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Hi, I am new here but I have some experience in building pneumatic spudguns (mostly 1/2 inch steel pipes and fittings and i normally pump them to 250 psi). However the problem is that so far I've been using ball valves. I've read that QEVs have better performance but I have some questions for you first:
1. Does 1/2 qev has higher flow than 1/2 ball valve ??
2. As far as i know most QEV's are rated to 10 bar (150 psi) are there any QEVs that can hold more ? (like up to 300 psi).
3. What would happen if I used a QEV rated to 150 psi with higher pressures 200 - 250 psi? I mean would it be safe and working properly ?
4. How durable are QEV's ? I've seen some pictures of them and I know that most of them are made from some alloys - I mean wouldn't they get dammeged because of the stress caused by the weight of 50 inches long steel barrel and chamber ??
1. it probbly has about the same flow, but it opens much fast, therefore it is more powerful.
2. it think they only go to 150
3. no it wouldnt be safe, but people have done it.
4. they are very durable, but i would make a suport for it.
"physics, gravity, and law enforcement are the only things that prevent me from operating at my full potential" - not sure, but i like the quote
you know you are not an engineer if you have to remind yourself "left loosy righty tighty"
I have been using QEVs for about 3 years now and i have never had problems with using them above their suggested pressure rating.
1: Less flow than a fully open 1/22 BV but WAY faster opening times resulting in much more power.
2: There are QEVs that are specifically rated to 400PSI, but I have taken my Detrol QEVs up to 400PSI on many occasions and they didn't fail. It does not mean they won't ever fail, but from personal experience they have held up fine.
3: I would work properly. The diaphragm may pop on a 'phram QEV, but nothing will happen the the alloy body of the valve.
4: They are very durable. But having a 50" barrel might put some stress on it, so I would advise on adding a barrel/chamber support to even the stress a bit to reduce the chance of failure.
Good luck getting 50" of 1/2" chamber to 200-250 PSI. It would take you about a weeks worth of pumping. If you want to use high pressure, use a small chamber to make up for lost chamber volume.
1. It has lower maximum flow, but a ball valve opens so slowly that a QEV is many times more powerful.
2. You can get high pressure variants of many things, but it will cost a lot more.
3. It can be "safe". I've done/I do such a thing. It works fine, perfectly as normal, and it has not yet shown a single problem.
It is unlikely to fail, but if it does, you can't hold anyone responsible other than yourself if it does.
Using a 150 QEV within a reasonable limit above it's rating will not stop it working, and it is probably safe, but don't come to me complaining if it explodes.
If you do exceed the rating, you'll need to be VERY careful.
4. They are durable enough, but as hi said, a support would be wise.
I use a chamber 4 times that size at a greater pressure (320 psi), and it only takes a few moments to pump, but I do have a custom mid volume high pressure pump specially for that purpose.
50" of 1/2" isn't that bad. That's about a foot of 1", which is perfectly reasonable for a shock pump user to fill in a few minutes, but towards the higher end of what I'd want to consider.
well it takes me about 1,5 minute to 50 inches long chamber with my ghettocompressor
Sorry for offtoping but I've read that many people have some problems with pumping their spudguns - has anyone ever suggested here to use this:
It is a part of a refrigerator ( I mean that white thing that is standing in most kitchens ) I use it myself and it can pump up to 300 psi easily. Ofcourse it has smaller flow than 'normal' comercial compressors.It is cheap (you only need an old refrigator and you can even easy to build and safe.
That compressor is not designed to pump air but a refrigerant. Problems may result.
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Before anyone gets too many ideas, the process of removing removing a pump from an old fridge will release gases harmful to the ozone layer. I probably would have raided for one before now if this weren't the case.
Mr Crowley might get his global warming wish if enough people try this without due care and attention.
However, I have heard of them being used. Very quiet, which would be a nice thing compared to a lot of compressors.
The trick is to inhale all the freon so it doesn't hurt the ozone layer
but in all seriousness, how well does it work anyway?
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well i havn't encountered any problems so far. My compressor looks rather strong - it has thick metal casing/frame that looks capable of using higher pressures than 300 psi but I've limited myself to 300 for safety reasons. BEsides this thing is rather small so if you are afraid that it might burst or something you can always dig a hole in your backyard and put it there whenever u use it
It can pump to 300 psi (at least mine can) it is quiet but it has lower flow than 'normal' compressors. Most of these pumps (I have no idea wheather you have the same type used in US) are enclosed in thick metal casing/frame (I suppose it is filled with oil or something) and there are 3 thin copper pipes sticking out of them (only two of them are important - one should be already sealed/fastened). One pipe is an air intake and the other is where the air comes out. Obviously there isn't any tank nor safety valve in it unless you add it yourself.
to be honest it does release freon (harmful to the ozone layer) when you remove them
But you can buy them on the internet - the pump is offered as a spare part or something - so it can be used without harm to the enviroment.
Does anyone know where i can find them ?
Last edited by POLAND_SPUD on Sun Nov 04, 2007 6:17 pm, edited 1 time in total.
The QEV I bought is a 3/8 inch one. It has a nickle coated steel body. It has no markings or pressure ratings on it. I take it to 180 easily. Hell it can probably take more.
But I would probably limit myself to 200 psi on a gun. Not sure about large ones but Im sure they are equally proportioned so would probably be the same.
I think British QEV's can be rated to 300psi.
Ha yeah, though I was hoping it would be the Carbon Monoxide gases released from incomplete combustion in a combustion spudgun not a fridge compressor
LOL, put a balloon on the end and.... What then? Did you ever think about what happens when the fridge get thrown away? Probably don't get recycled in most areas...
I get the feeling that one or two old refridgerators don't contain enough CFCs to burn a hole in the ozone layer.
"If at first you dont succeed, then skydiving is not for you" - Darwin Awards
But that would be an indicator of poor efficiency! And it would also imply that people were using combustions over pneumatics...
I've never really liked combustion. My last combustion was built well over a year back, nothing more than a basic spray 'n' pray*.
Still fun to use, but in spite of it's size, it's outperformed kinetically by HEAL by a large amount.
UK QEVs are rated to 150 normally, but they've been tested and declared safe at 300 psi.
There are regulations on fridge disposal, which cover recycling, as well as door removal (Kids have been known to try hiding in them and suffocate.)
@Turbosuper: Would you care to correct that statement?
CFCs are seriously bad. They act as a catalyst, not a reactant. One litre of CFC can destroy many cubic metres of ozone. In theory, one molecule of CFC could completely annihilate the entire ozone layer, although it would take a long time.
It's irresponsible to think: "Hey, if I do it, it makes no difference". All it takes is enough people to think that, and it snowballs.
*(Where did that originally come from? I don't remember seeing it being used for spudding before a few months back, and I've been reading around forums for quite a while.)
Well even if you do have a metered setup, it will probably still be slightly inefficient and let of small amounts of CO. I never really liked them either, I've only built a basic spray and pray as well.
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