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Thread: Uneducated Air Rifle Tuners & Uneducated Buyers

  1. #1
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    Default Uneducated Air Rifle Tuners & Uneducated Buyers

    Introduction

    I am a DIY Air Rifle builder & modifier, no Engineering education, self educated with no Certificates to prove my knowledge, but the basics is done according to standards specified by various institutes
    and pressure vessels designed and certified by a Professional Engineer in the profession of pressure vessel.
    All my pressure vessels are pressure tested at higher pressures specified by the Certificates especially for the users that thinks 3000psi = 300bar.

    This thread is all about knowledge to educate yourself and other Air Rifle enthusiasts on high pressure air equipment.
    Doesn't matter if you know, think you know or just want to be educated, this will be refreshing or an eye opener for many.

    This information below will unfortunately implicate some people, I do apologize, but this thread is to heighten safety,
    understanding of pressure vessels and the difference between different terminology.

    STORY BEHIND THIS THREAD

    I have received parts from a modified CP1 bought by a fellow club member from someone on this forum.
    This is not a name & shame thread, but rather a wake-up call for the DIY modifiers and a reference for buyers of modified Air Rifles.

    I was horrified to see the quality of workmanship on this CO2 pistol converted to PCP by this person, which should actually be a HPA conversion
    according to original material.
    I'm sure there were a complete lack of any sort of calculating or indicated danger of use.
    Which means absolutely no clue about the dangers involved or just complete ignorance.

    1. There is no reference on the tube that state intended original working pressure of the vessel.

    2. There is no reference of tested pressure of the vessel after conversion.

    3. There is no reference of max fill pressure of the vessel, other than verbal "I've been filling to 200 bar" statement.

    INFORMATION

    To do a conversion like this, parts need to be designed for that specific force introduced to it, material needs to be rated to handle the design constraints.
    For instance, especially aluminum, which has a fatigue rating of structure over time, which means it might be fine and handle the pressure now, but how
    will it handle the pressure after 20 or 40 or 100 fills.

    The tube itself is a mere 1.5mm wall thickness, no idea what special structure steel the manufacturer used and I'm sure designed to handle the low CO2 pressure of around 550psi (38 bar).
    As reference of tubing I use, a 22mm OD tube with 1.5mm wall thickness has a working pressure of 192 bar, which is in the PCP design bracket, with that data known you need to take in
    consideration the 1.5mm thread pitch cut into the tubing wall. Now you can work out the reduced working pressure and that is a staggering low 1392psi (96 bar). Yes, there is o-ring sealing
    of air before it reaches the reduced wall, imagine that o-ring fails.
    HPA conversion means it should have an external pressure vessel with regulated air supply of around 900 psi (62 bar)

    All this information is from data that I have available to me and not data from the manufacturer or directly from an Engineer,
    but that is only part of the issue I have with this conversion.

    The thread in the original tube is cut to 50% thread engagement, I hope.
    The thread on the conversion part was cut clearly unprofessionally with rounded edges and to my estimation that will defiantly end up less than an overall 50% thread engagement.

    I have no idea what grade aluminum was used, but the grade aluminum intended for use with pressure vessel needs at least 5mm wall thickness for structural strength and to decrease level of fatigue.
    That basic design guideline was not followed on this part.

    What I would like to mention at this point is if you want to build a bomb for yourself, please do not sell that product
    If you do intend to sell the unit, please have a brand name displayed on the unit with Professional Engineer Certificate available stating the design & manufacturing constraints.

    If you do not understand the physical energy contained in a 200 bar pressure vessel, please do a youtube search to grasp the concept of what forces you are actually dealing with.

    BASIC SAFETY

    Basic safety each and everyone of us needs to follow is being vigilant of any pressure vessel handled.
    First thing I do when handling an Air Rifle is checking the visual integrity of the pressure vessel.
    As example, this is not to insult other Air Rifles manufacturers, but a few CZ's has passed through my hands and on each and everyone of them I noticed bubbling under the coating,
    stripping it down you will fined rust and needs to be treated if possible otherwise unfortunately needs to be condemned not just for your safety, but every one around you.
    A lot of the time even experienced Airgun smiths fail to do this basic visual check, as an example an air tube passed through me and the first thing I noticed was a mark on the titanium tube.
    Inspecting it closely it clearly protruded into the wall and immediately the red light went on, obviously went unnoticed passed a few.
    Another basic we all fail to do when an Air Rifle falls, we all jump and check the barrel, that is the last thing you need to worry about, you have a bomb in your hands and the integrity of the air tube needs to be checked above all else.
    When your scuba tank falls over, grab and shout at every one and run away, not run towards the tank to pick it up and check if your filling station is broken.
    Another important fact to be vigilant about is when filling your own PCP or anyone around you filling there's is the rate at which it's been done, because very few read the instruction manual,
    that should be done very slow for those who don't know by now.

    Please feel free to add any educational experiences or extra information to educate our forum members.

    PLEASE DO NOT NAME & SHAME ANYONE ON THIS THREAD, IT IS FOR EDUCATIONAL PURPOSES FOR EVERYONE TO REFER TO AS GUIDANCE

    CHEERS BE SAFE
    I will ask admin to monitor this thread and remove any inappropriate posts, thank you.
    Last edited by UllUllA; 15-06-18 at 10:22.
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  2. #2
    The Oom From T.J.O.P.S
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    Interesting....
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  3. #3
    REP: Outdoor Pitstop
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    Very, very, good post.
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  4. #4
    Marksman

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    Thanks, we are working with potential bombs. It is definately something to keep in mind, especially for us DIY enthusiasts with homemade hpa conversions.
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  5. #5
    Inactive Member

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    Excellent post.

    And thanks CK.

    Cheers.
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  6. #6
    Sharp Shooter
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    Great informative post! This can NOT be overstated!
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  7. #7
    REP: Air Rifle Services

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    Well said sir
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  8. #8
    MRP

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    Working with boilers for 14 years of working pressure around 10-50bar ( yes it's different because it's 180-250degrees) , made me wide awake at what's inside a pcp. I don't think people realize what they working with ( scuba blasting etc). Scary

    For example I have a old scuba tank, it suddenly decides when it pushes 300bar into my gun all at once!! Imagine trying to fill a so called cp1 pcp conversion to what is recommended 100 or so bar? Like playing Russian roulette!
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