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Thread: Converting the Webley Senior from a piston ring to a leather seal?

  1. #16
    eyebull's Avatar
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    Quote Originally Posted by Bruno27 View Post
    Hi

    I am very interested by this thread as I will have to refurb my junior. Junior has a leather piston seal but the breech seal is my main concern.

    For my curiosity, I have a few questions for you guys:

    What does 'PB ring' stands for?
    What is the material of this ring?
    Beryllium copper?

    Many thanks
    'Phosphor Bronze', answers both questions I think

    I must admit to always being very keen on the concept of the PB piston seal. As I understand it the reason it was not used in future Webleys was due to cost, rather than leather seals being an improvement.
    IIRC the FWB65 uses a PB piston ring, and that was not a 'cheap', or half-arsed, pistol.

    They are meant to have an extremely long shelf life, I seem to recall figures like a half million, or a million shot cycles bandied about, particularly with reference to the FWB65. For that reason I'd be inclined to keep it in situ...
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    Quote Originally Posted by eyebull View Post
    'Phosphor Bronze', answers both questions I think

    I must admit to always being very keen on the concept of the PB piston seal. As I understand it the reason it was not used in future Webleys was due to cost, rather than leather seals being an improvement.
    IIRC the FWB65 uses a PB piston ring, and that was not a 'cheap', or half-arsed, pistol.

    They are meant to have an extremely long shelf life, I seem to recall figures like a half million, or a million shot cycles bandied about, particularly with reference to the FWB65. For that reason I'd be inclined to keep it in situ...
    Agree with that 100%.
    The FWB 300 rifle uses a split ring as well, though I am sure steel ones with a stepped split section (higher performing) are advertised as non original replacements.

    I think there is absolutely nothing that a half decent split ring cannot handle in airgun cylinder pressures since they have been used for ages in high compression turbo-charged diesel engines and last many years in the harshest compression cycle one can imagine.

    I think a reasonably competent person with a lathe can turn a few rings effortlessly if the cylinder bore is still true and the piston groove/cylinder dimensions are known. I would hate to loose more of what little power these fine pistols make by fitting leather washers.

  3. #18
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    Quote Originally Posted by dvd View Post
    Agree with that 100%.
    The FWB 300 rifle uses a split ring as well, though I am sure steel ones with a stepped split section (higher performing) are advertised as non original replacements.
    How does a stepped split section work? I can't quite visualise it.

    Quote Originally Posted by dvd View Post
    I think there is absolutely nothing that a half decent split ring cannot handle in airgun cylinder pressures since they have been used for ages in high compression turbo-charged diesel engines and last many years in the harshest compression cycle one can imagine.

    I think a reasonably competent person with a lathe can turn a few rings effortlessly if the cylinder bore is still true and the piston groove/cylinder dimensions are known. I would hate to loose more of what little power these fine pistols make by fitting leather washers.
    Wandering off topic now but I wonder how feasible it would be to convert, say, a HW95 to a PB ring seal?
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    Quote Originally Posted by eyebull View Post
    How does a stepped split section work? I can't quite visualise it.



    Wandering off topic now but I wonder how feasible it would be to convert, say, a HW95 to a PB ring seal?


    Instead of having a straight cut in the side of the ring, the cut would be something like this, making it more difficult for the air to leak past the two ends of the ring

    Last edited by dvd; 19-03-2019 at 05:38 PM. Reason: Cant get the image to appear in the post

  5. #20
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    having a problem posting an image of the ring

    Hi eyebull,
    If you google WaffenGotha and look for the parts list of the FWB300, they have a tuning version of the standard ring for the FWB300S.
    You should be able to see it quite clearly as they have pictures of both the standard and the tuning versions of the ring. The stepped ring is the tuning version.
    I hope that helps as I can not copy the images and get them to stick in my post.

  6. #21
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    Quote Originally Posted by dvd View Post
    Agree with that 100%.
    The FWB 300 rifle uses a split ring as well, though I am sure steel ones with a stepped split section (higher performing) are advertised as non original replacements.

    I think there is absolutely nothing that a half decent split ring cannot handle in airgun cylinder pressures since they have been used for ages in high compression turbo-charged diesel engines and last many years in the harshest compression cycle one can imagine.

