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Thread: Hw35 Leather or synthetic piston seal ?

  1. #1
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    Hw35 Leather or synthetic piston seal ?

    Hi chaps
    I have a Hw35 that I am doing a service on, I am fitting a TBT kit with a new mainspring,the leather piston seal is in good condition.But would I get any improvement in fitting a synthetic seal and adapter over the leather one?.The synthetic piston seal and adapter is £28 + postage from Chambers.
    Any info would be appreciated .
    Regards
    Les.

  2. #2
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    Don't do it, Les.

    The steel adaptor not only adds weight to the piston it also shortens the 65mm stroke, a better bet is to buy a complete synthetic sealed piston --- Knibbs had them on offer a while back

    http://www.airgunspares.com/store/pr...Part-No.-9192/

    The synthetic sealed piston has a 4mm longer stroke than the leather sealed piston.

    If you get stuck I'd be happy to collect one and post it to you.



    All the best Mick

  3. #3
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    Mick, I have acquired a spare 35 (leather seal fitment) piston and at first glance can't see any reason I can't just machine the end to take the synth seal, and maybe gain a mill or two of stroke... whatdaya reckon ?
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  4. #4
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    Quote Originally Posted by T 20 View Post
    Don't do it, Les.

    The steel adaptor not only adds weight to the piston it also shortens the 65mm stroke, a better bet is to buy a complete synthetic sealed piston --- Knibbs had them on offer a while back

    http://www.airgunspares.com/store/pr...Part-No.-9192/

    The synthetic sealed piston has a 4mm longer stroke than the leather sealed piston.

    If you get stuck I'd be happy to collect one and post it to you.



    All the best Mick
    Hi Mick
    Thanks for the great advice mate.Thats very good of you to offer your valuable time and effort Sir.;-).
    The gun was doing about 9 ftlbs with the old spring and was shooting nicely .Do you think it will be a upgrade in shooting manners and ftlbs energy ?, it's a .177 btw.
    Les..
    Last edited by les allam; 05-12-2017 at 09:32 PM.

  5. #5
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    Quote Originally Posted by Jon Budd View Post
    Mick, I have acquired a spare 35 (leather seal fitment) piston and at first glance can't see any reason I can't just machine the end to take the synth seal, and maybe gain a mill or two of stroke... whatdaya reckon ?
    Hi Jon.

    I normally machine the front face of the leather sealed piston back to expose more rod, then thread the rod and screw on an alloy adaptor for the synthetic seal, so ending up with 71mm stroke --- this also involves extending the cocking slot in the piston rear wards a tad to gain clearance.

    A 71mm stroke is about as much as you can go without altering the woodwork and running into other cocking problems.

    If you machine the front of the leather sealed piston as you describe you'll run into cocking problems due to the stroke and you'll find you have to extend the piston slot that far back you'll break through the skirt.




    All the best Mick

  6. #6
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    Quote Originally Posted by les allam View Post
    Hi Mick
    Thanks for the great advice mate.Thats very good of you to offer your valuable time and effort Sir.;-).
    The gun was doing about 9 ftlbs with the old spring and was shooting nicely .Do you think it will be a upgrade in shooting manners and ftlbs energy ?, it's a .177 btw.
    Les..
    The last 35 I bought from Micky2 on here was a .177" synthetic sealed gun and ran very nicely at just below 12ftlbs, Les.

    So as long as your cylinder is sound changing to a synthetic sealed piston should keep it running nicely --- and having a little bit more swept volume gives a little more wriggle room for tuning.



    All the best Mick

  7. #7
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    Quote Originally Posted by T 20 View Post
    The last 35 I bought from Micky2 on here was a .177" synthetic sealed gun and ran very nicely at just below 12ftlbs, Les.

    So as long as your cylinder is sound changing to a synthetic sealed piston should keep it running nicely --- and having a little bit more swept volume gives a little more wriggle room for tuning.



    All the best Mick
    Ok Mick, that sounds like a worth while upgrade.
    If I can take you up on your kind offer regarding the knibbs piston that would be great.
    YHPM
    Kind regards
    Les..

  8. #8
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    Quote Originally Posted by T 20 View Post
    Hi Jon.

