Canadian Airgun Forum

The #1 Community for Airguns in Canada!
It is currently Wed Nov 13, 2019 7:35 am

All times are UTC - 5 hours


The Canadian Airgun Forums are a place for people to discuss and learn about airguns and the airgunning sport in Canada. There are lots of discussions about airguns, airgun accessories, reviews, modification and repair information, airgun events, field target and free classifieds!

 

You need to register before you can post: click the register link to proceed. Before you register, please read the forum rules. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload your own pictures, and access many other special features. Registration is fast, simple, and absolutely free! To start viewing messages, select the forum that you want to visit from the selection below.








Post new topic Reply to topic  [ 53 posts ]  Go to page 1, 2, 3, 4  Next
Author Message
PostPosted: Sat Jun 03, 2017 7:09 pm 
Offline

Joined: Fri May 05, 2017 11:41 pm
Posts: 48
Location: Western NV
For Guys in the know about psi etc,

Bob, are you around??

This question deals with the strength of STEEL co2 cylinders of the 88 & 90 gram weights/sizes,
the spec's on these cylinders is as follows, there are 2 lengths,

The below info is right on the OEM label,
that is attached to the cyl's.

1. Short cyl = outsider dia = 1.580",
total length = 6", 7/8'' for the total threaded neck length,
net weight =88.0 grms,
fill density = 75.86%,
cyl test pressure = 4000psi
cyl burst pressure =8100 psi
cyl test temperature = 70* to 160*F

2. Long cyl = outside dia = 1.380"
total length = 8", 1-1/4" for the total threaded neck length,
net weight =90.0 grms,
fill density = 75.86%,
cyl test pressure = 4000psi
cyl burst pressure = 8100 psi
cyl test temperature = 70* to 160*F

Now the 64,000$ question,
Could these cylinders be adapted for 1100 - 1400 #'s of MAX HPA,
using a hand pump and tapped/drill fill adapter,
for a QB 79 AR.

If these cylinders could be SAFELY adapted,
they would make a neat compact air source for this QB-79 AR,
for short shooting sessions etc.

Thanks,
Don

_________________
"Speeds fine, but accuracy is final"

QB-79, 22 cal
Airforce Condor 22 cal - pending


Top
 Profile  
 
PostPosted: Sat Jun 03, 2017 11:12 pm 
Offline
User avatar

Joined: Thu Feb 02, 2006 11:35 pm
Posts: 3099
Location: Alberta Canada
It has been done by some.

In layman's terms of mathematics upon pressure vessels. Going off the manufactors label.

If a pressure test is 4000psi that's 150% over said Maxium Safe Operating Pressure.
So 4000psi ÷ 150% × 100 = 2666.6psi. Being that Co2 is Cryogenic fluid like Nitrogen and 88 & 90 gm cartridges are deemed by industry as a rough service pressure vessel, just like 8 and 12gm Co2 carts. And designed for Single Use Only.
2666÷50% × 100 = 1333.3 psi so essentially it would be good to 1334psi maximum operating pressure. Now if you follow a Co2 expansion graph believe it puts you within the 30ish C area of temperature to expansion to pressure. Going off memory here.
But now your talking taping and threading the body. Foster fill nipples are National Pipe Thread which requires a minimum of 3 full threads of engagement to be operational not necessarily safe 3 threads @ 1000psi 4 threads @ 2000psi and 5 @ 3000psi etc etc. Which means you require a metal thickness of approximately 0.112" for 1000psi. And thicker for more thread engagement to more pressure. IIRC 88gm & 90gm carts are 0.068 ish. So is it safe... not likely.
The Weekest point to your thoughts is how the fill valve and will be secured in a safe operational manner. Just like pinning valves.
Now the use of a repeated fill upon a vessel designed to be Single Use by the manufacturer.

Question for those reading this, Now Is This A Safe way of a modification?

Regards

_________________
May the cry of the pack be with you upon your hunt

Whitewolf


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 4:26 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Thanks for the information. I'd only comment that the bottom of the 90g tank is a lot thicker than. 068, it's more like 1/4", which is where guys put the fill nipples.

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 5:25 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Bob was using the 16g co2 cartridge at 1500psi regularly, and seemed to think that was safe. I believe he mentioned it had a 250bar max safe working pressure and greater than 300bar burst, which makes it probably close to the same as these 88 and 90g. I'm not sure but I think he only stopped at 1500 because the 392 pump arm wouldn't take more pressure.

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 5:27 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Sorry, I guess if you go by the burst pressure, these bigger cylinders seem to have a much higher burst than the 16g.

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 5:30 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Here's how I mounted mine. I even ended up putting a second one of the other side to balance it out and give more shots, though it makes for extra weight. Image

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 5:35 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Sorry, forgot to resize, here it is smaller [emoji4] Image

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 5:38 am 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
I mounted a bracket on the back sight and glued the cylinders to it to keep them safely mounted. With the scope though, it's over 9lbs now though so pretty heavy.
Anyway you are asking about safety, so I won't comment further.

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 10:31 am 
Offline
User avatar

Joined: Fri Jan 22, 2010 1:17 pm
Posts: 1812
Location: Kingston, ON
I modded a few 88g cylinders to take bulk CO2 and it has worked OK for me.
The cylinder itself is OK for CO2, so 1500 psi isn't an issue
The ASA adapter same thing.
The questionable area is the threads in the cylinder for the fill nipple.
Cut the threads clean and neat in the cylinder. You probably need an adapter to contain the plunger for the check valve on the foster.
The adapter I used is brass. I have tested it at 1500 psi with HPA and it didn't explode, but that doesn't mean it's safe - only that mine didn't fail at 1500 psi.
I never fill it over 1000 psi with HPA. I have used it with CO2 mostly.


