Velocity from Audacity - special for Basu

[sathya.sniper]

This is really an interesting topic.
I always like to know the muzzle velocity of my rifle even if it not accurate i need to know it approx.
Just inorder to find out, is the tuning process going in the right way or not.

But i had lots of problem. Still i have some problems in finding the exact peaks of sound.
But after using BASU sir's excel sheet i could find more or less smooth values with a minimum deviation.

Would like to hear more info in this topic. Keep Going
Regards

[Suyash]

Dear Benne,
While going through the forum I saw your High Speed camera videos. You can use the camera for calculate the velocity and I think that it would be far more easier and accurate . I'm not sure if you've already done it.
Speed=distance ÷ time
So velocity can be calculated by shooting the pellets to a target at known distance. You can easily see the time taken by the pellet from leaving the muzzle and hitting the target using the high speed camera. Just divide the distance by the time. It would be interesting to compare the results with CC and audacity.

Regards!
Suyash

[bennedose]

No Suyash that camera and other cameras are not good enough. I have tried. Even with the camera that takes 1000 frames per second that I have - the pellet appears like a line, not a dot because at 150 meters per sec the pellet will have travelled 15 cm in 1/1000 second. So where do you start measuring from. It would be a different thing if I had a 25,000 frames per sec camera, but Chrony is cheaper.

[ganeshn]

No Suyash that camera and other cameras are not good enough. I have tried. Even with the camera that takes 1000 frames per second that I have - the pellet appears like a line, not a dot because at 150 meters per sec the pellet will have travelled 15 cm in 1/1000 second. So where do you start measuring from. It would be a different thing if I had a 25,000 frames per sec camera, but Chrony is cheaper.

This is exactly what u need the length of light streak and the duration of the sensor scan will give the speed.alternatively
1. use a strobe light like a DSLR flash at say fractional power the duration of the strobe is near 10 thousands of second, the length of steak left by the pellet will give you the speed.need to sync the trigger release with strobe, even that can be electronically done.
2.use a spinning disk with a slit infront of the lens, distance between two head/tail of streaks and angular speed will give the pellet speed.continuous light this time.
Need to keep the camera in B mode in both case.if you have access to strobe used in automobile garages to set camshaft timing of the engine try it it may work.

[Basu]

Dear ganeshn,
Your idea is great.....
Could you please start a fresh thread , depicting with some drawings.

Basu

[Suyash]

No Suyash that camera and other cameras are not good enough. I have tried. Even with the camera that takes 1000 frames per second that I have - the pellet appears like a line, not a dot because at 150 meters per sec the pellet will have travelled 15 cm in 1/1000 second. So where do you start measuring from. It would be a different thing if I had a 25,000 frames per sec camera, but Chrony is cheaper.

Dear benne
I think that a 1000 frame ps could do the job. Take the distance like 20m ~ and use a reactive target (like a balloon). I think that the projectile leaving the muzzle should be clearly visible. And the bullet hitting the balloon Will also give exact time... Use the time difference between them. I don't think we'll need to bother about the size of the pellet in slow motion as long as we can see the exact timing of projectile discharging and the balloon being hit.
By the way what is more expensive in India a 1000 frames p/s camera or a chrony? I'm not sure if my idea is economical.
Regards!
Suyash

[ganeshn]

Dear ganeshn,
Your idea is great.....
Could you please start a fresh thread , depicting with some drawings.

Basu

Surely Basuda will think of detailing it.

No Suyash that camera and other cameras are not good enough. I have tried. Even with the camera that takes 1000 frames per second that I have - the pellet appears like a line, not a dot because at 150 meters per sec the pellet will have travelled 15 cm in 1/1000 second. So where do you start measuring from. It would be a different thing if I had a 25,000 frames per sec camera, but Chrony is cheaper.

Dear benne
I think that a 1000 frame ps could do the job. Take the distance like 20m ~ and use a reactive target (like a balloon). I think that the projectile leaving the muzzle should be clearly visible. And the bullet hitting the balloon Will also give exact time... Use the time difference between them. I don't think we'll need to bother about the size of the pellet in slow motion as long as we can see the exact timing of projectile discharging and the balloon being hit.
By the way what is more expensive in India a 1000 frames p/s camera or a chrony? I'm not sure if my idea is economical.
Regards!
Suyash

The pellet hitting the ballon will surely give you the spatial position but time is still elusive in your scheme.

[bennedose]

1. use a strobe light like a DSLR flash at say fractional power the duration of the strobe is near 10 thousands of second, the length of steak left by the pellet will give you the speed.need to sync the trigger release with strobe, even that can be electronically done.
2.use a spinning disk with a slit infront of the lens, distance between two head/tail of streaks and angular speed will give the pellet speed.continuous light this time.
Need to keep the camera in B mode in both case.if you have access to strobe used in automobile garages to set camshaft timing of the engine try it it may work.

Nice idea. The spinning disc is something I wanted to do - actually I wanted to try spinning mirror. But the real problem is ambient light. You need extremely bright ambient lighting - which for me means doing all this in open sunlight. Setting up the apparatus in the open is less easy than one might think.

