we shoot it out it cools down, compressors and gauges also suffer differences due to temperatures.
As an old Physics teacher of mine used to say: "Everything is a thermometer".
Still, we do have a solid ground to compare platforms.
Effiiciencies in the "twenties" beat efficiencies in the "high thirties's / low forties".
And between an efficiency in the mid-teens to efficiencies in the high 30's, there is 100% difference.
Mentioning other guns, for example
- I just finished a DIANA Outlaw Gen "0", and it showed an efficiency of 12.3 cc-bar/ft-lb shooting at around 30 ft-lbs
- Or, a Stormrider, that made its appearance in the "SouthPaw Super Plinker" entry exhibits an efficiency of 10.2 cc-bar/ft-lb.shooting at 13-15 ft-lbs
- Or an Avenge "X" that yields an efficiency of 16.7 cc-bar/ft-lb at 52 ft-lbs at high power, or 16.4 cc-bar/ft-lb when shooting at 20 ft-lbs.
There are MANY factors affecting the efficiency of a PCP airgun: from barrel length to architecture of the barrel/tank connnection through the valve, to the hammer and valve itself, to the TP itself.
Each element needs dedication and care to optimize and maximize the "return for investment" in an airgun.
Whether you pump by hand, or use a compressor, the efficiency of your gun will dictate in large measure how much you can really enjoy it.
It's good to work hard to play hard, but it is even better to work smarter to play hard.
;-)
Simple fact of life.
Hope you enjoy the read, keep well and shoot straight!
HM
We also know the capacity of the tank in cc's and the output velocities for a pellet weight.
We have all the data needed to calculate the efficiency of the system.
Considering it is a non-regulated gun, I would say it is reasonably efficient.
The differences between Magazines 1, 2 and 3 are easily creditable to changes in temperature in the tank. Every time we refill a tank, it heats up, as we shoot it out it cools down, compressors and gauges also suffer differences due to temperatures.
As an old Physics teacher of mine used to say: "Everything is a thermometer".
Still, we do have a solid ground to compare platforms.
Effiiciencies in the "twenties" beat efficiencies in the "high thirties's / low forties".
And between an efficiency in the mid-teens to efficiencies in the high 30's, there is 100% difference.
Mentioning other guns, for example
- I just finished a DIANA Outlaw Gen "0", and it showed an efficiency of 12.3 cc-bar/ft-lb shooting at around 30 ft-lbs
- Or, a Stormrider, that made its appearance in the "SouthPaw Super Plinker" entry exhibits an efficiency of 10.2 cc-bar/ft-lb.shooting at 13-15 ft-lbs
- Or an Avenge "X" that yields an efficiency of 16.7 cc-bar/ft-lb at 52 ft-lbs at high power, or 16.4 cc-bar/ft-lb when shooting at 20 ft-lbs.
There are MANY factors affecting the efficiency of a PCP airgun: from barrel length to architecture of the barrel/tank connnection through the valve, to the hammer and valve itself, to the TP itself.
Each element needs dedication and care to optimize and maximize the "return for investment" in an airgun.
Whether you pump by hand, or use a compressor, the efficiency of your gun will dictate in large measure how much you can really enjoy it.
It's good to work hard to play hard, but it is even better to work smarter to play hard.
;-)
Simple fact of life.
Hope you enjoy the read, keep well and shoot straight!
HM
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