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PostPosted: Sat Aug 15, 2015 11:35 pm 
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Was wanting to play around with bulk filling the qb78...but didn't have the fitting. So made one. :)

Saw the idea of using a countersunk type screw and oring on one of the various forums in the past, but have never tried making it this way...figured it was a good time to try it out.

Works perfectly, and SOOOO easy to make. Haven't measured cracking pressure yet, but it's not much...can blow through it, so a couple psi or less. Tried it with the compressor first...seals @ 125psi and tested good at 1000psi too.

Might be old news to some, but thought it was interesting enough to share. :)

Image

Al


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PostPosted: Sun Aug 16, 2015 1:19 am 
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. . cracking . . couple psi or less. . . . seals @ 125psi . . . good at 1000psi too. . . .. interesting enough to share.[/.

Indeed!

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PostPosted: Sun Aug 16, 2015 7:34 am 
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Hand too clean.


I don't see in your pic how you bolt ot down, I read your post understand but pic does not go with your pic no bolt holes in fill valve.

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PostPosted: Sun Aug 16, 2015 9:26 am 
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I had a spare factory piercing plug assembly in the parts bin...I'm using the nut part to retain the plug. Just drilled it out a little.

FRANK wrote:
Hand too clean.


Will make sure I take a picture next time I change a motor...just for you Frank. :lol:

Al


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PostPosted: Mon Aug 17, 2015 12:51 am 
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You always amaze me and now I might even be interested. How many spares do you have?


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PostPosted: Mon Aug 17, 2015 4:40 am 
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Only made the one...but I think I heard that Lauchlin has a new lathe... :)

Al


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PostPosted: Tue Aug 18, 2015 12:28 pm 
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I think I need a QB to play with.


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PostPosted: Tue Aug 18, 2015 9:14 pm 
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Does anything stop the screw falling out, or is it held in place by the fill pressure? I've wondered the same thing about things like

Image

which looks like the check valve would just fall out and rattle around in the gas tube. How do you start filling something like that? Carefully? Vertically? :)


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PostPosted: Tue Aug 18, 2015 9:26 pm 
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EverHopeful wrote:
Does anything stop the screw falling out, or is it held in place by the fill pressure? I've wondered the same thing about things like

Image

which looks like the check valve would just fall out and rattle around in the gas tube. How do you start filling something like that? Carefully? Vertically? :)


Good question!?!?
I know when using adapters it is held in by those adapters.

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PostPosted: Tue Aug 18, 2015 10:01 pm 
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In the case of my HiPAC the aluminum rivet which acts as the check valve stem is held in place by a large plastic washer and a smaller one with a spring pushing those, the spring running the full length of the front section of tube and seating against the head of the next tube threaded in behind it. The spring is a little bit smaller than the tube ID. Seems overkill, filling up a fair bit of potentially usable volume just to press on a tiny rivet. I've been trying to think of a way to get rid of the spring and washers. But since in the case of the HiPAC the Foster nipple is part of the front section there's nothing to unscrew and modify there. With a screwed-in Foster fitting one could perhaps attach a small vented cylinder and insert a tiny spring into that to press on the poppet head...


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PostPosted: Wed Aug 19, 2015 6:40 am 
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EverHopeful wrote:
Does anything stop the screw falling out, or is it held in place by the fill pressure?

Screw is threaded in and snugged down. Filed a flat on the threads and slightly into the counter sunk portion for airflow.

I've wondered the same thing about things like

Image

which looks like the check valve would just fall out and rattle around in the gas tube. How do you start filling something like that? Carefully? Vertically? :)


Foster fill nipples are usually installed into a blind hole...the "stem" cannot fall out as it does not have enough travel in the blind hole. Opens by equalizing pressure on both sides of the seal, closes via flow creating differential pressure. Hold it just right and bleed the pressure slow enough and it won't close at all. A spring will close it, but then it will require a differential pressure to crack it open. The higher the cracking pressure, the greater the differential between what you think you put in...and what's actually in there. :wink:

Something like this can be used in an "open" hole as the guts are retained by a hex plug. Still doesn't seem to be spring loaded, so flow will be what closes it...

http://www.bestfittings.co.uk/shopexd.asp?id=182

Al


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PostPosted: Wed Aug 19, 2015 7:04 am 
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Ah, I see - that makes sense, thanks for the explanation.

Jim


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PostPosted: Tue Sep 01, 2015 11:06 pm 
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Still tinkering to get something up and running on bulk co2. Had an idea for the qb-ish pcp, and decided to use the bulk project as a test bed of sorts...

One of these things is not like the other....Sealed right up, no lapping or other fiddling required. 8)

Image

Think I'm going to have to break down the qb gopher gun and try this out.... :)

Al


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