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Bsa Spitfire Service

Discussion in 'Technical' started by cooper_dan, Sep 30, 2019.

  1. cooper_dan

    cooper_dan Busy Member

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    Made a bit more progress on the spitfire today. It's 90% apart now, but I've been interrupted to do the weekly shop :rolleyes:

    Looks like the seal kit from knibbs doesn't include everything, and the knock open seal has cracked. Is this the excuse I need to get a mini lathe....

    IMG_20190930_193514051.jpg
     
    phil.m and Paul Chell like this.
  2. the logun-ator

    the logun-ator "can i,? wey aye man!"

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    been there,done that
    yea i made a new valve seal as well
    didnt buy a oring kit,just measured the originals and ordered 10 of each
    i hope you measured/took note of where/how high/how many turns on the rear of the exhaust valve?
     
  3. cooper_dan

    cooper_dan Busy Member

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    Measured everything, BUT bought this cheap as a leaking rifle/potentially failed repair. Based on the scratches on the bluing where the cylinder was clamped to remove the breech, it may have been open before, and not very carefully....
     
  4. Deejayuu

    Deejayuu Donator

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    Great thread. Watching/listening with interest.
     
  5. cooper_dan

    cooper_dan Busy Member

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    Need a bit of help!

    There is a steel sleeve that's a light press fit into the fill probe body bit (steel sleeve is the smaller black part in the picture). This is part of the sealing between the main pressure cylinder and the hammer.
    Anyway the parts diagram i have shows an o-ring and a washer between this and the filling body. Mine has an o-ring but no washer....
    Should there be one? And what size should it be?
    @the logun-ator @Paul Chell did yours have a washer behind this pressed in part?
    IMG_20191002_192639691.jpg
     
  6. cooper_dan

    cooper_dan Busy Member

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    Got some CAD done today. Main cylinder, breech, front valve seat, and filling/valve stem body done.
    Might try to get the valving parts finished tonight. Possibly hammer and anti-bounce parts tomorrow.
    Looking at this image, I think I need to change the colour of the o-rings to make them visible.
    SPITFIRE_1.PNG
     
    Deejayuu likes this.
  7. cooper_dan

    cooper_dan Busy Member

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    Some more BSA Spitfire internals. Now the anti-bounce assembly has been added behind the hammer*.

    *Generally with PCP's the term 'hammer' is used to refer to the moving weight which hits the knock open valve. In the case of this BSA (parts diagram and owners manual), the hammer is actually the part which gets hit, i.e the bronze coloured part in this image.
    The moving part is called the 'striker' (not shown).

    In this assembly the two parts are separated by the anti-bounce assembly. The lighter blue component can move when hit with the full force of the striker (i.e when firing). However after the initial strike, once it has been reset, there is not enough energy to move it again. Therefore the main valve is opened once, and once only. The amount of force required is determined by the spring underneath the ball bearing.

    spitfire_5.PNG
     
    Deejayuu likes this.
  8. El Caro

    El Caro Posting Addict

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    There is a great deal of info about the Spitfire on the JB fanpage. For instance the striker is in two parts. The striker spring is very strong but with little or no pre-load. The two part striker is launched at the back of the anti-bounce when the trigger is pulled boosting its efficiency. Way ahead of its time with many, even now, advanced features
    I edit the JB fanpage and publish info sent to me. You have to scroll down the pages to find what you are looking for. Many photos too. James.
     
    cooper_dan likes this.
  9. cooper_dan

    cooper_dan Busy Member

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    Thanks I'll have a look
     
    El Caro likes this.
  10. El Caro

    El Caro Posting Addict

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    The Spitfire anti-bounce device was used earlier in the SuperTen with a slightly weaker spring behind the ball. JB chose the patented device from several he had developed previously. Its main purpose in the S10 was for the rifle to pass the US drop tests. BSA didnt want to take the easy route and class it as a match rifle so avoiding the test. The bonus was that it increased shot count by not wasting air.
    Its main purpose with the Spitfire was to save air with the unique partially balanced valve and striker system:)
     
    cooper_dan likes this.
  11. cooper_dan

    cooper_dan Busy Member

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    Striker assembly now added. There's quite a lot going on in the little Spitfire!

    spitfire_6.PNG
     
    BARNEY20 and norman like this.

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