22 replies to this topic

[Trashmouse]

Hello everybody. I've been trying to build an airgun recently and i've gotten stuck at the trigger. 

I dislike how a ball valve feels and looks, but i don't have the money for one of those fancy mjvo-3 valves.

Any ideas/tips for what i can use as a trigger mech?

[GensoNerf]

You could try to make a homemade version of a Big Blast release mechanism.  A descent hardware store should provide the proper PVC and other parts.  If that would end up being a more costly solution, you could always just save money to buy the mjvo-3 valves.  

 

Aside from that, I suggest just walking up and down the aisles of your local hardware stores(assuming you have more than one) and try to get ideas from that.

[blitz]

Build something like this. Lowes and other hardware stores sell different check valves (the only ones I have access to are threaded, which is annoying) but making one of these is totally doable. Trigger, tank, pump, RSCB all in one compact package. 

http://nerfhaven.com...-the-mad-ghost/

[thedom21]

WNTS or just a pvc check valve with the rod extended works great.

Edited by thedom21, 23 July 2017 - 10:27 AM.

[laser]

the MJV0-3 is your best bet for a homemade airgun

[Ice Nine]

The MJVO-3 is a great valve, but it's really only useful for very specific builds of homemade airguns. You couldn't just "substitute" it into a build where you were going to use a ball valve as a trigger and have it work. It sounds like you had a specific design direction in mind; do you mind sharing details so we can better help you out?

 

I would second Blitz's suggestion of the Mad Ghost design using a PVC check valve, though, if you're not dead-set on something specific yet. There are also solenoid valves (like the one used in cxwq's BAMF design) that have manual bleeds that work like a ball valve but are much more ergonomic.

[Trashmouse]

The MJVO-3 is a great valve, but it's really only useful for very specific builds of homemade airguns. You couldn't just "substitute" it into a build where you were going to use a ball valve as a trigger and have it work. It sounds like you had a specific design direction in mind; do you mind sharing details so we can better help you out?

 

I would second Blitz's suggestion of the Mad Ghost design using a PVC check valve, though, if you're not dead-set on something specific yet. There are also solenoid valves (like the one used in cxwq's BAMF design) that have manual bleeds that work like a ball valve but are much more ergonomic.

I've mostly been looking at http://nerfhaven.com...ade-airgun-v10/ Which is your build Ice, but i haven't really built anything myself yet. 

I've been drawing and thinking of ideas because I'd rather not spend money on something that won't work. 

But the QEV blaster and the Madghost seem like what i want to make, which is a compact but decently powerfull air blaster

[Ice Nine]

I've been drawing and thinking of ideas because I'd rather not spend money on something that won't work. 

But the QEV blaster and the Madghost seem like what i want to make, which is a compact but decently powerfull air blaster

 

If cost is really a major concern, then building a Mad Ghost-style design is probably the best choice. The biggest challenge is making the trigger mechanism seal, and in the worst case where it doesn't, all you'd need to do is buy another 1/2" PVC tee/elbow. The fittings for a QEV blaster, even if you do it as cheaply as possible via Amazon products, are way more in cost without even including the MJVO-3.

[shmmee]

If you're willing to consider using a back pressure style of tank (panther, xbz, big salvo, hornet...) you should be able to modify a shcrader valve stem from a bicycle tire inner-tube. simply pushing in the pin will vent the fill line to the tank and fire the tank. The threads on the valve stem might be useful for mounting the valve and you could also cut out some of the thread wall to guide a trigger bar over the schrader valve. You can also stretch some vinyl tubing over the back of the valve if you warm up the tubing first with a hair dryer (maybe), heat gun or carefully with a flame and double wrap a zip tie to seal it.

 

You might also want to consider the slightly less expensive MAVO-3. the cfm's are a little less but i've used them successfully on many of my air tank builds so they've proven sufficient for stock nerfy tanks (just keep the air line between the pump, trigger valve and air tank to a minimum. The shorter that line is, the faster it can vent and the sharper the tank's air release will be.

 

I don't know if the mjvo-3 will shut off the inlet before back venting the outlet but the mavo-3's will - which means they can be used to make a true semi auto. (they won't vent off your reserve tank with each trigger pull.)

