Simple Valve Design

[Rand0mK1w1]

Hi!

I'm looking to make my first 'real' Air rifle (one that doesn't use a ball valve)

I don't really want to us a modded sprinkler valve or a QEV on ebay (because its too expensive), and I dont trust myself to make a homemade QEV, therefore I made my own design for a simple valve.

Can someone tell me why this design for a simple valve wouldn't work?

The actual air rifle is only pumped to 100psi but everyone at other forums keeps saying that this wouldn't for some reason but failed to tell me why.

Stage one

In stage one there is basically the air chamber to the left but the air cannot get through because of the (red) endcap sealed against the rubber washers (black).

Stage two

The trigger connected to the red pipe and endcap is pulled manually and therefore pulls the whole red structure (plus the rubber washers) backward exposing the hole made in the red pipe so air can travel through it and out the barrel.

Sorry if I sound like a complete noob but I have not much experience with this stuff.

Thank you

[jackssmirkingrevenge]

I don't really want to us a modded sprinkler valve or a QEV on ebay (because its too expensive)

Seriously?

$10 posted is too expensive?

Hmmm...

Can someone tell me why this design for a simple valve wouldn't work?

It will work, but:

1) You're pulling the trigger against the air pressure. Let's say you're using an airsoft barrel with a 7mm outside diameter. This means that at 100 psi, you're pulling against a force of around 6 lbs, which is not inconsiderable.

2) The opening speed is entirely dependent on how quickly you pull the trigger, so consistency and therefore accuracy will be hard to achieve.

It can be improved by making the barrel/valve system "balanced" but this would involve several dynamic seals which would be out of your apparent construction/budget restrictions.

[mattyzip77]

Seriously...... you can get a qev on ebay for 10 bucks or less....not expensive at all.......

[Rand0mK1w1]

Seriously...... you can get a qev on ebay for 10 bucks or less....not expensive at all.......

Well since I'm not near America or England it's $10 plus shipping usually equaling to about $20 - $40 so I might as well just mod a $20 sprinkler valve from my local hardware store. I've tried looking for free shipping but usually if it is free they bring up the price

[Rand0mK1w1]

I don't really want to us a modded sprinkler valve or a QEV on ebay (because its too expensive)

Seriously?

$10 posted is too expensive?

Hmmm...

Can someone tell me why this design for a simple valve wouldn't work?

It will work, but:

1) You're pulling the trigger against the air pressure. Let's say you're using an airsoft barrel with a 7mm outside diameter. This means that at 100 psi, you're pulling against a force of around 6 lbs, which is not inconsiderable.

2) The opening speed is entirely dependent on how quickly you pull the trigger, so consistency and therefore accuracy will be hard to achieve.

It can be improved by making the barrel/valve system "balanced" but this would involve several dynamic seals which would be out of your apparent construction/budget restrictions.

Ah ok now I've got a better understanding thanks.

Just asking with your model how would you keep most of the moving parts air tight?

I see the washers but if they're not pressing against anything won't the air just squeeze past them?

Once again sorry if I sound like a noob

[jackssmirkingrevenge]

If it's made the right size, the o-rings would not allow air past them.

By the way, with the design you proposed you would get about the same performance as using a common shop blowgun as a main valve. The blowgun body would also serve as the air chamber. This would be a good route to take if you have a limited budget and tool/material resources.

Here are some projects that might provide some inspiration:

http://www.spudfiles.com/forums/15-high ... ter,0.html

http://www.spudfiles.com/forums/airsoft ... ter,0.html

After that you can invest in a shock pump which will allow you to go to 200-300 psi and give you much better power.

[Brian the brain]

Randomkiwi and JSR...

Both your idea's combined seems like it would just about work best.
But instead of two O-rings I've replaced one by a flat washer to prevent wear and snagging from the O-ring having to pass a hole.


