Idea for a Kenitic Energy at impact measuring tool

[Willie14228]

Okay, so there is software and formulas to calculate the K.E of a round but the fact is those numbers are only for potential energy and are only numbers.
The idea that I have is to make a device that would allow a user to compare how hard a round hits at different yardage and or weights at the same yardage.
The device would need to give a reasonabley accurate measurement no matter what quadrant the impact of the round hits in the target. This limits the device to a trolley on steel rollers setting on a track system that is set at an angle. The reason for this is that anything on a swivel would have an issue with a leverage effect if the impact was made in the quadrant furthest from the swivel point.
So basically what happens is you shoot the target mounted on the trolley there is a sliding pointer that moves up with the trolley that marks the highest point the trolley traveled.
As long as the angle, and weight stays the same it should give accurate comparisons. While it may not actually show a number it would give you a visual representation of how hard a round hits the target, if your started at close range then worked through higher yards you could see how fast the K.E drops off.
What do you think?

 

[Guest]

Sounds like your standard ballistics tool used in the 17th, 18th and early 19th centuries.

At air rifle energies you could probably build that out of a block of hardwood and an old HO railroad system. I would expect you could get some pretty accurate measurements if you took your time and were precise enough in your measurements.

Rather than use a sliding index, just attach a pencil and use a roll of butcher paper. You will get less friction with the graphite tip moving over paper than trying to push a sliding bar. I like the idea of a cart vice a pendulum but here is one way to skin that cat:
http://hyperphysics.phy-astr.gsu.edu/hbase/Class/PhSciLab/balpen.html

Why not buy a cheap chronograph?

 

[Willie14228]

Chronograph is just a number and at 100 yards might be an expensive whoops I pulled that shot.
I guess I'm just interested in actually seeing what 400, or 500 kpe looks like

 

[Guest]

"Willie14228"Chronograph is just a number and at 100 yards might be an expensive whoops I pulled that shot.
I guess I'm just interested in actually seeing what 400, or 500 kpe looks like

What is kpe?

Yes, it would be an expensive oops.

 

[D4v0s]

I would think you might actually need to have some sort of putty on the trolly, you will want to capture all the energy you can get.

Might be interesting to see how far a 1 pound weight would move on a magnetic track. Would 50 fpe equate to 50 feet for the one pound block? Interesting.

 

[Alan]

I can't find the YouTube video, but I do remember seeing it a few years ago. The guy suspected a capped piece of pipe using fishing line. I don't remember the length of the line, but it doesn't matter. If you know the weight of the pipe, the length of the line, and the displacement (movement), math will give you the energy expended. Accuracy is perhaps a bit closer to the real number at some distance from the barrel, but the truth is, for any practical, airgun distance, the BC and velocity is all you really need. 


Read this: https://en.wikipedia.org/wiki/Ballistic_pendulum

 

[blackdiesel]

There is the Labradar that measures the speed of the projectile at all distances from muzzle to target. You can use this to calculate whatever ballistic equation you want.

 

[Guest]

Use chair gun app by Hawke it will do exactly what you need. http://www.hawkeoptics.com/chairgun.html

 

[Willie14228]

I do understand that there are apps and calculators that will give you the numbers. But that number IS Not, an actual representation of the impact but only a potential estimation.
There are many factors that will effect the actual energy that will be dumped into the target.
1. Bullet design, will it fragment, will it flower petal out, will it tumble all of these will
2. Type of body of target,
3. Angle of impact
4. Speed of projectile at impact will effect what number 1 will do at impact.
Don't misunderstand me numbers are great and all but actually seeing a visual effect will tell you a lot more

 

[nvelkhunter]

It appears there is some confusion regarding Force and Energy. These are not the same.
Force = Mass * Acceleration (or negative acceleration in the case of a projectile hit and object)
Energy Kinetic = 1/2 * Mass * Velocity^2

Force is highly dependent on how fast the projectile accelerates (again negative in this case). If a projectile hits a sponge versus hardened block of metal the force for each will be much different even thought the weight, shape and velocity were the same in both cases.

Kinetic Energy is defined and is relative to the velocity at which it is traveling at a particular point in time.

 

[Alan]

I agree with Nvelkhunter. Knowing the kinetic energy only gives you a potential maximum if indeed all of the energy was consumed. A passthrough (pellet exiting the target whatever it is) is evidence enough that not all of the kinetic energy was expended. Whether it is expended or not, has many more variables than the calculation for kinetic energy; compressibility of the pellet (hardness), pellet shape (round nose, flat nose, etc.), compressibility of the target (sinew, bone, skin, in any combination), just to name a few. All of these (and more) determination the force (expended kinetic energy). In a phrase... "It ain't so simple McGee!"

 

[nvelkhunter]

Check out the: Umarex Havox.

This projectile should transfer a lot more energy to your quarry than a standard solid nosed pellets.