 

https://www.amazon.c...keywords=mavo-3

Edited by shmmee, 26 July 2017 - 08:42 AM.

[jamesp]

I hate to resurrect a 6 month old post, but this is the most recent post that pertains to my issue.

I put together my Mad Ghost (thanks to 3DBBQs excellent instructions as well as others' improvements on his translated narrative).

My only issue is the pressure it takes to release the pvc check valve.  I am using a 3.5" screw through the 90 which is smooth to operate without the check valve pressurized and I have extended it with a small section of pretty rigid irrigation tubing.  The trigger pressure required to release the valve when it is under pressure (20 to 30 psi) seems to be way too much.

Any suggestions on lubing or easing the trigger pressure somehow?

[CaptainSlug]

20 to 30 psi seems awfully high given that you get plenty of performance from this type of setup using as little at 15 psi.

[jamesp]

The only slight modification I did was capped the 1" L prior to connecting to the check and I drilled a 1/16" hole in the cap as was suggested in another write up on the same assembly.  I am guessing that could be the cause of too little pressure to the barrel, but I can't imagine that would be the reason for the increased trigger pressure needed to release the valve.  As a side note, using the trigger mechanism with the backside of the checkvalve disconnected, I can blow in and release the trigger pretty easily.  even when I push the trigger enough to fire, the stefan doesn't go far at all.  like 15 feet.  I'm sure someone is going to ask for photos, so I need to get a photobucket account and take some pics.

[Meaker VI]

I hate to resurrect a 6 month old post, but this is the most recent post that pertains to my issue.

I put together my Mad Ghost (thanks to 3DBBQs excellent instructions as well as others' improvements on his translated narrative).

My only issue is the pressure it takes to release the pvc check valve.  I am using a 3.5" screw through the 90 which is smooth to operate without the check valve pressurized and I have extended it with a small section of pretty rigid irrigation tubing.  The trigger pressure required to release the valve when it is under pressure (20 to 30 psi) seems to be way too much.

Any suggestions on lubing or easing the trigger pressure somehow?

 

Actually, color me curious to the answer as well. I built a Mad Ghost or the free version of the JSPB or something, none of my flow valves (bought several kinds trying to figure it out) would pop when pushed, not easily enough to act as a trigger anyway. I didn't have a gauge on them, but I only filled with enough pressure to seal the valve.

Edited by Meaker VI, 13 November 2017 - 05:40 PM.

[Draconis]

Well, think about it this way:  The force required to open your valve is calculated like this:

Force = (Pressure * Area of valve face) + valve return spring force

 

In the case that it were actually a 1/2" diameter valve with a 1 pound spring (1-2 is common), that would be an absolute minimum of: (0.25")^2 * pi * 20PSI + 1 pound = 4.93 pounds.

 

In reality, most 1/2" check valves have a diameter of about 3/4" to 7/8", depending on the quality, making the range of more like 9-14 pounds on the low end, or 14-20 pounds on the top end.  That's not exactly an easy pull, but you can see how it varies wildly.

Edited by Draconis, 13 November 2017 - 07:24 PM.

[jamesp]

Actually, color me curious to the answer as well. I built a Mad Ghost or the free version of the JSPB or something, none of my flow valves (bought several kinds trying to figure it out) would pop when pushed, not easily enough to act as a trigger anyway. I didn't have a gauge on them, but I only filled with enough pressure to seal the valve.

Thank you for verifying my concern

 

 

Well, think about it this way:  The force required to open your valve is calculated like this:

Force = (Pressure * Area of valve face) + valve return spring force

 

In the case that it were actually a 1/2" diameter valve with a 1 pound spring (1-2 is common), that would be an absolute minimum of: (0.25")^2 * pi * 20PSI + 1 pound = 4.93 pounds.

 

In reality, most 1/2" check valves have a diameter of about 3/4" to 7/8", depending on the quality, making the range of more like 9-14 pounds on the low end, or 14-20 pounds on the top end.  That's not exactly an easy pull, but you can see how it varies wildly.

