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New Toy - I Have Wind...

Discussion in 'Anything Airgun Related' started by myiot, Dec 6, 2019.

  1. number10

    number10 Keyboard Hero

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    It may detect someone next to you doing a Horse and Cart ;)
     
  2. Ballisticboy

    Ballisticboy Busy Member

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    Unfortunately, 40 years of experience with people with engineering degrees has not given me a lot of confidence in their abilities whan it comes to aerodynamics or more especially the external ballistics of high spin rate projectiles.

    When a pellet leaves the muzzle the wind will produce an angular deflection to the trajectory. The energy of the pellet is irrelevant, any force will produce a change in the velocity vector. The force causing down wind drift is a component of the projectile drag, a function of pellet velocity squared and thus is a maximum very soon after pellet exit from the barrel when the pellet has turned into the relative airflow. It is the component of the drag force in the down wind direction which gives the angular deflection. When the pellet is down range the relative airflow may well be at a greater angle to the pellet direction of travel but the drag force and thus the down wind drift force will be much smaller due to the loss in velocity, but it may well still produce a greater angular change in the velocity vector. However, the distance over which that angular change in the velocity vector can act is much shorter. It is then simple geometry that an angular deflection close to the gun will give a greater drift than one close to the target which to me is entirely intuitive assuming you understand the mechanics of projectile wind drift.
    As for Chairgun, despite being a very simplistic model compared to the one I was using, it agrees with the results. Taking a .177 pellet a 5mph wind over 10 yards immediately next to the gun gives a deflection of just over 0.9 inches at a target at 50 yards where as a similar wind from 40 to 50 yards next to the target only gives a deflection of 0.1 inches.
    You can believe it or not, it does not change the facts.
     
    willo1962, pbrown and Jukebox like this.
  3. Jukebox

    Jukebox Better to burn out...than to fade away.

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  4. pbrown

    pbrown Super Moderator Staff Member Mod/Admin

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    Very interesting, thank you :up:
     
    Ballisticboy likes this.
  5. myiot

    myiot Engaging Member

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    Show us the maths. Still sounds like BS to me...
    What's the model you use? Your own?
    I said I'm not frightened by maths/physics.

    I'll believe you when you prove it rather than waffling. Surely something so profound has been published? Show us the reference
     
  6. Ballisticboy

    Ballisticboy Busy Member

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    I don't really care if you believe it or not. It has been explained as simply as I can to try to be helpful but, for someone who claims to be clever, you seem to have difficulty understanding basic concepts. If you don't believe me try it yourself in Chairgun assuming you know how to do it and that you believe that of course. The model used was an international six degree of freedom model, not mine, developed for gun launched projectiles as opposed to the simple three degree of freedom model used in Chairgun. I used that simply because I had it available.
    It is hardly "something so profound" very basic really and not of much interest except in unguided rockets. The mathematics can be found in any ballistic text such as the "Text book of ballistics and gunnery" or McCoy's book on external ballistics, though that still has some errors in it, so there is no point in boring the rest of the forum here trying to educate you in basic ballistic theory and the mechanics of gyroscopic stability.
    As I said I do not care if you believe me or not, life is to short to bother with clever people like yourself who can only resort to insults.
     
  7. charlie1969

    charlie1969 Engaging Member

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    :troll::ban:Think he's been sent here from the other forum to upset everyone on as many threads as possible
     
    willo1962 and myiot like this.
  8. myiot

    myiot Engaging Member

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    Oh dear, I didn't mean to upset you! I simply asked what model you were using. You can't tell us!?
    So what was the 'international six degree of freedom model' you were using? It has a name? Was it top secret?
    What were the 6 degrees?

    I've not insulted you at all (yet!) but I think you're a fraud...
     
  9. pbrown

    pbrown Super Moderator Staff Member Mod/Admin

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    Keep the discussion civil without resorting to personal insults please.
     
    The Robin likes this.
  10. nevadacowboy

    nevadacowboy Posting Addict

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    @Ballisticboy is a well respected member of this forum who gives us great insight into the dark arts of ballistics that us mere mortals often struggle to understand. This is proven by his numerous informed posts on the subject and I for one am grateful for his input.
     
  11. myiot

    myiot Engaging Member

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    It's not my intention to offend anyone! I might challenge one or two...
    That's the way I learn things. I don't believe everything I read.
     
  12. Ballisticboy

    Ballisticboy Busy Member

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    Think what you like I don't care and I don't think anyone else on here does either. If you really want to learn anything about external ballistics I suggest you study either of the two books I have already mentioned assuming you believe what is written down there as well. They will explain such basic concepts as to what constitutes a standard six degree of freedom trajectory model.

    If you think I am a fraud you should tell the army and navy since for nearly 40 years I was their source of ballistic data and later the MOD recognised expert on gun launched projectile external ballistics. Perhaps you should inform them that in your opinion all their ballistic data is rubbish. Funny how the shells seem to land where predicted though.
     
  13. myiot

    myiot Engaging Member

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    No worries. If you can't support your arguments with credible references ie published documents with your name on them, I simply don't believe you. You've declined to provide mathematical credence to support your argument, refer me to an obscure book & insult my intelligence!
    I have worked as a consultant to the MOD too so we may have common friends?
     
  14. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    We're all here to learn from each other and while a healthy skepticism / the desire for proof is entirely legit, it seems that you're going out of your way to be antagonistic and confrontational - which is not necessary, constructive, or welcome.

    Please ensure future posts remain respectful to other members, as required by forum rules.
     
  15. Popgun

    Popgun Donator

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    you will need to zero to 16m
     
  16. myiot

    myiot Engaging Member

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    I take your point. I would never wish to offend anyone.
    I'm a career academic (engineering) and it's in my nature to challenge.
    I'll take a look at Diplomacy 101. Not my greatest strength...

    Ian
     

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