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Help with Valve Disassembly

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Unread postAuthor: jrrdw » Tue Feb 12, 2013 10:36 am

Build a drum spanner. The outside dia. should just fit the port and a center hole to just fit over center shank, then 2 for bolts or steel dowels to fit the holes to turn out the part.

Have you tried turning it out through the front?
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Unread postAuthor: MrCrowley » Tue Feb 12, 2013 3:48 pm

If you have a vice..clamp 2 bolts in the vice ...really hard...
Take hex head bolts and put on enough nuts to create some mass for the vice to grip onto.
Turn them so the angles line up and clamp on the flat surfaces.

Make sure they fit into the snake-eyes..
Then put a pipe in the bottom of the Tee to use as a handle.
I had thought about this but the nail punches I were using kept slipping out because I had to wedge something in between them to get the right spacing but your suggestion sounds worthy of a try because I could probably find some nuts that will thread on to the bolts to give me the right spacing and enough surface area for the vice.

Clever, if the bolts wobble a bit they could be set in some softwood, and the wood crushed in the vice, to fix them properly.
My vice has a fairly small gripping face so I might grab two pieces of wood and stack the bolts in the vice vertically instead of horizontally (like above) as they would be less likely to slip out of the vice that way.

Have you tried turning it out through the front?

Don't think there's any way, I couldn't even get the valve to unseat by pushing on it.

With a better look, there seems to be a green substance on the plug, I'd sure it's loctite. Over such a large area, it'll be pretty tough to shift.
Good eye, didn't think about that.


So I think I have a few options that should all theoretically work, I'll start work on it shortly :wink:
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Unread postAuthor: MrCrowley » Tue Feb 12, 2013 7:13 pm

Well I got it open. I drilled bigger holes to poorly threaded a bolt in each hole (without a tap) and then used a big plumbing wrench to grip both bolts and unthread the plug.

I was thinking from the outset that the valve could possibly be used for a piston hybrid cannon but the uncommon internal threads makes it difficult. The plug/end cap thread is a touch smaller than 1.25" N.B. galv. iron thread and the thread for the removable valve seat is a touch over 1" N.B. galv. iron thread.
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Looking through the back port towards the front port (the o-ring is where the removable seat threads in and seals against):
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Last edited by MrCrowley on Tue Feb 12, 2013 8:05 pm, edited 1 time in total.
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Unread postAuthor: Zeus » Tue Feb 12, 2013 7:59 pm

I'll give you $12.50 plus postage, that's the best I can do.
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/sarcasm, /hyperbole
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Unread postAuthor: MrCrowley » Tue Feb 12, 2013 10:42 pm

Haha I'm sure I'll find a use for it. It would probably cost three times as much as your offer just to post it, it's really quite heavy.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2013 1:58 am

That's a quality part, deserves to be in something dramatic :)

Also, what's a sample cup doing on your workbench?
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Unread postAuthor: MrCrowley » Wed Feb 13, 2013 2:47 am

That's a quality part, deserves to be in something dramatic

Any ideas? Clearly, the valve doesn't have flow in mind as the 'piston' does its best to take up as much space as possible (being square instead of circular), leaving only a small amount of room around it for gases to escape around. Though, I think there's some way I can make it useful if I remove the piston, spring, and bolt thingy and make something else myself.

what's a sample cup doing on your workbench?
Haha that's for my microscopy; once a collection jar now a killing chamber. I drilled a hole in the top so that smaller sample tube can sit in the lid, I superglued that in and poked a hole through the bottom of the small sample tube. Now I can put insects inside the collection jar, open the sample tube lid to put a few droplets of isopropyl alcohol in the sample tube and wait for it to evaporate through the hole and in to the collection jar killing whatever was inside :D

My previous method of putting an insect in the jar with a few drops of 99% alcohol usually ended up with the insect being covered in alcohol, which can ruin the specimen for later inspection and probably isn't very nice for the insect either.
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 13, 2013 4:14 am

MrCrowley wrote:Any ideas? Clearly, the valve doesn't have flow in mind as the 'piston' does its best to take up as much space as possible (being square instead of circular), leaving only a small amount of room around it for gases to escape around. Though, I think there's some way I can make it useful if I remove the piston, spring, and bolt thingy and make something else myself.


If I got the configuration right, it would make a killer HPA auto pop-off...

