Accelerometer + Gun

047

Chris Suprock attached a accelerometer to his Mini-14 to analyze what happens before and after the shot.

[Hat Tip: Hackaday]

[ Many thanks to Callum for emailing us the link. ]

Related

Steve Johnson

Founder and Dictator-In-Chief of TFB. A passionate gun owner, a shooting enthusiast and totally tacti-uncool. Favorite first date location: any gun range. Steve can be contacted here.


Advertisement

  • http://harqueb.us harqueb.us

    Holy chicken wing Batman!

    • Bsr

      Hahahahaahahah +1 thats funny, thats why he cant shoot right and needs all that fancy smancy stuff to see why he cant shoot

  • neez

    Why does he have it attached to the back? He would probably get a better picture of what’s going on if he attached it more towards the muzzle.

  • 6677

    He annoys me. Its zed not zee, it always has been zed and everyone else says zed. What did they teach him in school?

    • Mouldy Squid

      Americans always say “zee”. I don’t know why, but they do. Pretty much everyone else who speaks English natively pronounces it “zed”.

    • RocketScientist

      He’s an American (you might have been able to tell by the accent). He was taught the same pronunciation we were ALL taught at school here in America: Zee. Rhymes with Cee (C) , Dee (D) , Eee (E), Gee (G), Pee (P), Tee (T), and Vee (V).

    • Mike Knox

      Thre’s more than one english in the world. I’m wondering why you didn’t know that..

  • Doesitmatter?

    Good theoretical analysis tool. But what would be real world application? What I can see is perhaps to investigate interaction between gun and body (and this is what he seem to to be mainly after). Perhaps, it can lead to some sort of pad in-between which would lead to better control. Would it be attached to jacket or to the gun? Otherwise, the gun will always remain what it is; it has got its own mind.

    By the way, the plot seem to show negative (along with positive) accelerations. I do not see it happening in reality. Can author explain? Thanks.

    • TATim

      Why can’t you see negative acceleration happening in reality?

      Acceleration is a vector quantity with a magnitude *and* a direction. If I had to guess I would suggest the negative quantity is a change in direction of the acceleration vector (i.e. gun accelerating upwards then accelerating downwards once it reaches the top of the motion).

      • Doesitmatter?

        Thanks for contribution to my understanding. My thought is (and also with help of RS above) that this is merely instrumentation setup issue. It is conceivable that the acceleration will be much stronger (in extremely short period of time, say in couple of milliseconds) than de-celeration. This may last 10, 20x or even more depending on rate of restitution of backing material. So, the issues of de-celeration (as -a value) is perfectly understood. What caught my attention is that in chart it happens seemingly in immediate following and in about same rate. This is what I do not see as realistic.

  • RocketScientist

    He’s on the right track, but as someone who does vibration testing/analysis for a living, he needs to improve his setup somewhat. Looks like a lot of high-frequency noise in his data (to be expected), could probably benefit from some bandpass filtering to clean it up if he’s more interested in the gross motion/acceleration (like recoil etc.). Or if he’s looking at the very transient high-speed shock events (lock/action events, firing, etc) he probably needs a higher-speed data recorder than the laptop and cheap USB accels he’s using (would also benefit from moving the triad to mount somewhere on the receiver itself in that case,to eliminate whatever damping/resonances/frequency response the stock itself provides).

    I would really like to get my hands on that raw data and do a Fast Fourier Transform or something on it to get it in frequency domain. PSD (power spectral density) plots can tell a lot more about these sorts of things than the time-history data he shows. Or maybe even SRS (shock response spectrum) or PVSS (psuedo-velocity shock spectrum) like we use to analyze pyro-shock testing. I would imagine a gunshot and a pyro-shock profile have a lot in common (very transient event, probably very high instantaneous accelerations, etc).

    As for the comments about negative accelerations, that is to be expected. If accelerations were all positive, that would indicate that when the gun fired, it was pushed in the ‘positive’ direction and never stopped… it would still be moving now. If the net velocity after the shock event was zero (meaning the gun came to a rest and stopped moving, as we would expect) this would imply the acceleration would have to be negative at some point. Along the same lines, if we assume the net displacement was zero or near zero (as would be expected, meaning after the shot the gun is returned to about the same position it was fired in, back on target) there would be period of negative velocity as well. Otherwise the gun would end up considerably further away in the ‘positive direction’ (like we would see in a free-recoil test setup). Velocity is the time-rate-of-change of position (displacement), acceleration is the time-rate-of-change of velocity and Jerk is the time-rate of-change of acceleration (and very rarely used). If you take the derivative 3 steps further, the quantities are refereed to as Snap, Crackle and Pop (like the guys from the Rice Crispies box)… see, engineers DO have a sense of humor.

    Also: instrumenting and directly measuring is not a good “theoretical tool”, it is a good empirical real-world data gathering tool. A ‘theoretical tool’ would be like developing a FEM model of the gun and stock, defining estimated boundary conditions and modeling the gun without ever firing it. Gluing a triad to the stock is as ‘real-world’ as it gets.

  • Randel

    we live in an age of Geeks with guns, it was bound to happen.
    reminds of a line I read,
    You only need to know 2 things,
    Is he/she a good shot?,
    Will they be shooting at you or at your enemy?
    The rest is just talk while we wait to start the shooting.

    • RocketScientist

      I think its a fair statement that we’ve always had nerds with us in the firearms industry. Anyone who thinks John M. Browning and Eugene Stoner weren’t nerds need to look at their history. You don’t get 130 or so patents (the first in your early 20s) and design your first working firearm at 13 without being a nerd. Plus look at a picture of Browning: tall, gawky, scrawny… looks like something out of central casting for Revenge of the Nerds V :). The tools may have changed, but in his day a set of calipers and a slide rule were probably as ‘nerdy’ at the range as this guy’s accelerometer triad and a laptop.

    • Blackhawk2001

      OOOH! A paraphrase from Cantra yos’Phelium! I like it!

  • Al T.

    BZ! As a firearms coach, having the ability to stick a bracelet on a shooters wrist for diagnosis would be money well spent (as apparently shown towards the end of the video). I would think that institutional organizations (academies) would fall all over themselves to get this tool.