Attachments:
qb1.jpg
qb1.jpg [ 47.99 KiB | Viewed 563 times ]
QB3.jpg
QB3.jpg [ 452.16 KiB | Viewed 564 times ]
qb2t.jpg
qb2t.jpg [ 541.81 KiB | Viewed 564 times ]

_________________

Duke ))))----//----------==
Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 10:56 am 
Offline
User avatar

Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8973
Location: Coalmont BC
In general, reusable CO2 cylinders are rated at 1800 psi, which puts their hydrostatic test pressure at (5/3 x 1800) = 3000 psi, and that is the value of the burst disc fitted, to protect from filling past the test pressure.... Single use CO2 cylinders have no burst disc, so right there is a concern, extra care must be used to prevent overfilling.... By ASME rules, pressure vessels must have a 3.5:1 safety margin to burst above their working pressure, so 1800 psi x 3.5 = 6300 psi min....

Your tank seems to be well over the test and burst pressures for a reusable CO2 cylinder, as was the burst pressure on the 16 gr. CO2 I used, which was 500 bar, which is 7250 psi....

Image

It would seem to me that all CO2 cylinders are properly engineered for at least an 1800 psi working pressure.... Kim makes an interesting point about single use cylinders being derated if refilled, but I have no info on that.... Steel cylinders working below 50% of their yield point should have no concerns about fatigue, however.... so up to (4000/2) = 2000 psi for yours.... or (3600/2) = 1800 psi for my 16 gr....

Kim's points about the wall thickness where you are tapping for the Foster are correct.... If you indeed have 1/4" of thickness on the bottom, where you are installing it, I would be OK with that personally, up to the 1800 psi working pressure for CO2.... Personally, I would treat the tank as if it had a 1.8K burst disc installed (putting one in would be best).... Since those typically fail at about 1500 psi, that should provide adequate safety, providing your fill fitting, valve, etc. etc. are all installed safely, and intended to meet or exceed the test pressure of 4000 psi....

Bear in mind, I'm NOT an Engineer, and that Kim is better qualified to give advice on things like this.... Personally I would have no problem using it for CO2, or with HPA up to the burst point of a 1.8K disc (1400-1500 psi).... but that's just me.... and subject to all work being properly done....

Bob

_________________
Dominion Marksman Silver Shield - 5890 x 6000 in 1976, and downhill ever since!
Airsonal;
Too many! Springers, Pumpers, CO2, but I love my PCPs and developing them!
Proud Member of the 2000+fps Club!


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 1:27 pm 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Looks great! Here is a foster fitting with a built in stop rated at 4500psi. It's available in 1/8 npt or metric.. (AliExpress) choose epacket for shipping though if you buy this if you don't want to wait two months! I've been filling my qb78 to 1500 as well with no trouble though that means nothing as said earlier, but with a 8000psi burst I'm thinking it's safe. Image

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 1:29 pm 
Offline

Joined: Fri May 05, 2017 11:41 pm
Posts: 48
Location: Western NV
Thanks Guys,

I will have to spend some time understanding the math formulas that are posted,
not my strong suit etc. :rolleyes:

And being that this is my first real AR,
I have lots of steps to take understanding them and how they operate etc.

Thanks for the photo's.

Please note, I do not want to tap/drill the sides of these cylinders,
as IMHO that would be courting a Kaboom, which I prefer to do without.

I was thinking about only the ends, which would seem to have the most thickness and safest etc??

Here is where I noticed the info from,
http://www.ebay.com/itm/Refillable-88g- ... SwnNBXXE8h

As soon as the QB-79 22 cal and Hill hand pump arrive, after it has cleaned, de burred, tested and modded,
to obtain the best all around performance etc.

I want to set it up for both summer use and winter use, and hopefully have the same ballistic's for the 22 cal,
using either power source, in this AR.

That way, I can changed to fit the seasons, as needed etc.
I want accuracy first and power second, for the bird pesting and small game hunting,
I am hoping that I can have both, for each power source, out to 50 yds.

Back to reading all the posts in the mods section. :roll:

Tia,
Don

_________________
"Speeds fine, but accuracy is final"

QB-79, 22 cal
Airforce Condor 22 cal - pending


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 1:35 pm 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
Sorry, again I forgot to resize the picture

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 1:42 pm 
Offline
User avatar

Joined: Sat Nov 05, 2016 10:52 am
Posts: 2926
Location: Caronport, Saskatchewan
You'll find that you get around a 100 fps more speed with the air vs co2, even at around that 1000 to 800 psi level so you might want to rig up an rva on the back or have to different hammer springs you can switch out to keep the same power level each season. I found the greatest and easiest performance boost on the QB78 was simply switching out the stock qb78 transfer port seal for a crosman 13xx port seal. Without any other mods it jumped speed over 100fps on co2!

Sent from my LG-H812 using Tapatalk

_________________
Website: https://airgunarcheryfun.ca/


Top
 Profile  
 
PostPosted: Sun Jun 04, 2017 1:49 pm 
Offline
User avatar

Joined: Wed Jul 01, 2009 3:23 pm
Posts: 3067
Location: Northern Ontario
B&A used to sell a fitting to allow the 88's to be refilled. You may want to check with Baker Airguns to see if they still sell them.
If you are buying pressure fittings from China, keep in mind they have sold fakes before, and may well lie about pressure ratings.

_________________
"The tree of liberty must be refreshed from time to time with the blood of patriots and tyrants." - Thomas Jefferson.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 53 posts ]  Go to page 1, 2, 3, 4  Next

All times are UTC - 5 hours


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
News News Site map Site map SitemapIndex SitemapIndex RSS Feed RSS Feed Channel list Channel list

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

phpBB SEO