That definitely makes sense, and although I didn't have the formula for it, in my analytical mind I figured the trigger pressure would be proportional to the chamber pressure as one would need to overcome the other.  So the question really is; is this how this particular trigger setup is intended to function or is there a method to get an easier trigger pull (larger valve, maybe?)

 

Actually, color me curious to the answer as well. I built a Mad Ghost or the free version of the JSPB or something, none of my flow valves (bought several kinds trying to figure it out) would pop when pushed, not easily enough to act as a trigger anyway. I didn't have a gauge on them, but I only filled with enough pressure to seal the valve.

Thank you for verifying my concern

[Meaker VI]

Well, think about it this way:  The force required to open your valve is calculated like this:

I get all that, what is throwing me is that other people have built them using these kinds of valve without trouble. Wait, have you - Youre in my region? If its a regional thing, maybe *all* the valves locally available are too large internally?

[jamesp]

I get all that, what is throwing me is that other people have built them using these kinds of valve without trouble. Wait, have you - Youre in my region? If its a regional thing, maybe *all* the valves locally available are too large internally?

I hate to shoot holes in your theory, but I'm in FL so probably not a regional thing.

[Meaker VI]

I hate to shoot holes in your theory, but I'm in FL so probably not a regional thing.

I was asking Drac, as he *is* in my region, or was last I checked. It might also be multiple regions or a change in manufacturing, I know people have built these things before. I know I tried 2-3 different valves and none worked.

[jamesp]

I was wondering if some sort of lever type system might work to decrease the effort required or magnify the trigger pressure applied.  It seems I'm getting away from the original intent of building a very simple gun.  I just can't figure out how anyone else has made this work easily, not to mention how they have gotten repeated shots out of the tank without re-pumping.

[Draconis]

I get all that, what is throwing me is that other people have built them using these kinds of valve without trouble. Wait, have you - Youre in my region? If its a regional thing, maybe *all* the valves locally available are too large internally?

 

That is a distinct possibility.  The couple of 1/2" units I have handy at work have valves that are well over 5/8" wide, more like 3/4"

 

I was wondering if some sort of lever type system might work to decrease the effort required or magnify the trigger pressure applied.  It seems I'm getting away from the original intent of building a very simple gun.  I just can't figure out how anyone else has made this work easily, not to mention how they have gotten repeated shots out of the tank without re-pumping.

 

Absolutely,  you will just need to devise a mounting method allowing a longer throw on the finger-end of your lever.

[jamesp]

 

Absolutely,  you will just need to devise a mounting method allowing a longer throw on the finger-end of your lever.

...as well as a double lever arm setup as a single (see saw) lever would pull instead of push.  I'm still trying to work that out in my brain.  Flexibility and space availability are pointing me in the direction of a qev.

[jaxmeh]

You could totally use a lever trigger for this. Take a look at Rainbow catch triggers, they're essentially levers that push the catch up. You'd just have to slightly adapt the design to push back instead of up, but it's still very doable.

[Pintotheevil]

...as well as a double lever arm setup as a single (see saw) lever would pull instead of push.  I'm still trying to work that out in my brain.  Flexibility and space availability are pointing me in the direction of a qev.

 

This is probably the reason behind the way 3DBBQ designed the current trigger on the B&B.

 

I've built a few TMG's, and attempted to build a Dyne myself, and I concur getting the trigger right without destroying your finger seems to be the hardest part.  My first trigger used an allen wrench of all things and it worked really well, the only problem is sore fingers(and it wobbled around like crazy;  it was pure jank).  You can think of it like a safety, since you cant pump it more than 3-4 times and still be able to reasonably pull the trigger.  My subsequent triggers used 8/32 threaded rods, a nut, and a faucet seat.  its reasonably comfortable when you don't go past that magic 4 pump number. with that amount of pressure, you get pretty good fps, and anything more just destroys darts anyways.

 

I couldn't get the Dyne I built to work like 3DBBQ's for a similar reason(pumping enough for more than 1 consecutive shot makes it impossible to pull the trigger).  It may be due to the fact that he used what looks like a brass ball valve, and I used a pvc version, and possibly his has more air volume between the ball valve and the second check valve.  I'd have to build a second one to test that out.