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ONE FOR THE TUNERS

Discussion in 'Anything Airgun Related' started by DUNKS, Jan 13, 2014.

  1. DUNKS

    DUNKS Big Poster

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    Ok we all know we should polish the ends of our springs in spring guns. I have even read of folk doing it on hammer springs on PCPs.
    WHY DO WE DO THIS? The obvious answer is that the ends of the spring turn when the spring is compressed and again when the pressure is released. Polished ends aid this.
    BUT DO THEY TURN? I am not asking the "well I think so brigade". Do you actually know that they do?:confused:
    I am pretty sure that vehicle suspension ones don't. They sit in a nice little groove.
    I know that the cropped Wheihrauch springs do chew lumps out of your gun but is this the turning action or just them bouncing about.
    Or have I got it all wrong and we polish cos we aint got anything better to do?:D
     
  2. JD

    JD Donator

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    The torque twist in a springer, tells you the springs trying to turn but in failing to do so, turns the rifle to the left or right.

    I've only felt springers twist to the right though ?
     
  3. Dunkman

    Dunkman Posting Addict

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    There is a HUGE misconception that as the spring unwinds it induces torgue into the action of the gun and tries to rotate it about its longitudinal axis - It can't. The spring is not held at either end so it cannot impart any torque force into the rifle. Lets now imagine the spring is held at either end, it still cannot induce a torque force into the gun since both ends are fixed and the piston cannot rotate since it is held in line via the cocking slot.

    If you want to be very scientific about a spring, it is a steel rod that is in torsion (twisting) along it's length. As it comprssses, the steel is twisted ever so slightly along its length and untwists when decompressed. A spring does have a tiny amount of twisting force when compressed or decompressed but this is negligible and as you say, car coil springs don't turn when compressed. If they did, the car would want to steer left or right as the spring tries to twist the suspension strut it is fixed to. Of note is the fact that car suspension springs are not handed, ie, the coils on both left and right hand springs are the same. If there was any twisting forces, manufacturers would make LH & RH springs with opposite coil winds to counteract the force. They don't so this says a lot!!.

    On spring guns you can see chatter marks inside the piston or on the end of the guide but this is the spring jumping around after as it is fired and the ends (if unfinished) are gouging into the metal. The ends of the spring want to be smoothly finished with no rough edges but as for polishing the ends, if it makes the person happy then polish away but a good finish and a dab of Moly on the ends is all that is needed.

    Lots of urban myths in air-gunning...........
     
    Last edited: Jan 13, 2014
  4. Darren Petts

    Darren Petts Temporarily Alive

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    The spring is held at both ends via friction. This friction is overcome as the gun fires and one or both ends rotate slightly. The spring can not impart torque to the gun though because opposite ends of the spring are working in opposite directions. This friction is overcome in a juddering manner causing vibrations in the spring which are unwelcome. Delrin top hats and guides are used to lower this friction to a minimum and smooth the vibrations to as little as possible. Easing out the juddering allows the spring to perform at it's most efficient.
     
  5. JD

    JD Donator

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    You've never had a spring rifle twist in your hands then Darren ?
     
    Last edited: Jan 14, 2014
  6. Darren Petts

    Darren Petts Temporarily Alive

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    Never. Had them twang, kick like a mule, vibrate like a bad 'un, shoot silkily and anything in between but never experienced rotation.
     
  7. Accuspell

    Accuspell Pro Poster

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    All reasons why a gas ram is so much better! :D
     
  8. wonky donky

    wonky donky Donator

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    If you mark a piston in an air rifle such as a Diana where the piston is free to rotate you will find the piston is forced to rotate by the spring, every so many shots the piston does one complete turn. On a rifle where the piston has to follow a cocking slot a twist is imparted to the rifle hence the need for top hats.
    Venom used to fit a screw into the rear of the piston to stop it rotating on the Lazerglide HW80 otherwise the piston would rotate & the latch rod would not be able to engage the trigger. I do the same because the spring does twist & gradually rotate the piston, I know this from first hand experience.

    As for left & right handed springs, manufacturers such as Feinwerkbau make them as standard for the 300s, Walther, for the older LGV target rifle, even BSA used to make left & right hand spring sets. I have some of each here. The reason most manufacturers don't make them is cost nothing more!
     
