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SMK QB78DL Bulk fill conversion problem

Discussion in 'Anything Airgun Related' started by jantar, Mar 29, 2014.

  1. jantar

    jantar Donator

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    I have just bought the bulk fill (air) adapter from TT Robb who specialises in this type of conversion parts and it came quite quickly. Being excited I did what the instructions told me to and then tried to charge it from my bulk fill air bottle. ARGHHHHHH the air leaked out of the reservoir bleed hole as fast it entered!
    Some research now informed me that different manufacturers of the QB78/9 reservoirs locate the safety bleed hole (on the top of the end cap threads but hidden by the barrel) at different distances from the front of the threads! Marvellous, yet absolutely stupid because it makes many of the rifles being unable to be modified to bulk fill air!
    If your rifle, as mine is, has the bleed hole 10mm from the end of the threads then the conversion will not be suitable with the conversion adapter TT Robb supplies. It is not his fault though, the blame lies firmly with the manufacturers of the OEM CO2 reservoirs being unable to work together to one single set of dimensions thereby ensuring that the bleed hole is in the same location on ALL reservoirs.
    My solution, and the only one, is now to buy the extended reservoir made by TT Robb and replace the OEM one with that. Presumably then because he has manufactured both items the conversion will work as he intended.
    I have 2 of these rifles to convert so I am hopeful that once he returns from his holiday on the 4th April (2014) he will reply to the concerns I have messaged him about.
    Need parts for conversions? You really would do a lot worse than to use his 'bits' because they are all well made and decently priced. Delivery is rapid too.
    This is where he can be found;
    http://www.trrobb.com/
    Once my present project is completed I am certain that it will have been worth the hassle...........
     
    Last edited: Mar 29, 2014
  2. Egg

    Egg Major Poster

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    You should check out the Chinese Airgun Forum for all things 78 & 79. I'm afraid T Robb has a bit of a reputation over there for plagiarising parts that other people have made and selling them at top dollar.

    porkyyorky (amongst others) makes quality parts for the QB/XS series and his reputation is top notch.
     
  3. foggybell59

    foggybell59 Engaging Member

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    Hi Jantar,if you cherish your eyes DONT try to run this on HPA as the tubes are only safe @900psi which will give you 10-12 shots,the valve is held by a chinese cheese screw so this must be changed if you dont want it comeing out the back at great force.Then replace every screw & bolt with s/steel ones.But hey this is only my opinion and Ive only built 20 or so,
    cheers Algy;)
     
  4. mick 1986

    mick 1986 Keyboard Hero

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    Trobb is way overpriced for gear that most people can turn on basic lathes!

    instead of shelling more money on his Censored gear, try and remove some material from the end of the tube. That should move the new end cap further down the threads and past the bleed hole.

    if your dead set on using HPA (High Pressure Air), look at getting a 79gas block and a regulated paintball bottle. They are usually regulated to 800/850Psi (roughly the same pressure as Co2 at 20deg C) and thus a safe way to run HPA.
     
  5. jantar

    jantar Donator

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    I have read the replies to date and earlier this morning I had an idea of how to use a work around to make the adapter from TT Robb work. I did this by the simple expedient of installing a second O ring in front of the shoulder before the groove his O ring seats into on his adapter (£29.00) and it was no surprise to me that the the air was then retained in the reservoir.
    I tested it at low pressure initially to ensure that the additional O ring did effect a seal and the after emtying it by dry firing I then re-exemined all of the parts used and re-installed them again before re-charging to 900lbs with air. I test fired it through my chrono and it gave a legal reading of just over 10ft/lbs which is fine for me. I shot until the reservoir was empty again which was a total of 38 shots before the pellets began to drop out of my 20mm test circles. I intend to fit a longer reservoir at some point to give me more shots per fill, along with my changing of all of other components to a higher specification than the originals (screws etc).
    As for TT Robb service all I can say is from my own experience and that he sent the adapter quickly along with the advice that I should stick to 900lbs fill pressure. Because he is at present on holiday and to be wholly fair I shall wait for his return and his reply before I make any other comment on his enterprise. I will no doubt buy another adapter which may be from him or another scource if I can find one (I will try the one suggested in the replies). I have sent a message to a Danish company (Norconia Gmbh)who also market a CO2 adapter which I would expect to also work with air. Once I have a reply I will post it. As for being overpriced, all I can say is that his prices are not too dear. To make the parts yourself it is fine if you own a lathe and have the necessary skills to operate one, many, no most shooters don't. I do not want to remove any material from the end of the tube because I still want it to be able to revert to CO2. My idea is easy, inexpensive and provenly does the job for pence if the O ring has be bought. I used one from my bits and bobs store I had bought to repair a kitchen tap!
    To allay any fears I am very safety conscious partly because I was an armourer whilst in the forces and also because I am responsible by nature so no worries, all of my work will take those into account.
    This afternoon I will do another full test and see how it goes...........
     