    I normally machine the front face of the leather sealed piston back to expose more rod, then thread the rod and screw on an alloy adaptor for the synthetic seal, so ending up with 71mm stroke --- this also involves extending the cocking slot in the piston rear wards a tad to gain clearance.

    A 71mm stroke is about as much as you can go without altering the woodwork and running into other cocking problems.

    If you machine the front of the leather sealed piston as you describe you'll run into cocking problems due to the stroke and you'll find you have to extend the piston slot that far back you'll break through the skirt.


    All the best Mick
    Sounds perfect, thanks mate; I think I'll be doing exactly this over the xmas hols when the hubbub in the house gets too much for me

    (sorry for the slight threadjack Les )
    Last edited by Shed tuner; 06-12-2017 at 06:25 PM.
    Always looking for any cheap, interesting, knackered "project" guns. Thanks, JB.

  9. #9
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    Thumbs up

    How about machining a new piston head to take an O ring?

    I have this tuned one and it's smoother than a wench's inner thigh, It shoiots superbly too

    Pic 1

    Pic 2

    I made one of these for an airsporter mk1 as the leather seal was kaput although it wasn't as good as the one in the HW35

    Pic 1

    Pic 2




    John
    for my gunz guitarz and bonzai, see here
    www.flickr.com/photos/8163995@N07/

  10. #10
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    Quote Originally Posted by johnbaz View Post
    How about machining a new piston head to take an O ring?

    I have this tuned one and it's smoother than a wench's inner thigh, It shoiots superbly too

    Pic 1

    Pic 2

    I have already done that, John

    http://www.airgunbbs.com/showthread....10#post2931510

    The finished gun and piston was shown in Jim's Real Airgun Sport.

    Unfortunately my doctor won't allow me to use any machinery that I could fall into and kill myself at present, so I couldn't offer to make Les an O ring piston head.



    All the best Mick

  11. #11
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    IMO - keep original.
    Founder & ex secretary of Rivington Riflemen.
    www.rivington-riflemen.uk

  12. #12
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    Thumbs up

    Quote Originally Posted by T 20 View Post
    I have already done that, John

    http://www.airgunbbs.com/showthread....10#post2931510

    The finished gun and piston was shown in Jim's Real Airgun Sport.

    Unfortunately my doctor won't allow me to use any machinery that I could fall into and kill myself at present, so I couldn't offer to make Les an O ring piston head.



    All the best Mick
    Crumbs Mick, Take it easy mate, There's always later to play on your lathes/Millers!

    My old Faircut lathe is worn out, I have a nice 1950's Myford that's nice and tight on the ways but no room to get it set up until I clear the garage somewhat!



    John..
    for my gunz guitarz and bonzai, see here
    www.flickr.com/photos/8163995@N07/

  13. #13
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    Quote Originally Posted by les allam View Post
    Hi chaps
    I have a Hw35 that I am doing a service on, I am fitting a TBT kit with a new mainspring,the leather piston seal is in good condition.But would I get any improvement in fitting a synthetic seal and adapter over the leather one?.The synthetic piston seal and adapter is £28 + postage from Chambers.
    Any info would be appreciated .
    Regards
    Les.
    If you do decide to go down the adaptor route let me know, I have three sitting in my spares box, your more than welcome to one for the cost of postage buddy
    Nick

  14. #14
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    Quote Originally Posted by Simmo View Post
    If you do decide to go down the adaptor route let me know, I have three sitting in my spares box, your more than welcome to one for the cost of postage buddy
    Nick
    Thanks for the kind offer Simmo.
    Mick's already sorted the synthetic seal piston for me.
    Atb
    Les..

  15. #15
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    I've just found an old post which shows why I don't recommend fitting the adaptor and synthetic seal to a leather sealed piston:-

    Quote Originally Posted by T 20 View Post
    Here's the three strokes and weights of the three setups :-

    Factory Synthetic sealed piston ------------- 69mm stroke - piston weight 264g

    Factory Leather sealed piston --------------- 65mm stroke - piston weight 294g

    Leather sealed piston adapted to synthetic - 61mm stroke - piston weight 321g

    All the best Mick

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