    Last edited: Jan 14, 2014
  9. mark.177

    mark.177 Donator

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    heres my thoughts.... maybe the spring doesnt rotate? this is something i agree with. i have noticed with spring air guns some twisting and used to believe it was the spring rotating in the cylinder but now im not so sure? as a spring is compressed neither end rotates but you do notice some buckling as it does when the coils are let fly upon firing there maybe is some slight sideways kicking out from the centre coils and being high up on top the stock in the cylinder appears as though the rifle is twisting?
    have been playing with smaller springs this morning and after marking both ends and compressing on a tube i see no rotation at either end... but did notice the coils kicking out in the centre as compressed if any play
     
  10. DUNKS

    DUNKS Big Poster

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    I agree. As for the pistons slowly turning I think that if the spring touches the inside of the piston it will attempt to turn it as the coils are at an angle.
     
  11. Dunkman

    Dunkman Posting Addict

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    The spring cannot impart torque (twist) into a rifle because of the simple fact that both ends of the spring are inside the rifle therefore EVEN if the spring does twist, it is captive within the mechanism that you are holding ad has nothing to act against.

    What some people may be experiencing if the spring is not very well supported by a guide and a sleeve is the spring then it will bounce around inside the cylinder as it rapidly decompresses and this bounce may make the rifle jump around (randomly) and make the gun 'jumpy'.

    Here is an uncompressed spring

    03-13-12-02-mainspring-in-tool.jpg

    The same spring compressed but unsupported. Notice how it wants to bend out of alignment. Now imagine what happens when a spring in that state is rapidly decompressed and allowed to flap and jump around like Zebedee on speed.

    03-13-12-03-mainspring-nearly-compressed.jpg
     
  12. bigtoe

    bigtoe Donator

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    Whether the spring exerts force to twist or not, pistons rotate. My sleeved hw80 has a free to rotate piston and it rotates 360deg ever 12 shots or so..

    More often then not the rear guide is tight, this holds the spring firm and often fixed at the trigger end, whether this makes the piston rotate I will let you decide, i just know they do.
     
  13. JD

    JD Donator

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    It has to be asked,

    Why do we fit slip washers, if the spring remains free from rotation ?
     
  14. Dunkman

    Dunkman Posting Addict

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    Out of habit. No harm in doing it and they do prevent the inside of the piston or end of the guide getting chewed up by the spring chattering.
     
  15. sharpsman

    sharpsman Big Poster

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    If there is no twist how come a piston will turn then ?,also i have experienced the feeling of the rifle trying to twist to the right as someone else has in an earlier comment.
     
  16. Dunkman

    Dunkman Posting Addict

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    The sensation of twisting is most likely the spring rattling away inside the cylinder if it is not fully supported by decent guides. As I said before, the spring CANNOT impart a torque re-action to the rifle since both ends are inside the rifle that you are holding.
     
  17. JD

    JD Donator

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    Chattering,

    Idle talk, one who talks or chatters incessantly.

    Springs rotate, not chatter.
     
  18. sharpsman

    sharpsman Big Poster

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    How come the piston turns then? it might not be much but they do turn slightly with each shot-obviously this can only happen if the piston is free to rotate such as tx's ect.
     
  19. Dunkman

    Dunkman Posting Addict

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    In engineering, Chatter marks are small indentations cuased by 'chatter' between two objects. You can sometimes see chatter marks on the inside of pistons or the base of spring guides if the spring ends are a bit rough. It's the spring rebounding and coming away from the contact surface during the firing cycle and when it eventualy contacts the surface again, it hammers small indentations (chatter marks) onto the surface.

    chatter mark also chat·ter·mark (chtr-märk)
    n.
    1. A riblike marking on wood or metal, caused by vibration of a cutting tool

    http://www.thefreedictionary.com/chatter+mark
     
  20. Dunkman

    Dunkman Posting Addict

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    Exactly, the piston may turn a small amount each time but that is why any twisting force is transferred to another item, in this case the piston, and not the rifle itself.

    OK, imagine it another way. For every force there is an equal and opposite force. So in the case of the small amount of twisting force a spring will exert when compressed/extended (and it is a tiny amount, really small) that twisting force happens at BOTH ends of the spring. One end will want to rotate clockwise, the other end anti clockwise. The force is the same therefore since both ends are inside the gun, one force cancels out the other.
     
    Last edited: Jan 14, 2014

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