Moding a QEV
For a repeating pneumatic I plan on using a QEV. I have heard that for them to repeat a hole on the piston/diaphragm and a spring is required. I think I have the spring part down but, I'm having trouble getting my head around the need for the hole. I would appreciate it if someone would explain the purpose . (I'm using a 1/2" deltrol diaphragm QEV from McMaster Link)
Last edited by irisher on Tue Apr 27, 2010 6:00 pm, edited 1 time in total.
- jackssmirkingrevenge
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If you're filling from the pilot side, you don't need an equalisation hole, but if the air is coming from the chamber side, you need a hole to let air get in behind the piston/diaphragm, and the spring allows this to happen without it firing.
hectmarr wrote:You have to make many weapons, because this field is long and short life
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Well, almost everybody fills through the pilot, and nobody mods it, so if you gonna fill through pilot, no.
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Just make sure that your pilot valve has a much better flow than the connection you're feeding through, otherwise it will never fire...irisher wrote:So if I am filling through pilot I need no modifications?
hectmarr wrote:You have to make many weapons, because this field is long and short life
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To prevent messing up a good QEV, use and aquarium or other needle valve and place this external to the QEV. The advantage is it is adjustable unlike a hole in the piston.
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if your making it like polands gun thay you dont need to mod it at all
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It has a large onboard air tank that will be replenished from an outside airsource.The problem is, if the entire tank is dumped each shot then I will not have enough flow to fill it up before the next shot. If I can not get a QEV to repeat with the 3-way and pilot side filling then my design needs some serious revision.
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a QEV + 3way will work and you will not need to mod it at all.
that is why poland like the 3 way idea no need to mess around with your QEV and its more air efficient than a QEV+pop off
that is why poland like the 3 way idea no need to mess around with your QEV and its more air efficient than a QEV+pop off
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I just want to stress the fact that in real life QEVs are normally used with 3 way valves... QEV stands for Quick Exhaust Valve
they are used to speed up return spreed of a single acting air cylinder... single air cylinders are normally controlled with a 3 way valve.. so in other words:
QEVs were designed to be used with 3 ways
you can calculate how much time it takes to fill the chamebr to x pressure if you know the flow of the valve you want to use...
unless you want to build a fullauto gun that uses a lot of air for each shot this shouldn't be a problem
they are used to speed up return spreed of a single acting air cylinder... single air cylinders are normally controlled with a 3 way valve.. so in other words:
QEVs were designed to be used with 3 ways
what sort of pressures and volumes are we talking about ??if the entire tank is dumped each shot then I will not have enough flow to fill it up before the next shot.
you can calculate how much time it takes to fill the chamebr to x pressure if you know the flow of the valve you want to use...
unless you want to build a fullauto gun that uses a lot of air for each shot this shouldn't be a problem
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I plan on Co2/HPA system but, it would be nice for it to work on a fridgy or normal air compressor. Here is my setup with AA for size comparison.what sort of pressures and volumes are we talking about ??
Problem is I want a full-auto gun. Although I don't mind having low amounts of air per shot.unless you want to build a fullauto gun that uses a lot of air for each shot this shouldn't be a problem