    I think a reasonably competent person with a lathe can turn a few rings effortlessly if the cylinder bore is still true and the piston groove/cylinder dimensions are known. I would hate to loose more of what little power these fine pistols make by fitting leather washers.
    Not sure how relevant the very different set up in a diesel engine is?

    But refer back to the opening post and the link there - my MKI with leather washer is reasonably powerful and certainly trumps my Senior with piston ring that doesn't seal...
    Max; looking for: Baikal IZH 61 side lever rifle

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    Quote Originally Posted by felix gunner View Post
    Not sure how relevant the very different set up in a diesel engine is?

    But refer back to the opening post and the link there - my MKI with leather washer is reasonably powerful and certainly trumps my Senior with piston ring that doesn't seal...
    The relevance is that both Webly and diesels use rings to achieve the same task, ie building up pressure rapidly. One caveat for metal rings in both instances is that the bore must be perfectly round and not scored to achieve a perfect seal.
    Leather/synthetic seals are more forgiving in this respect as they adapt and swell to fill any imperfections in the cylinder.

  8. #23
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    Before machining a piston down to take a leather seal, I would be tempted to drill and tap the end and fit a ptfe one from a Premier to see if that improves things. You would lose a little off the stroke but if the Bronze ring is that bad then the slightly shorter stroke shold not make much difference if the Premier seal works.
    If the Premeir seal works, you can then either leave it in place or go for the leather washer. If there was no improvement you could still go for the leather seal (I do like leather seals) but I'd be thinking that maybe it was the cylinder that was out of plonk.
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  9. #24
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    Quote Originally Posted by dvd View Post
    The relevance is that both Webly and diesels use rings to achieve the same task, ie building up pressure rapidly. One caveat for metal rings in both instances is that the bore must be perfectly round and not scored to achieve a perfect seal.
    Leather/synthetic seals are more forgiving in this respect as they adapt and swell to fill any imperfections in the cylinder.

    Hmmm, I think this is being dragged off topic but maybe the use of a ring (single in the Senior) that happens to be split is as much of a similarity as it gets. The ft is much tighter in an engine, oil is a critical part and there are usually three of them.
    Max; looking for: Baikal IZH 61 side lever rifle

  10. #25
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    Quote Originally Posted by ggggr View Post
    Before machining a piston down to take a leather seal, I would be tempted to drill and tap the end and fit a ptfe one from a Premier to see if that improves things. You would lose a little off the stroke but if the Bronze ring is that bad then the slightly shorter stroke shold not make much difference if the Premier seal works.
    If the Premeir seal works, you can then either leave it in place or go for the leather washer. If there was no improvement you could still go for the leather seal (I do like leather seals) but I'd be thinking that maybe it was the cylinder that was out of plonk.
    I don't know Guy, TBH I'm looking for reliable fit and forget and my experience with good old leather is it works.

    There is also a part of me that is horrified about introducing a 'plastic' part into my lovely old Senior.
    Max; looking for: Baikal IZH 61 side lever rifle

  11. #26
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    Senior Pistol Ring

    Years ago in the AGW there was an article on using an O ring as replacement in the Senior, I tried it once with little success, I still have the nos Senior piston ring I bought in an Edinburgh gunshop in the early 80's, but never fitted lying around somewhere!

  12. #27
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    some one converted a senior to a c02 pistol.
    https://forum.vintageairgunsgallery....l-john-walker/

  13. #28
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    engines usually use 2 or more rings so that the gap is overlaped so i guess to be perfect you could make a couple of thinner rings on a lathe - it would be intresting to see if it makes much difference but it should seal very well

  14. #29
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    I recently replaced the spring and breech seal in my Senior and it has increased the power but not dramatically. After reading the OP I measured the hole in the new rubber breech seal to be 3.5mm
    With a 4.5mm barrel I would have thought this is a restriction but don't know enough about fluid dynamics - tempting to drill it out to 4.5mm but I'll do a bit of googling on transfer ports and breech seals!
    I know what you mean about introducing plastic into a Senior - it doesn't seem right even using a rubber breech seal. I would be tempted to leave well alone and just get something else if you need more power. Any gains you get will be so minimal anyway. It is frustrating that the piston ring doesn't seal a bit better though - but I wonder if the stepped design seals much better under power - ie at slow speeds it isn't compressed against itself or the groove it rides in.

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