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mainspring characteristics?

Discussion in 'Anything Airgun Related' started by martin22, Sep 26, 2014.

  1. martin22

    martin22 Donator

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    just lately ive been trying to learn more about spring rifle tuning and ive come to realise theres a lot more to it than most realise and its something that probably takes years to fully understand

    ive home tuned a few rifles in the past (spit & polish or "dropped a kit in")with some good results but most of the time i send the rifle off but again the cost starts mounting,one thing im trying to get my head round is different springs for different results/firing cycles,i realise the only way to fully get your head round it is trial and error but that can quickly turn expensive

    the thing im looking at is what sort of difference do different strength/length springs make
    for example (and im randomly plucking figuers out the air here) but say a 3.1 gauge spring @ 250mm long compared to a 3.2 gauge spring @ 200mm long? presumably this would give somewhere around the same ft/ib but what sort of difference on the fireing cycle? (i understand the length difference would be a problem its just hyperthetical)

    then theres preload?

    again how does this effect the fireing cycle? is it mainly to do with piston bounce or is it more to do with useing different power bands of a spring (if that makes sense) again plucking figueres out the air for example,would a 3.1 gauge spring @ 250mm with 50mm preload give the same power as a 3.3 gauge @200mm with no preload ect and again the effect on the firing cycle and recoil?
    i understand theres a lot of other factors involved like swept volume,piston size/weight,transfer port ect but im just trying to get my head around springs at the min,unfortunatly i dont have a selection of various springs here although i wish i had as this is something i'd love to experiment with but if anyone with a bit of experiance can share there thoughts or if anyone has any usefull links it would be much appreciated
    im not very technical and sometimes laymans terms usually sink in faster with me but i am trying to get my head round it and learn without forking out too much money on the old trial and error synario
    thanks
     
    Last edited: Sep 26, 2014
  2. Tinbum

    Tinbum Delusions of adequacy

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    There are too many variables for specifics, but generally speaking a short, stiff spring will feel harsher than a long, soft spring. The "Ox" was the classic short stiffy, but to a certain extent that has been taken over by Titan, albeit with round wire so it doesn't grate away the internals. I prefer a softer "feel" with more predictable precoil and less piston bounce on the second phase.
     
  3. martin22

    martin22 Donator

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    yes that makes sense,ive owned and shot a good few tuned rifles im just trying to get to grips more with whats going off inside to produce a firing cycle that i find suits me,i know theres plenty of kits available and theres some good tuners out there but im keen to experiment myself and get a better understanding to find a set up thats custom to me and that ive done myself
    as you say theres a lot of factors involved i think it maybe just something i have to experiment with,a may be pm'ing you soon for another top hat and guide kit,and another enquiry for something else once ive worked out some measurements :up:
     
  4. Tinbum

    Tinbum Delusions of adequacy

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    No problem, experimenting is the key. It's very much a case of what you get used to, find a style and stick with it. (I wish I could!):rolleyes:
     
  5. Nickg

    Nickg Posting Addict

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    You will tailor your firing cycle far better by adjusting piston weight and pre load with the standard spring, Its also cheaper:) , I like very fast firing cycles, a lot of people think they are harsh, but in fact have shorter ,less violent recoil and surge and are easier to shoot accurately. It all depends on what you like.
     
  6. 177

    177 Donator

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    A lot of this is down to perception and, to a certain extent, bias - physics would suggest that you can't have a super-fast shot cycle without some penalties, but these can be somewhat mitigated by controlling the air cushion at the end of the shot cycle.

    It's a balancing act - I like a very soft and sedate firing gun. Some think thumpy is amazing (think V-Mach kit) and although it is a big step up from a plain factory gun it is nothing at all like a properly tuned gun.

    I actually like the factory mainspring on Weihrauch rifles a lot - with a bunch of internal tweaks, nips and tucks, it can be used to deliver an extremely polite shooting gun.

    I have shot some tuned rifles that have a very definite "Blimey, what just happened" shot cycle, while others produce a quiet and subtle 'thock' that immediately makes you suspect the gun is only pushing 4 or maybe 5 FPE when, in fact, it's around 11.2 with low single figure shot to shot consistency.

    The trouble is that there really isn't just one way of achieving the goal state and manufacturing anomalies can thoroughly pooch anyone's "system" :rolleyes:

    The more friction efficient you make the internals the more you have to be mindful of transfer port size, piston weight, piston seal sizing and other related factors, otherwise the gun will jump around like a fresh caught salmon :rolleyes:

    Basically, everything you do in a springer depends on other things being adjusted to create a balanced shot cycle. The fastest shot cycle I ever managed was pretty horrible to shoot by comparison with a gun I'd spent the time on to balance all the related factors out on.

    Feinwerkbau took a revolutionary approach by using a longer, softer spring in the 124/127 and trounced everything else out there in the process. There's a lot more to it than just that but the mainspring was crucial. TX rifles have almost no preload and yet they are surprisingly good right out of the box, mainly due to piston bearings and other stuff.

    I fooled with an HW95 earlier this year and ended up going into negative spring preload to keep it under power, due to the work I'd done elsewhere in the gun. Obviously that introduced a noticeable piston bounce, so the transfer port and other stuff had to be tweaked and then I undid about a third of what I'd done to that point to allow a factory mainspring with very little preload to shoot in a really nice, sedate shot cycle.

    Springs are one small part of a very big puzzle.

    Have fun tussling with your guns :)
     
  7. JD

    JD Donator

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    What sort of firing cycle are you aiming for Martin ? I prefer a Vmach style firing cycle myself.

    I see you've got a wanted add for a 77/97 probably better to use another action, rather than your freshly reblacked 77k for a test bed rifle. ; )
     
  8. martin22

    martin22 Donator

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    cheers for the replys fella's and sorry for my late reply,heads not been in it this weekend after some bad news regarding family but i did do a bit searching after i made the first post and made some notes and bookmarked a few good reads
    ive also been digging through some of my videos of rifles ive had tuned and tuned myself,once i get my head back in it ill get back on track with it
    cheers
     

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