  6. mick 1986

    mick 1986 Keyboard Hero

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    The main point about Trobb is that he's ripped someone else's design and making a mint from it, without any acknowledgment to the original designer!

    Dave (aka Porkyyorky) probably hasn't done anything with these rifles that anyone else has done. He's built from parts several rifles and builds custom parts from his own designs (these bulk fill adaptors included), and doesn't charge anywhere near the price you paid (from memory his bulk fill caps are around £7 posted).

    I have no experience of dealing with Trobb, nor do I have any intention of doing so, but if your happy with his services mate, that's all that counts.
     
  7. jantar

    jantar Donator

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    It would be nice if someone could give me the contact of Dave (porkyyorky) so that I can place a bit of business his way. Like anyone else I do not particularly like those who use the ideas of others for their own profit but when there is no information forthcoming about anyone who can supply the parts I need, and that the internet only threw up TT Robb apart from Archer's in the US who cannot export to the UK anyway) then I had no other option than to buy from him.
    Obviously I would prefer to use trusted manufacturers with a proven record.
    Please someone.......give me the contact details of anyone reputable who can supply bulk fill adapters to convert a pair of QB78's to HPA......
    Cheers
     
  8. bobbie1

    bobbie1 Busy Member

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    As said above the best way to use HPA is a regulated bottle set around 850 psi on a
    QB/XS 79 ,
    this will give you 150 or more consistant shots with safety, as most of the time you will be running at a lower psi than co2 without the cost or hassle ,,
     
  9. Egg

    Egg Major Poster

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    Chinese Airgun Forum - member name porkyyorky (real name Dave) and a really nice guy. foggybell59's a well known face on that forum as are a few other guys that are members here (a good few of them pitched-in with SteveO_R10's XS79 HPA conversion on this thread - http://www.airgunforum.co.uk/forums/showthread.php/173121-SMK-XS79-Renovation-amp-stock-wood-type)
     
  10. jantar

    jantar Donator

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    Thanx for the info, I will try to contact using the thread you gave me....
    Kind Regards
     
  11. ped

    ped Keyboard Hero

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    leeds
    THESE TUBES ARE FOR BULKFILL CO2 NOT HPA they're not pressure rated for unregulated hpa -the valves ports are too big to use as a pcp and you'll start getting valve lock around 1200psi
    if you want to go hpa fit a xs79 gas block and a REGULATED paintball tank
    ped
     
  12. jantar

    jantar Donator

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    Hi Ped,
    Thanx for the info and its already in hand thanx to steveO_R10 who has given me a list of the parts he has used in his conversions and which I am now in the process of buying.
    I have only tested the rifle in its original form after fitting the TT Robb adapter to 800lbs (the CO2 caplets fill the reservoir to 950lbs which left a decent safety margin of reduced pressure) to see if it was viable, the parts I had bought did not leak when used and would not go further anyway pressure wise because I am used to working with HPA and being a former engineer know all too well the consequences and dangers. Once you have seen a workmates head almost completely taken off while using HPA (he died at the scene) the lesson tends to stay with you for life. The adapter (£29.00) allowed air to leak from the reservoirs safety hole and so I had to add an additional O ring to the stem of the adapter as a temporary work around in order to test it. Now it has been tested it has been discharged by dryfiring to see the shot count and do a chrono test. It is now back in the cabinet waiting for the parts to arrive and me to have a free day to get it all completed.....
    Fun days ahead? We will see...........
    Regards
    Ray
     
    Last edited: Mar 31, 2014

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