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mini hammer valve

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: Ragnarok » Sat Mar 21, 2009 3:07 pm

psycix wrote:The farting machine works!

It's his speciality. If ever you need a pneumatic device to make farting noises, JSR is your man, and you need look no further.

...actually, just get a whoopee cushion instead. :D

</larkingabout>

It's current cycle rate sounds like about 75 Hz, which will obviously need to come back a lot before it's useful. I imagine at the outside, you don't really want more than about a quarter of that.

However, unless I'm mistaken, more pressure will not change the cycle rate (noticeably). Amplitude does not affect resonant frequency.
It's like a tuning fork, which will always make the same note regardless of how hard you bash it - it'll just get louder (in this case, the amplitude represents hammer travel).

Obviously, this is more complex than basic resonance, but I suspect the only methods of changing the frequency noticeably are limited to a heavier hammer, adjusting the overall spring length or adding some form of damping.

Potentially, as the hammer is contained within a conductive brass tube, with a powerful Neodymium magnet for a piston (or as part of the piston), this could be magnetically damped - however, magnetic damping would take careful application, as magnetic damping is pretty strong, and it might be too much for a moderate spring. It could then be that the hammer then didn't hit the valve hard enough - obviously, this would prevent it cycling.

Possibility, but obviously eats energy (as that's what damping is supposed to do!) compared to a heavier piston - and is also somewhat at odds with your "araldite and lollypop sticks" approach. Perhaps better as a theory than practise.
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Unread postAuthor: c11man » Sat Mar 21, 2009 3:24 pm

oh sorry i posted in the wrong topic
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Unread postAuthor: jackssmirkingrevenge » Sat Mar 21, 2009 3:47 pm

Ragnarok wrote:However, unless I'm mistaken, more pressure will not change the cycle rate (noticeably). Amplitude does not affect resonant frequency.
It's like a tuning fork, which will always make the same note regardless of how hard you bash it - it'll just get louder (in this case, the amplitude represents hammer travel).


You're not mistaken, just hooked it up to a 12 gram (couldn't resist :roll: :D ) and got the same angry cycling rate, only more violent due to the increased pressure. I'll try an even heavier bolt but if that doesn't work, it's back to the original micro cloud BBMG idea.
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Unread postAuthor: psycix » Sat Mar 21, 2009 4:53 pm

jackssmirkingrevenge wrote:There's quite a breeze coming out of the exit port at 100 psi, I'm guessing it will be good enough at 400 psi+ I'm also considering a floating o-ring on the bolt as you can feel the air blow past it and it seems a shame to have it wasted.

You will need every puff the shrader puts out as the cycling itself already draws a good amount of power.
Just lube it up to make the o-ring near-frictionless

jackssmirkingrevenge wrote:Balls no bigger than 3mm, I'm not compensating for anything ;)

As long as it are balls of steel, I'll be okay with it.


What made you think that more pressure would cycle it slower, more amplitude?
Heck, with more pressure it could cycle FASTER! Say that it always hits maximum amplitude: the return stroke will always be the same, depending on mass and spring strength, but the first stroke will go faster with an higher pressure!

Of course adding weight should help. It works in theory, so chances are high it will work in practice.
Just add some lead to it.

I dont thing the magnet damping is a good idea. Losing any more energy may stop the cycle.
Unless you use the shrader to pilot something, and put that air out to the hammer.


EDIT, diagram added:
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hammerfarterdiagram.PNG
Hammer strikes on the blue pin, which strikes shrader (or other hammervalve).
The rest should be self-explanatory.


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hammerfarterdiagram.PNG (4.09 KiB) Viewed 744 times
Last edited by psycix on Sat Mar 21, 2009 5:14 pm, edited 1 time in total.
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Unread postAuthor: Ragnarok » Sat Mar 21, 2009 5:09 pm

jackssmirkingrevenge wrote:You're not mistaken

Woo!

*Marks point up on scoreboard of awesomeness*

psycix wrote:I dont thing the magnet damping is a good idea. Losing any more energy may stop the cycle.

I said that by my own admission.

I was just listing ways to alter resonant frequency, of which damping is one and I wanted to give an example of how it could be done, so it fitted with the more solid "heavier hammer" and "longer overall spring length" suggestions.
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Unread postAuthor: THUNDERLORD » Sat Mar 21, 2009 8:55 pm

Looks like a major breakthrough!!! :)

I was wondering if you tryed turning the co2 tire filler upside down(?),
Seems like the co2 liquid would hold the spring back longer as it turns from liquid to gas (resulting in more volume gas).

... Maybe a springless design with a shrader at each end only one regulated to lower pressure The pressure piped behind the hammer wouldn't be too much of waste because if it leaked it would leak to the front. ( I've been wondering about car air-shock design and spec.s lately)

Ragnaroks magnet caused me to remember an electric induction or generator connected (like a simple shake up flashlight),
But then it would need fiddly some electronic to use the power generated.
(I've been daydreaming about a filling the chamber concept lately,
Something like having another smaller chamber behind a piston in the chamber, then the compressed air behind the plunger inside the chamber could be shot from a second smaller barrel, or even act as a small volume compressor, refilling the chamber some maybe(?)...Or a captive bolt could pulse out the front of the firing chamber too :twisted:
Interesting because no pressure would be wasted since it's already available... But just a daydream for now.

