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PostPosted: Fri Jun 21, 2013 11:11 am 
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Joined: Wed Mar 27, 2013 10:14 am
Posts: 4
Location: Somewhere in Quebec
Hi everyone!

I have made a valve mod that I want to share with the community, this is for learning purpose only, try it at your won risks, I will not be held responsible in any ways if anything goes wrong.

You need a minimum of tools such as a drill press, wheel cuter and some files at the very minimum (a metal hand saw could also do the trick).

This mod allows to remove up to approximately 90% of the aluminum (front) part of the valve, as well as getting the spring and washer out of the way, creating much less restriction and adding extra air volume right before the valve stem.

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I did remove around 75% of the front part, I thought I would remove more of it but decided that I was satisfied with the mod as it is, for now. I have tested it for leaks and there is none, I didn't have time to check the results with a chrony since I am currently building my own and the only person I know who has one is gone for vacations for a few weeks.

I had to do a groove on the stem rod for the circlip, I did that by using a lathe cuter (my lathe needs a new motor sadly) and I used my drill press to turn the part, that did look curious but it worked. I also had to enlarge the hole on the retaining block (black part) so that the valve spring and the orings could go through. It was fun to put it together, I had the parts flly out on first attempt. The circlip could be a weak point, if it would go off after a shot, the gun could go in free flow, that wouldn't be a danger I believe but it would look funny to other people if you are in a shooting range ^^. At first I wanted to thread the stem rod and put a nut on it, it would allow to adjust the valve spring tension, but I could not find anyone around with a nut that would fit, also the rod seems to be very hard, I think it would be hard to thread it without a lathe, that has to be tried...

Don't forget to measure the valve spring in its original position, you have to put back the preload on it, otherwise things could get funny, a free flow or a valve not opening in the case you put too much preload ...

My QB is now disassembled and will remain this way until I can get access to the said chrony...

There is a good chance that this mod will make a non-pal QB over the 500 FPS, it is your responsibility to verify if it is the case.

While doing the mod, I also noted, with some few calculations that the biggest restriction to the flow is actually between the stem rod and the brass part of the valve, this is where there is the less surface area for the air to flow (see picture above). If you want or need more air to go through the valve, this is also something to look into, I did open up the valve (drilled) at that place and also drilled the transfer port. I now have a .25 and .30 barrel for the QB, that is why I did those mods, for now I plan to keep it below 500 FPS, I might, in time, mod it for more power to go hunting, but that will be another topic ;)

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Remember, always play safe with HPA and airguning in general, if you don't have a PAL, don't go over the limits and don't mod your toys if you don't feel completely safe while doing it, this will help to keep our leisure a good reputation!

I will be on vacations for a few days or more, if you post questions, it might take a few days before I reply, but I will. ;)


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PostPosted: Sun Jun 23, 2013 3:47 pm 
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Joined: Sun Feb 13, 2011 10:44 pm
Posts: 160
Louis

I like this mod in every way. What you have done here is good stuff and and it follows sound principals. It has never made sense to me to put a spring and associated retaining mechanism in the path of airflow. As far as structure goes putting the stem in tension and whacking it with a hammer is better than putting it in compression.

I think you should take this mod even farther and reduce the aluminum collar height to be the same as the threaded portionof the brass body. Then counterbore the brass body removing as much material as you can without risking the thread wall pulling apart. Of course you would need a small tool to tighten the "ring" and compress the Oring seal

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Sean


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PostPosted: Sun Jun 23, 2013 5:36 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
In the thread I discussed this idea a couple of months ago, I suggested that it may be possible to leave the aluminum sleeve on the valve all the time (glued or locktited) and just stretch the O-ring over the end and let it snap into the groove like is done in most valves.... I haven't pulled my new QB79 apart to confirm that is possible, but I'm guessing that at most a small tube spacer to hold the O-ring out in contact with the tube wall would allow the valve to be simply slid into place in the tube instead of having to tighten the two halves of the valve together after installation.... It works for a Disco, why not a QB, with (likely) a #113 O-ring....

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!


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PostPosted: Sun Jun 23, 2013 7:32 pm 
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Joined: Sat Jan 12, 2013 6:08 pm
Posts: 117
rsterne wrote:
In the thread I discussed this idea a couple of months ago, I suggested that it may be possible to leave the aluminum sleeve on the valve all the time (glued or locktited) and just stretch the O-ring over the end and let it snap into the groove like is done in most valves.... I haven't pulled my new QB79 apart to confirm that is possible, but I'm guessing that at most a small tube spacer to hold the O-ring out in contact with the tube wall would allow the valve to be simply slid into place in the tube instead of having to tighten the two halves of the valve together after installation.... It works for a Disco, why not a QB, with (likely) a #113 O-ring....

Bob

It should seal........
I was messing around with my 79 trying to fix a leak at the tank block. I forgot to tighten the valve down to 'squeeze' the o ring. The assembly was dunked in the bath and there were no leaks. I must point out the o ring on the valve was the OEM ring used in QB78 tube caps. Whatever spec they are, they seem to have a bit more cross sectional area to them. Does anyone know what spec they are. This may eliminate the need for a tube spacer bob?


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PostPosted: Sun Jun 23, 2013 8:53 pm 
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Joined: Sat Nov 03, 2007 4:19 pm
Posts: 8978
Location: Coalmont BC
The stock white QB O-rings are pretty hard, it's not surprising they "squeeze" them to get them to seal.... I plan to try just a 70D Buna N like I use in my other guns.... As long as the O-ring when installed in the groove with no crushing is touching the ID of the tube it should seal right up.... Once it makes the initial seal it tries to migrate into the outer back corner between the valve and the tube anyway....

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!


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PostPosted: Mon Jun 24, 2013 7:46 am 
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Joined: Sun Feb 13, 2011 10:44 pm
Posts: 160
Yes I do remember that now Bob

Louis there is an even better idea. permantently affix the ring with retainer and then dress the groove as need be.

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Sean


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PostPosted: Mon Jun 24, 2013 9:43 pm 
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Joined: Wed Mar 27, 2013 10:14 am
Posts: 4
Location: Somewhere in Quebec
Thanks Sean and Bob for your contributions, I agree with you both, this idea will have to be tried for sure, then it will be the "ultimate" QB valve! That mod ain't that hard to do, I believe many QB owners could do this by themselves, as long as one has the few tools required and a little patience, it's worth the time I'd say.

I'll probably be working more on this next weekend, till then, I'll be far in the wilderness with my little one, gone fishing yayy
XD


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