The strobe thing is interesting - but one has to be absolutely certain that the strobe flash is accurate because the velocity measuremet in this case is totally dependent on the accuracy of strobe flash.

Another thing I wanted to do was to simply get an image of the "streak" of the pellet at 1000 fps in front of a white background where centimeters were marked in high contrast ink. Again the problem is lighting - but it is doable if I can get rid of the inertia on a hot summer day. But I found audacity and Chrono connect more convenient and with a Chrony - all this will simply become fun and games to be tried "at some stage"

[bennedose]

Dear benne
I think that a 1000 frame ps could do the job. Take the distance like 20m ~ and use a reactive target (like a balloon). I think that the projectile leaving the muzzle should be clearly visible. And the bullet hitting the balloon Will also give exact time... Use the time difference between them. I don't think we'll need to bother about the size of the pellet in slow motion as long as we can see the exact timing of projectile discharging and the balloon being hit.
By the way what is more expensive in India a 1000 frames p/s camera or a chrony? I'm not sure if my idea is economical.
Regards!
Suyash

Chrony is cheaper.

The least expensive 1000 fps Camera I could afford to import via "brother's luggage" route was the Casio Exilim which was just over 200 US$ when I bought it. Chrony is half that price. Unfortunately brother's luggage route is useless for importing air rifles or I would have done that rather than getting all these spare tool items like camera and chrony

Your idea is nice - I will definitely try it for the fun of it. 20 meters is too far but it may be possible at 5 meters. It will need bright sunlight and a plain white or black background with distance markings because it is difficult to predict how far outside the muzzle the pellet will first be seen. I am expecting an error of about 15-30 cm and at 5 meters that will give an error of less than 10%

But you idea may be implementable even with an ordinary video camera. Modern cameras can "freeze" a pellet in mid air especially when filming in the "sports/motion" mode. But you will need
1. Bright sunlight
2. Plain black/white background with a scale/distance clearly marked because you will never know exactly where the frozen pellet will be seen

In fact I started experimenting with this stuff long before I joined IFG. My earliest experiments used an ordinary camera flash gun that I set up in such a way that it would flash as soon as the pellet passed a particular point. I did this by taking wires from the contacts of the flash gun and connecting them to two aluminium foil sheets placed very close together. The pellet would pierce through the first sheet and make contact with the second sheet causing the flash to go off. But even a 1/200 second flash is too toooooo slow. And in those days there was only photo film - not digi cameras so I could not find out the result until the film was developed.

More recently I tried the multiple frames method with digital cameras. Nothing worked consistently until I bought the Casio Exilim.

[brihacharan]

VELOCITY
In my considered opinion ‘Velocity’ has been the “Bone of Contention” of AR shooters across the world.

We all know too well that even reputed manufacturers of AR spike their claim by using light weight pellets ….for what reason? May be to exaggerate the AR’s capability or performance to maximize the sale of their products!

But the ground realities tell us a different story…

While a reasonably high velocity is desirable, the factors that affect in achieving it are worth looking into & maybe they arise from the inherent inadequacies of an AR…

The variables are too many –
POWER SOURCE:
•Spring- Its metallurgical composition, tenacity, resilience, no. of coils, OD of its coils, compressibility….
•Piston -Its length, weight, ID & OD…
•Top hat & Rear Guide – Quality & type of material, tolerance in fitment in spring, dimension…
•Seal – Quality, material, compressibility, efficiency….
•Lube – Mobility, tackiness, stability, friction coefficient….

BARREL:
Its length, rifling (twist), condition, fitment with breech….

BREECH SEAL:
Its quality of material, fitment, retention…

PELLET:
Its shape, configuration, composition, fitment in the breech, propensity to confront aero-dynamics….

AMBIANCE:
Hot, humid, windy…

Now coming to ‘Velocity’ which velocity are we considering – Muzzle, In-flight or Terminal? Muzzle velocity will be of no consequence if any of the above mentioned factors play a role in minimizing it….

The question now arises is that – Would one compromise ‘Smoothness’ & ‘Accuracy’ to gain ‘Velocity’???

It all boils down to understanding & evaluating the AR’s performance, its deficiencies and then identify them and go about experimenting through ‘tuning’ to arrive at a particular state of performance, when the AR will begin to shoot with minimal vibration, reduced lock-time & be accurate.

Now sit back & think – are the methods, technology / equipment etc. put to good use or are they only part of academic exercises that lead to a good debate, with no conclusive / applicable solution to upgrade / enhance ‘Velocity’???

Here’s an article (with reference & source) that may interest those obsessed with ‘Velocity’

What do advertised air-gun velocity numbers mean?
Posted on February 14, 2013 by B.B. Pelletier a.k.a. Tom Gaylord
www.pyramydair.com/.../2013/.../what-do ... elocity-nu

Air-guns are usually advertised with their expected top velocities. What do those numbers represent? Today, I’ll attempt to explain this as clearly as I can.