I've been thinking of using springs from tire gauges (cheap, stick spring plunger type) seems like the distance would be the same as the reading on the gauge with the same pressure applied. Edit:with the same diameter plunger.
That's about 100-120 PSI fully compressed,
so if four were used it would take around 400psi to compress, and so on.
I am wondering if they can be used lengthwise (series) Rather than width wise(?)

Awesome air motor and hammer valve design you've built so far.
Also JSR + design without epoxy = bound to be interesting!!! :)

I don't see so much problem with faster rate, prehaps it could be connected to one of your blow-forward bolts (metal one of course).
The magazine might need to work like a cloud chamber at that rate though!!! :roll: :wink:

BTW, I'm considering changing my "Tire" to "Tyre" to show respect! :P 8)
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Unread postAuthor: Lentamentalisk » Sun Mar 22, 2009 1:55 am

adding in series halves the spring constant, while adding in parallel doubles the spring constant.

Liquid CO2 will just kill the effeciency, because of the freezing problems you will get.
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Unread postAuthor: inonickname » Sun Mar 22, 2009 2:27 am

Be careful, with liquid CO2 it will easily outcool the friction heating and end up making the gun jam/freeze..
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Unread postAuthor: THUNDERLORD » Sun Mar 22, 2009 3:07 am

Be careful, with liquid CO2 it will easily outcool the friction heating and end up making the gun jam/freeze..


Well that would accomplish a lower rate of fire!!
Hammer freezes in place, warms back, unfreezes and smacks the shrader again :lol:

@Lentamentalisk, Thanks for the spring info.
The problem with parallel springs is getting the plunger diameter the same as the original gauge.
Guess the spring tension still needs trial and error method.
Wondering though with half the spring constant (series) it would be half but twice the distance travel or...(?)
Thanks.

BTW I've found 5/8 inch thin brass tubing from hobby shops fit so snugly in a 1/2 inch brass 6" pipe nipple, that it has to be lined up just right...And the brass on both is shiny smooth.
It would be good for a piston or steam engine cylinder etc. components.
Been thinking on unregged co2 designs since I found dry-ice nearby. 8)
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Unread postAuthor: inonickname » Sun Mar 22, 2009 4:24 am

In most hobby stores you can get telescopic brass tubing- i.e. the tubing I.D. is a tiny bit larger than the last sizes O.D.

They're manufactured with very tight tolerances.. As far as I know JSR uses them in many designs, including the 6mm semi etc.

I'll also be using them in my next blowback design, but due to the thin wall they are probably unrifleable.. May have to also incorporate a commerical barrel.

You could lay a smaller diameter spring inside a larger spring..
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Unread postAuthor: psycix » Sun Mar 22, 2009 6:37 am

Modified the diagram, this time with a lever to make sure there's way less dead space.
The lever could also be used as a transmission, being able to use a mechanical advantage.
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 22, 2009 1:45 pm

Even with a heavier bolt, it still cycles like mad. The power probably wouldn't be as good as a pop-off valve setup, I don't think this one will get developed further.

Interesting working with hammer valves though, maybe I could scale it up and combine it with a blow-forward bolt roughly like so:

Image
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Unread postAuthor: psycix » Sun Mar 22, 2009 6:36 pm

JSR wrote:Even with a heavier bolt, it still cycles like mad.

Add MAD weight then!

1 hammer mass -> 75 Hz
75 hammer mass -> 1 Hz
Of course it wont work like that, but you get the idea. Your hammer may need to become 10 times as heavy (or even more).
Heck, why dont you try holding the HAMMER and let the gun move back and forth :roll:

JSR wrote:Interesting working with hammer valves though, maybe I could scale it up and combine it with a blow-forward bolt roughly like so:

It may indeed be a good idea to use that system along with the hammervalve+pistonvalve to make sure you'll get a large enough puff of air each cycle.
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Unread postAuthor: Ragnarok » Sun Mar 22, 2009 7:06 pm

psycix wrote:Of course it wont work like that, but you get the idea. Your hammer may need to become 10 times as heavy (or even more).

Resonant frequency in a solely spring based system is:
Frequency = SQRT(k/m)/(2*pi)

That is to say, the frequency is related to the square root of the system mass. Assuming this to follow the same rules, to bring it back to 10 Hz, he'd need a hammer about 50 times heavier.

Alternately, he could use a spring that had 2% of the spring constant k - or any combination of the two.

Last option, very strong spring, very large mass, and damping - but like I said, too much damping and it might fail to cycle at all.
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Unread postAuthor: JDP12 » Sun Mar 22, 2009 7:43 pm

hmm very interesting... I like the idea! Can't wait to see progress
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