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Thread: More Airsporter help please

  1. #16
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    Quote Originally Posted by philcbr View Post
    Hi all

    as requested more pictures added.
    While polishing the piston I did not do the end of the rod that inserts in to the trigger block, it does not have any noticable wear marrks on the end.

    http://i513.photobucket.com/albums/t...pswuqbdecn.jpg

    http://i513.photobucket.com/albums/t...psu09r4vzm.jpg

    I will assemble the gun tomorrow minus the spring and try suggestions from the group.

    Regards

    Phil.
    In one of your photos, you are showing the trigger cocked and the sear engagement part of the piston rod well behind the main sear, so that part of the geometry is correct. Therefore, when the spring is in it is either becoming coil bound, or the end of the piston rod is not long enough to bear on the back end of the main sear in order to cock the trigger, or the cocking lever/slot is mis-matched, such that the piston is not being pushed back far enough.
    Happy Shooting!! Paul.
    "We cannot solve our problems with the same thinking that we used when we created them" - Albert Einstein.

  2. #17
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    Distance

    I have a flat top piston (mk4) which measures from to skirt to the bent face one and three quarter inch .

    I have a cone top piston (mk2) which measures from the skirt to the bent face one and twenty three
    thirty seconds of an inch .

    So of the two pistons I have on the desk I am sitting at the distance of the cone top is one thirty second
    shorter than the flat top piston .

    The measurements were taken using a vernier caliper so reasonable accuracy .

    Both these pistons are standard with no polishing .

    Cheers Crowbar

  3. #18
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    Thought

    I seem to remember somebody having a similar problem that the piston would not latch .
    When the action was split the trigger block unscrew from the steel comp tube end plug leaving said
    plug still screwed into the comp tube and having to be removed individually .

    The trigger block is joined to the end block by a hollow bolt which the piston rod passes through,
    this hollow bolt has a large round head and friction splines on the face of the head.

    These friction splines mate with the friction splines on the comp back block to lock them together .

    When the trigger block screws off the back block it is because the comp block has seized in
    the comp tube and the force needed to free it causes the locking splines to ride over each other altering
    the setting and the trigger won't latch.

    Cheers Crowbar

  4. #19
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    Quote Originally Posted by philcbr View Post
    Hi all

    as requested more pictures added.
    While polishing the piston I did not do the end of the rod that inserts in to the trigger block, it does not have any noticable wear marrks on the end.

    http://i513.photobucket.com/albums/t...pswuqbdecn.jpg

    http://i513.photobucket.com/albums/t...psu09r4vzm.jpg

    I will assemble the gun tomorrow minus the spring and try suggestions from the group.

    Regards

    Phil.
    Phil re query on bucket pic, I have one that measures 56mm on the dimension you ask. It is 44mm to the actual latching point.

    Baz
    BE AN INDEPENDENT THINKER, DON'T FOLLOW THE CROWD

  5. #20
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    Although I can't add anything of use to this thread, it is fascinating and I am waiting in anticipation to hear the eventual correct diagnosis and hopefully happy ending

    These threads are like soap operas for airgun nuts

    Good luck, can hardly wait for the next instalment

  6. #21
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    Correction

    The hollow bolt head is hexagon not round as stated .

    Cheers Crowbar

  7. #22
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    Jun 2006
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    luton
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    Hi all

    Thanks for the responses, the plot thickens.
    Crowbar and Baz have kindly supplied measurements of the distance between the piston skirt and the latching rod end, mine appears to be different.
    Baz measured 56mm form skirt to end of the rod mine is 51,3 and 44mm from skirt to latching point, mine is 40.50mm.
    This could explain why some threads have been removed from the part that screws in to the cylinder, allowing the latching rod to travel further in to the trigger block.
    I have noticed the latching rod is a separate part to the piston body, this being brazed to secure it in place. Could this have been modified to make it shorter in an attempt increase power? When I removed the piston from the gun originally I noticed it had a “blob” of braze on the outside of the piston surface. My thought originally was that someone had tried to increase the weight of the piston by doing so, attempting to increase power again?
    I’m adding more pictures for reference. I made a video of the cocking action but photobucket will not load it, it’s not very large only 10mbit but I’ve given up wasting time on it.

    http://i513.photobucket.com/albums/t...psqvuudcxn.jpg

    http://i513.photobucket.com/albums/t...psl7t6nugs.jpg

    http://i513.photobucket.com/albums/t...ps4yuf3sip.jpg
    Regards
    Phil

  8. #23
    ggggr's Avatar
    ggggr is offline part time super hero and seeker of justice
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    Just take the piston out of the cylinder and push the rod back into the trigger block and see if it latches every time/ that the trigger is working ok.
    Then put the piston back in the cylinder but leave out the mainspring/ guide and cocking linkage. Now slide the piston back using a screwdriver/ rod or dowel (it may need a little force to actually latch ----as normally you have leverage) and see if it latches. If it doesn't then that would suggest that the rod or piston skirt are wrong, but in the pics you show of the rod in the trigger already they appear to be ok.
    If the gun latches, then fit the cocking linkage and repeat and take it from there. The slot in the piston does not appear to be worn or the lug on the end of the cocking rod. I an wondering (although I've never heard of it on an Airsporter) the cocking arm is slightly bent?