THE NUMBERS ARE JUST LIES!
Let’s get this one out of the way first because it seems to be the prevailing belief that advertised velocities are nothing but lies put forth by marketing departments to sell more guns. There’s some truth to this belief, but it isn’t 100 percent by any means. Here’s what’s going on with the lies.

In the 1970s, spring-piston air rifles broke the 800 fps. “barrier” for the first time. Three guns the BSF S55/60/70, the Diana 45 and the FWB 124 all topped 800 fps in .177 caliber…and the HW 35 came very close to 800. That started the velocity wars that are still with us today. In 1981/82, the Beeman R1, which was also produced as the HW 80, hit 940 fps in .177. A year later, it was hitting 1,000 fps right out of the box, and that became the new standard for magnum air-guns.

A couple years after that, Diana offered 1,100 f.p.s. with their sidelever models 48 and 52, and from that point on it was necessary to go even faster to gain recognition in the air rifle class. A thousand feet per second was now considered the lowest velocity a magnum air-gun should achieve in .177 caliber.

Then, Gamo upped the ante with their 1200 Hunter Magnum that became the 1250 a year after it was introduced. This was in the late 1990s, and I was writing The Air-gun Letter, so I obtained a 1250 from Gamo and tested it for myself. To my utter surprise, that test rifle achieved 1,257 f.p.s. with an RWS Hobby pellet & I thought the game was finally over. Boy! was I mistaken.

Within five years, air rifles started hitting the market with claims of over1,300 f.p.s. And then they bumped up-to 1,350 f.p.s. You could almost hear the various marketing departments discussing what they had to say in order to sell their next new magnum air rifle. But when I tested these guns, they fell short of their advertised marks. I was not quiet about that fact; but when the box on the store shelf says one thing and I say another, guess which one people believe?

The numbers kept right on climbing — up past 1,400 f.p.s., then 1,500 f.p.s. and finally stopping at 1,650 f.p.s. I’ve also tested many of these newer rifles; and while they often do achieve velocities that used to be impossible, like over 1,300 f.p.s., none has ever hit 1,500 f.p.s. without some kind of fuel-air explosion being involved. The fastest velocity I’ve ever recorded from a spring-piston air rifle was just at or below 1,400 f.p.s., and one person reported he had achieved a legitimate velocity of 1,425 f.p.s. I’m talking only about spring-piston air rifles now, because a .177 AirForce Condor has hit 1,486 f.p.s. in one of my tests.

NON-LEAD PELLETS
While all these velocity claims were stacking up, the market was also flooded with lead-free pellets. Being lighter than lead pellets, these pellets went faster at the muzzle. The fact that they could not carry that velocity very far downrange was lost on the majority of people. One ambulance-chaser “expert” witness in a wrongful air-gun death lawsuit went so far as to compare a magnum air rifle pellet to a .22 rim fire bullet fired from a handgun. He “demonstrated” on television that the air-gun was faster than the firearm with no mention of the effects of a lightweight pellet compared to a 40-grain bullet. Well, a neutrino travels at nearly the speed of light and passes through the earth un-resisted; but since it has almost no mass, it doesn’t do any damage. Velocity alone means little.

COMPANY VELOCITY CRITERIA
Some air-gun manufacturers categorize their guns by the velocity they produce. Daisy is one that does. They have youth products separate from their Powerline products. They recommend their Powerline products for shooters 16 years and older. I searched the Daisy website looking for the velocity break between a youth gun and a Powerline gun but didn’t find a number. But looking at what the Powerline models deliver, it looks like any gun capable of shooting faster than 600 f.p.s

WHAT DOES THIS MEAN TO AN AIR-GUNNER?
An air-gunner has no way of knowing the meaning of the velocity number that’s given with a particular air-gun. It could be for bragging rights, or it could be the fastest velocity the company engineers were able to obtain from the gun under controlled conditions.
They could be using the number to sell more guns to uneducated shooters, or they could be using it to segregate their products for sales to different jurisdictions.

AND THE ANSWER IS…
There is no one answer!!! Air-gun velocity is a complex topic that’s driven by forces both within and outside the company making the guns. THIS IS WHERE THE BUDDING AIR-GUNNER HAS TO BECOME A THOUGHTFUL RESEARCHER WHEN LOOKING FOR A CERTAIN GUN.

Experience is the best guide when it comes to this topic. With experience, you’ll know what the limitations are, which companies do what with their numbers and so on. But never think for a moment that all published velocities are correct!
Briha

[Suyash]

Dear briha Ji
Very good article indeed BUT I think that here in India hardly any manufacturer ( except preciole) ' formally' mentions the velocity.... If you bargain hard with the seller for the velocity , he'll make a wild guess . in my case I called the seller several times after he said ' 450 fps with a 12 gr pellet ' . I thought that it was a bit less. I even asked the question about 450 fps in the forum when someone rightly said How does he know if it's 400 fps or 500 fps? Now when I measured the velocity it turned out to be 530 fps .
I think that there is much need to improve the sector