My previous method of putting an insect in the jar with a few drops of 99% alcohol usually ended up with the insect being covered in alcohol, which can ruin the specimen for later inspection and probably isn't very nice for the insect either.


Use ethanol, death by booze :D shame you're not local, we use thousands of litres of ethyl acetate every year.
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Unread postAuthor: MrCrowley » Wed Feb 13, 2013 7:00 pm

jackssmirkingrevenge wrote:If I got the configuration right, it would make a killer HPA auto pop-off...
Well you were right about that. When I bought it I thought it wouldn't make a great pop-off because of the low flow but I just tried it at 160PSI and 240PSI and I'm quite impressed. With only my track pump hooked up to the inlet it would pop at 160PSI and re-seal extremely quickly at ~140PSI, even though the volume of air from the pump's check valve to the relief valve inlet wouldn't be much more than a tablespoon's worth.

It's also very easy to adjust and you can do it without a spanner as the end cap's o-ring proves adequate when tightening by hand. I think the valve was originally set at 250PSI (with a maximum of 300PSI according to the spec sheet) but I adjusted it as far as it could go and it didn't show signs of popping at 320PSI.

I think it would probably only be useful for shooting light projectiles like paintballs because it only releases a small volume of air. Though, you could always use another spring or add some spacers to up the pop-off pressure and use it with unregulated CO2. The only worry might be the plastic sealing face but that could be replaced with something that doesn't mind cold temperatures too much.
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 14, 2013 2:00 am

MrCrowley wrote:I think it would probably only be useful for shooting light projectiles like paintballs because it only releases a small volume of air


Keyword - HPA. Remember that in commercial PCPs only a tiny volume of air is released per shot. Just because it pops at say 300 psi, it doesn't mean you can't feed 600 psi from the trigger valve.

Since you like to work in bigger scales, you could use it as a pilot for an automatic golfball launcher on steroids...
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Unread postAuthor: MrCrowley » Thu Feb 14, 2013 2:58 am

Remember that in commercial PCPs only a tiny volume of air is released per shot.
True, but this valve is probably too big for anything smaller than 10mm in calibre and too small for anything larger than 25mm in calibre. It also weighs something like 3.4 pounds IIRC.

Maybe I could make a full-auto paintball (or ping-pong) gun with it but I still need to sort out a cheap (but decent quality) high pressure gauge and regulator for my CO2 bottle and fridge compressor setup. I've seen those cheap aquarium regulators on eBay but they only output to pressures under 200PSI where I need 300PSI minimum.

Just because it pops at say 300 psi, it doesn't mean you can't feed 600 psi from the trigger valve.
Do you mean to imply that you can still get the benefit of 600PSI or that simply you can run your air source at a higher pressure than what the valve pops at? If you meant the former, wouldn't the valve either pop at 300PSI and re-seal if the flow from the air source was too low, or pop at 300PSI and stay open because the flow from the air source is high enough that the 600PSI in pressure keeps the valve open?

Since you like to work in bigger scales, you could use it as a pilot for an automatic golfball launcher on steroids...
If only my dwelling and income were much larger than their current standings :(

Also, I just remembered that this valve is meant for refrigerants and can probably handle cold gases quite well.
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 14, 2013 3:16 am

MrCrowley wrote:Do you mean to imply that you can still get the benefit of 600PSI or that simply you can run your air source at a higher pressure than what the valve pops at? If you meant the former, wouldn't the valve either pop at 300PSI and re-seal if the flow from the air source was too low, or pop at 300PSI and stay open because the flow from the air source is high enough that the 600PSI in pressure keeps the valve open?


I'm assuming you have a high pressure source, connected to a trigger valve (say ball valve or pressure washer valve) then connected to this valve as a pop-off.

You don't need a regulator because no matter what pressure you're feeding, the valve is going to pop at the same pressure. Obviously if you're feeding from a source much higher than the pop-off pressure, then the buildup is going to be very fast, so you need a low flow valve in order to keep the cyclic rate managable.
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Unread postAuthor: MrCrowley » Thu Feb 14, 2013 5:49 pm

You don't need a regulator because no matter what pressure you're feeding, the valve is going to pop at the same pressure
Ah, I see what you mean. I guess I don't need a reg but I'm going to wait until I can pick one up as I have a few other projects in mind that are waiting for a HP reg and having a reg on a cannon using this valve allows me to be a bit more creative with the trigger valve as I don't have to find one rated for high pressure.
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