    It is a pity there is not someone close by with a piston or another trigger block to try.
    Cooler than Mace Windu with a FRO, walking into Members Only and saying "Bitches, be cool"

  9. #24
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    More pictures added showing piston position when the trigger latches.
    Do you guys think the issue is with the length of the piston rod as the piston should not have to go that far in to the cylinder threaded section surely ? The piston could not travel that far if a section had not been removed from the threaded part of the trigger block.

    http://i513.photobucket.com/albums/t...ps3wqfyczw.jpg
    http://i513.photobucket.com/albums/t...psbly1axsg.jpg
    http://i513.photobucket.com/albums/t...psjf3xqwjp.jpg
    http://i513.photobucket.com/albums/t...pspicfzaue.jpg

    Phil

  10. #25
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    This is a simple mechanism, in which anyone with a bit of methodical measurement/comparison could diagnose the cause of the reported problem, with ease.

    With all due respect, several people (e.g. Guy ggggr) have made solid suggestions and/or observations, which you seem to just ignore, preferring instead to post more pictures and questions.

    Perhaps you should take the gun to an airgunsmith, or see if a knowledgeable/experienced member lives near enough and would be willing to help you out.
    Happy Shooting!! Paul.
    "We cannot solve our problems with the same thinking that we used when we created them" - Albert Einstein.

  11. #26
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    luton
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    Which suggestion have I ignored? I have assembled the gun minus the spring and reported my findings, mostly using pictures.
    As I have said pushing the piston in to trigger block by hand works fine.
    The threaded section attached to the trigger block has been shortened by a previous owner for what purpose I do not know, I can only speculate on that.
    Baz has supplied measurements from his piston that are different to mine so I have concerns in that area.
    As I do not know the history of the gun I’m trying to gather as much information as I can to find a possible solution to the problem.
    In one of your replies you suggested the trigger was assembled incorrectly, however when I posted more pictures from a different angle you said it looked ok. In another reply you suggested the piston rod might be short, I agree with you that might be a possibility.
    I also agree with you this is a simple mechanism, but if the parts have been altered they might not function properly when assembled.
    As I do not have another gun to compare parts with I seek the experience and knowledge from members of this forum, even you.
    I note you are a well-established member of this forum so I guess you have more knowledge than me on the subject of spring powered airguns. I’m sure whatever knowledge you have on the subject came from asking questions and having a go at repairing things yourself.
    If you are fed up with me asking questions and posting pictures just ignore my post, simple.

    Phil
    Last edited by philcbr; 02-04-2017 at 05:42 AM.

  12. #27
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    Following further enquires it does seem the piston rod is approximately 6mm short, I have no idea how this has occurred.
    I am considering trying to disassemble the piston to establish if it has been modified?
    Does anyone have information regarding the manufacture of the rolled piston assembly? I know it is brazed together but in what order. There looks to be three parts, the piston rod. Rolled tube and the piston end that the leather seal fits on.
    Has anyone taken one apart? Any information regarding this procedure would be appreciated.
    If this is not a practical proposition then I will have to consider trying to purchase a replacement piston.
    Many thanks.
    Phil
    Last edited by philcbr; 13-04-2017 at 11:33 AM.

  13. #28
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    If I remember correctly, the cocking rod - i.e. the bit you have determined is short - is removeable. Problem is, I don't recall how it comes out, but I think it should unscrew. If you look on Chambers site they are advertising the piston as 'complete' with rod', which reinforces this. (£66.00, by the way)

    If you look down inside the piston from the rear, you may see a slotted nut, in which case you need to make a wrench from a suitable tube, with two raised lugs to engage the slots in the nut and unscrew it.

    In theory you could make or have a new rod made. The difficult part will be case hardening in way of the trigger sear.
    Happy Shooting!! Paul.
    "We cannot solve our problems with the same thinking that we used when we created them" - Albert Einstein.

  14. #29
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    Quote Originally Posted by Airsporter1st View Post
    If I remember correctly, the cocking rod - i.e. the bit you have determined is short - is removeable. Problem is, I don't recall how it comes out, but I think it should unscrew. If you look on Chambers site they are advertising the piston as 'complete' with rod', which reinforces this. (£66.00, by the way)

    If you look down inside the piston from the rear, you may see a slotted nut, in which case you need to make a wrench from a suitable tube, with two raised lugs to engage the slots in the nut and unscrew it.

    In theory you could make or have a new rod made. The difficult part will be case hardening in way of the trigger sear.

    The MK2 doesn't unscrew, Paul.

    The whole lot is brazed together, the rod is brazed into the end cap, then the body is brazed on.





    All the best Mick

  15. #30
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    Thanks for the replies.
    I suppose I might just as well get the blow lamp out and get on with trying to take the thing apart, I have nothing to lose as it is of no use in its current state.
    Shame the new seal is not removable without damage.

    Phil

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