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Pvat V2.0

The VenPVAT

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#1 venom213

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Posted 13 March 2011 - 01:10 PM

Instead of naming this simply PVAT V2.0 I decided to add an alternate title, the VenPVAT (pronounced Ven-pee-vat, with a Russian accent of course).

My overall objective with this was to make Lt. Stefan's PVAT more robust and easy to disassemble/reassemble.

First, I took a small piece of 1/2" SCH80 PVC and 3/8" ID PEX Tubing. I wrapped electrical tape around the SCH80 until it fit snugly in a 1" Threaded PVC Plug. I then wrapped electrical tape around the PEX until it fit snugly in the SCH80. This is to make the hole I drilled as centered and perpendicular as possible. I drilled down the PEX with a 3/8" Drill bit and continued through the plug.

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Once the hole is drilled, tap it with a 1/8-27 NPT Tapping Bit.

Next, I took a 1/8" NPT Nipple (the kind with the hex center) and a 1/8" NPT Nut. I applied Plumber's Goop to one end of the nipple and threaded it in to the PVC plug as far as it would go. I then used needle nosed pliers to thread the nut onto the nipple where it protruded into the inside of the plug.

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I proceeded to take a 1/8" NPT Cap and Drill a hole in the end of it slightly larger than 1/4". The inside of the cap is already dimpled where the center is so the drill bit should be guided fairly well by that.

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Here's the new rear sealing set up. It is 2 3/16" ID 5/16" OD O-rings. There is a third one there (1/4" ID 3/8" OD) but I ended up not putting it on so ignore it. The idea is that the O-rings are sandwiched between the nipple and the cap so that they have nowhere to move but they can still be adjusted by taking apart the cap and nipple.

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Lube up the carriage bolt, but the cap on it, and put the O-rings on it (again, ignore the third O-ring). Put goop all around the O-rings and on the end of the nipple. Thread the cap and nipple together using two wrenches, thus sandwiching the O-rings between them.

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Make sure the bolt can still slide through and it is not being glued in place as well. It should look like this

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While that is drying you can assemble all of the other internal parts. Mine is pretty much the same as Lt. Stefan's, but I added some nylon spacers because my spring wasn't quite long enough. The assembly goes Spacer-Spring-Spacer-Nut-Nut-Washer-Nut. The spacers are 1/4" ID 1/2" OD. The nuts are 1/4-20. The Waher is a 5/8L beveled faucet washer. The hole in the washer must be expanded with a 1/4" Drill Bit to fit on the bolt.

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Cut a 2 1/4" Piece of 1" PVC. I used thinwall, but I doubt it makes much of a difference. PVC cement this piece between a 1" Coupler and a 1" to Female Adapter. Also, cement a 1" to 1/2" Reducer into the other end of the 1" Coupler.

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I needed a way to get air into the tank of course. I chose to use the method Whisper101 posted, but there are many other options. Drill a 3/8" Hole into the side of the adapter. Tap it with a 1/8-27" Tap.

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Now you can thread in whatever 1/8" NPT fitting you want. An example is a 1/8" NPT to 1/4" OD Quick Connect. I decided to go with a 1/8" NPT to 1/8" Hose Barb because I needed the other fitting for another project. I gooped in the adapter, but Teflon seal tape can keep it sealed fine as well.

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Edited by venom213, 13 March 2011 - 02:39 PM.

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#2 venom213

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Posted 13 March 2011 - 01:12 PM

Once all the goop and solvent weld has cured, I finally put everything together. To seal the 1" plug, I applied 3-4 layers of Teflon seal tape around the threads of the plug. I then used a vise and a large wrench to thread the plug into the adapter. The purpose is that by using threaded parts and teflon tape, the tank can be disassembled by unscrewing the pieces. Reassembly is simple as well, simply apply a new wrapping of teflon tape and thread it back in.

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The end product.

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With a hornet pump.

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A few notes: I did the water test for leaks on this, I didn't see any with the final product. I ended up going back and adding longer nylon spacers so the spring would compress more. It needs a fair amount of compression to seal the washer properly. I applied silicone grease to the front of the washer to improve the seal as well. I will most likely be building a few variations of these, making test videos, and offering them for sale shortly.

Edited by venom213, 13 March 2011 - 02:38 PM.