In this configuration you could take: a 15mm brass ( solder) endcap.
Drill a small hole to allow a 6mm bolt to be inserted.
Slip a section rubber hose over the bolt from the other side and slip on a nut, wich you filed down to fit inside a 12mm copper tube.

Slide a 12mm solder ( straight) coupler onto a 12mm pipe and press the endcap with the rubberhose thing over the end.
Turn the 6mm bolt to compress the rubber hose.This bolt will keep the pipe fixed to the endcap.Turn in the bolt as far as it will go.


Roll an O-ring over the pipe, leave it on the coupler touching the endcap


This is how you make the bolt/piston assembly.
You will need to cut/drill the transferport.
If the travel of the piston and barrel is big enough, you could use a T fitting to feed the ammo through the transferport .


This assembly will be pushed open when pressurised, so hook it onto a trigger.
Pull trigger to release.
If you have trouble making an adjustable trigger ( so it actually seals the piston!) I'll help you.

another way ( probably simpler!) would be to control the pressure is to feed this valve through a blowgun and make the springcompression adjustable to control the pressure at wich the valve pops open...


A note to JSR: An airtight shroud around the barrel, some ventholes in the barrel near the muzzle and a channel to the volume behind the piston would do..??
I think this coiuld be done with good old regular fittings , a strong spring and high pressure...

[jackssmirkingrevenge]

As drawn the pressure would seem that it would pop it back once it cracks open a little .... but for a n00b it might be a frustrating project, hence my blowgun suggestion.

[Rand0mK1w1]

If it's made the right size, the o-rings would not allow air past them.

By the way, with the design you proposed you would get about the same performance as using a common shop blowgun as a main valve. The blowgun body would also serve as the air chamber. This would be a good route to take if you have a limited budget and tool/material resources.

Here are some projects that might provide some inspiration:

http://www.spudfiles.com/forums/15-high ... ter,0.html

http://www.spudfiles.com/forums/airsoft ... ter,0.html

After that you can invest in a shock pump which will allow you to go to 200-300 psi and give you much better power.

Thanks for that suggestion! if blowguns work just as well i guess i'll just use a blow gun!

now trying to find a blowgun in Australia, snap!
Ebay

[Rand0mK1w1]

Randomkiwi and JSR...

Both your idea's combined seems like it would just about work best.
But instead of two O-rings I've replaced one by a flat washer to prevent wear and snagging from the O-ring having to pass a hole.


In this configuration you could take: a 15mm brass ( solder) endcap.
Drill a small hole to allow a 6mm bolt to be inserted.
Slip a section rubber hose over the bolt from the other side and slip on a nut, wich you filed down to fit inside a 12mm copper tube.

Slide a 12mm solder ( straight) coupler onto a 12mm pipe and press the endcap with the rubberhose thing over the end.
Turn the 6mm bolt to compress the rubber hose.This bolt will keep the pipe fixed to the endcap.Turn in the bolt as far as it will go.


Roll an O-ring over the pipe, leave it on the coupler touching the endcap


This is how you make the bolt/piston assembly.
You will need to cut/drill the transferport.
If the travel of the piston and barrel is big enough, you could use a T fitting to feed the ammo through the transferport .


This assembly will be pushed open when pressurised, so hook it onto a trigger.
Pull trigger to release.
If you have trouble making an adjustable trigger ( so it actually seals the piston!) I'll help you.

another way ( probably simpler!) would be to control the pressure is to feed this valve through a blowgun and make the springcompression adjustable to control the pressure at wich the valve pops open...


A note to JSR: An airtight shroud around the barrel, some ventholes in the barrel near the muzzle and a channel to the volume behind the piston would do..??
I think this coiuld be done with good old regular fittings , a strong spring and high pressure...

Hey thanks heaps for all that! thing is i'd probably stuff it up somewhere down the track so I guess for now ill just use a blowgun or a sprinkler valve with manual of/off bleed lever.

Thanks again!

[jackssmirkingrevenge]

http://www.spudfiles.com/forums/semi-au ... 23626.html

Less than $20 posted.