GTA
All Springer/NP/PCP Air Gun Discussion General => Machine Shop Talk & AG Parts Machining => Engineering- Research & Development => Topic started by: stalil on June 06, 2022, 12:31:25 PM
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Good evening gentlemen. I recently saw a modification on a 300bar, 400cc aluminum bottle which looks suspicious if not dangerous. Somebody drilled and threaded the flat bottom of an aluminum bottle, fitted on an airgun, in order to fit a fill nipple.
Do you think it is safe? Would you do such a mod?
Regards
SL
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I guess it depends on the thickness of the bottom of the bottle, and how many threads of engagement you can get.... I do not know if drilling the bottom of the bottle weakens it or not....
Bob
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Drilling a flat bottom I would think it would be okay but that's just a guess.
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Also, a small hole would pose less risk. Sounds interesting, I may have to measure the base of my AEA bottle... :o
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Just recently did just that to a 500cc 3K aluminum bottle. Fitted to an old school THEOBEN RAPID that had to have bottle removed to fill otherwise. ( what a PITA )
Found the bottom thickness once threaded 1/8-27 NPT has as many or more threads than the Foster fill fitting to be used.
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Just recently did just that to a 500cc 3K aluminum bottle. Fitted to an old school THEOBEN RAPID that had to have bottle removed to fill otherwise. ( what a PITA )
Found the bottom thickness once threaded 1/8-27 NPT has as many or more threads than the Foster fill fitting to be used.
That's what I was thinking that the flat bottom would be thicker than a rounded bottom.
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without being a engineer, I have the sense that a flat bottom is not the ideal shape as a part of a pressurized vessel. Probably it is dictated by the manufacturing proccess. Therefore it is thicker or over engineered in order to offset the non ideal shape and keep everything as safe as possible. However I am not convinced that drilling it is a very safe approach. If I have made a mod which so far has not given any trouble is not a proof that it is a safe approach generally. Anyway, thank you gentlemen for your time.
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For what it's worth ... Allen Zasadny ( AZ ) whom is a Very well respected tuner for many many years now has been doing similar Filler to tank bottom modifications as far back as the 90's with Theobens and similar bottle guns.
Never read or seen an issue with those done in this manor ?
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well, thanks Scott, however never seen these posts. If it has been tested often and by a respected modder then it should be safe. I am just too cautious with hpa. If I knew it earlier it would have made things easier for me in a couple of cases.
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(http://buddyl.com/edr/air/rapid/MFR004-2.jpg)
(http://www.airtanksforsale.com/airguns/AZ-Rapid22DaveG/DaveG22Rapid.jpg)
(https://airgunnationforum.s3.us-east-2.amazonaws.com/57E35252-D3C8-493F-B3FE-55EFE6424DF0.1626736679.jpeg)
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Man, that's one butiful rifle
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Man, that's one butiful rifle
All 3 are different rifles ... all 3 with AZ tank bottom fill fittings added. Note last one has cover removed and the old school PARKER hydraulic to foster filler required shown is attached.
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My Theoben bottle that has the Allen Z fill port on it is just fine. The hole that goes through the bottle is threaded, though there is also an aluminum nut inside the bottle that will pinch the fill adapter to the bottle. There are no issues with this method, as it has been done many times for many years.
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My Theoben bottle that has the Allen Z fill port on it is just fine. The hole that goes through the bottle is threaded, though there is also an aluminum nut inside the bottle that will pinch the fill adapter to the bottle. There are no issues with this method, as it has been done many times for many years.
I like this strategy, you could even put a stainless steel washer and nut on the inside to spread the load more. Only problem is it's hard to use tapered threads like NPT with a nut so teflon tape is probably not going to seal it, you'll need to have an o-ring somewhere.