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#3 ahtanie

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Posted 13 March 2011 - 01:22 PM

Very nice, Venom.
I'm a huge fan of airguns so this is very appealing to me.
Add one of your adjustable OPRV pumps to it and you have an entire homemade pump + tank setup.
Great work as of late, keep it up! :)
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#4 TantumBull

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Posted 13 March 2011 - 03:47 PM

You shouldn't even keep the name. This is superior in every single way to the original.
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#5 thedom21

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Posted 13 March 2011 - 03:52 PM

I think you are making a completely homemade air gun with the homemade pump, orpv, and now this.
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Funny Irc moments

22:32 hookerninja I would just switch to 2 full 69's
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#6 Hipponater

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Posted 13 March 2011 - 04:07 PM

You shouldn't even keep the name. This is superior in every single way to the original.


Exactly this.

I'm very interested to see where this goes, good stuff!

What's the estimated cost of one of these, if you don't mind?
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#7 Daniel Beaver

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Posted 13 March 2011 - 05:54 PM

That's totally banned at the war.

Wait.... Minnesota doesn't ban homemade air-guns.....

AAAAAWWWWW YEEEEEAAHAHHHHHHH
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#8 WicketTheModder619

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Posted 13 March 2011 - 07:02 PM

That looks very cool. Great job with all of these homemade components lately!
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23:06 Buffdaddy: As long as they aren't doing it all night, don't care.

#9 utahnerf

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Posted 13 March 2011 - 09:55 PM

Looks very good, especially the pin assembly. Lookin' flossy.
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#10 MavericK96

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Posted 14 March 2011 - 12:50 AM

Having put together a couple PVATs myself, I like this design. Seems like it's easier to assemble and seal than the original design. Nice work.
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#11 Draconis

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Posted 14 March 2011 - 02:11 AM

That's totally banned at the war.

Wait.... Minnesota doesn't ban homemade air-guns.....

AAAAAWWWWW YEEEEEAAHAHHHHHHH



Why isn't there a like button for comments? :)

Venom, this looks awesome, though about the size of a 5K tank. Is that correct?
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[15:51] <+Noodle> titties
[15:51] <+Rhadamanthys> titties
[15:51] <+jakejagan> titties
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[15:51] <+Gears> titties
[15:51] <@Draconis> Titties.
[15:52] <+Noodle> why is this so hard?

#12 Ozymandias

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Posted 15 March 2011 - 03:51 AM

Why isn't there a like button for comments? ;)


Planned Moderation System, from Dec 4, 2002.
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If you wish to post anything HvZ related, here ya go.

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#13 ChaosPropel

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Posted 15 March 2011 - 08:27 PM

The only thing that's making me hesitant of completely following your design is the 1/4" hole to be drilled in the 1/8" cap. I've never worked with air gun fittings (I'm more of a springer guy, but I'm trying to start getting into air guns), so excuse me if I'm making a rookie mistake.....

How hard would it be to drill through the cap? Could I do it with a normal hand drill?

Other than that, great job!
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Preheat oven to 350 degrees F (175 degrees C).

#14 NerfGeek416

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Posted 15 March 2011 - 08:32 PM

If you mean a hand drill, than no. A drill will work fine, if you are worried about needing a drill press. You might want to hold the cap in a vice though.

Edited by NerfGeek416, 15 March 2011 - 08:34 PM.

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#15 utahnerf

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Posted 15 March 2011 - 09:07 PM

You could use a variety of methods, as long as you end up having the hole in the cap. Personally, I use my drill press, but before I had one I used an electric hand drill. You don't even need a vise, I used to have my brother hold the piece with pliers while I drilled. So yes, you can use a hand drill, just be careful so that the piece doesn't start spinning around.
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#16 ChaosPropel

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Posted 16 March 2011 - 05:51 AM

You could use a variety of methods, as long as you end up having the hole in the cap. Personally, I use my drill press, but before I had one I used an electric hand drill. You don't even need a vise, I used to have my brother hold the piece with pliers while I drilled. So yes, you can use a hand drill, just be careful so that the piece doesn't start spinning around.

Got it. Thanks!
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Preheat oven to 350 degrees F (175 degrees C).

#17 utahnerf

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Posted 18 March 2011 - 11:22 PM

Is it possible that you could make a video of the mechanism/firing/ranges?

Edited by utahnerf, 26 March 2011 - 02:18 PM.

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