Pressurised plunger system - false physics?

Hey guys, just wondering if someone could help confirm/deny a concept I've been playing with. I'm no physics major so I don't know quite where to begin with formulas and equations.

The idea is to have a plunger system, hooked up to a solenoid valve as opposed to a traditional trigger/catch system. The plunger would have to have a 100% seal (or close enough to that) in order for it to work. Once the plunger is primed, the air inside the plunger tube would (theoretically) be compressed against the solenoid valve - maintaining the primed state until the solenoid is activated and the air is released.

My questions are:

A) Would it in fact be compressed air as opposed to unabated air flow found in stock Nerf guns?
B) Would it be more effective than aforementioned stock Nerf air flow? i.e. would the compression gained be more effective than straight air flow?

The idea would be to make something to bridge the gap between air pump Nerf guns, and spring powered Nerf guns, giving you the ability to use compressed power but with minimal input by way of priming.

Hope this makes sense, if a diagram is needed please let me know and I'll sketch it up.

Thanks in advance!

(Please let me know if I'm breaking forum etiquette, I'm not exactly a regular poster)

- stoph

Hey, I like that idea!

No idea if that would work, but it sounds like it would.

If you could chuck up a sketch I recon we could get a clearer idea of what your idea is.
I am kind of intreagued

Thanks! I remember seeing a modded NF on Nerffornothing that used an air pump to prime the spring, and the trigger system was a simple valve, which got me thinking it could be possible. I don't want a gun that kills, but for a relatively low input I figure that decent performances could be achieved, perhaps by using a large diameter, short stroke plunger (with air holes in the back end to allow for a rapid discharge).

I don't have my graphics tablet on me right at this moment, but let me try and draw something up real quick.

Not sure what you mean about compressed air vs unabated air flow? My understanding is the spring compresses the air until the dart begins to move and then it pushes the air out of the barrel

If you are thinking about replacing the spring with a solenoid there are two things to work out. How much electricity will be required to pull the solenoid and does the solenoid move as fast as a spring?

If you could get it to work the advantage would be that the plunger would prime itself once the power was cut to the solenoid. Solenoids usually have a spring that returns the plunger to the rest position. of course this spring would need to be strong enough to slide the o-ring inside the plunger tube and then the downside is that when you power the solenoid the return spring then is working against itself

My suspiscion is that a solenoid with the amount of travel and power needed wil require a lot of power to activate

Interesting idea though

Monitoring this thread.

Are you talking about using compressed air to inflate a springer style plunger, or using a springer style plunger to draw air into the plunger tube *and* compress it?

If the former, it's been done in several systems, the one that comes to mind is the Super Soaker ShotBlast. Works very nicely since you've got compressed air but no deadspace once the tank is emptied.

If the latter, I'm not too sure how well it'll work, because you'll no longer have the velocity of the plunger working in your favour, and relatively little air to work with compared to the former.

@238232: I'm thinking more along the lines of the former - hopefully this diagram explains it a little more clearly.



The plunger is primed once with a priming handle, compressing the spring fully. Because there is no catch, the spring would want to release the air straight away, were it not for the seal created by the solenoid valve.

If my thinking is correct, the air would be compressed against the solenoid valve (shown in red), thus providing more compression than is found in a stock Nerf gun. You wouldn't be using the rear of the dart to create the seal.

Thoughts? Is it a dud idea? Am I missing something?

I'm still wondering what you mean when you say "primed once", it makes me think you're just pulling the plunger rod back to get air into the tube. Is that the case, or are you thinking of using a regular air pump to fill it?

The Water Warrior, "Pulsator" series and Nerfs, ShotBlast/QuickBlast (as mentioned by 238232) already use this concept. Jerm, on Youtube, has modified a NF using a Pulsator tank. It's pretty powerful.

To answer your original question, yes, this would work... and work extremely well.

BuffDaddy has already created a proof of concept. A link to his work can be found here: http://nerfhaven.com/forums/index.php?showtopic=21513

stoph wrote:@238232: I'm thinking more along the lines of the former - hopefully this diagram explains it a little more clearly.



The plunger is primed once with a priming handle, compressing the spring fully. Because there is no catch, the spring would want to release the air straight away, were it not for the seal created by the solenoid valve.

If my thinking is correct, the air would be compressed against the solenoid valve (shown in red), thus providing more compression than is found in a stock Nerf gun. You wouldn't be using the rear of the dart to create the seal.

Thoughts? Is it a dud idea? Am I missing something?

I tracked down the post on the NF pump gun on Nerffornothing that triggered my concept, the link is herehttp://nerfornothing.blogspot.com/2011/05/custom-nerf-pulse-master-pistol.html. It uses an AT3000 pump and a water gun tank to do what it does, and the video shows quite simply how it operates. Where my concept differs is that I'm not pressurising the air that's in the plunger any more than what a single priming offers, but I'd still be getting full compression from the spring.

@238232: Sorry, missed your question from earlier and you beat me before I could edit and reply. The premise of the concept is that you would only prime once and not require pumping. Essentially, you are only cocking the gun. This is where my main concern lies: whether there would be any difference between a regular catch/trigger sytem vs the solenoid system I'm proposing.

@makeitgo: Ah, you're on the same page - excellent! Thanks for providing extra links for me to check out.

The bit I'm concerned about is a "single priming". By that you mean only one pump right?

If so, then you'll need to have one of the following:

a) A very large pump or a very small tank. The compression of the spring will be limited by the amount of air you can cram into the tank, which will determine the pressure inside the tank and thus the force acting on the spring to compress it.
b) A very weak spring. The converse of the above, if you can't build up enough pressure from a single pump, then weaken the spring. Eventually this will be self-defeating as the spring strength approaches zero.

It could work, but it sounds to me like you're going to have to satisfy one of those conditions. You'll notice that Buffdaddy's homemade pulsestrike that MIG linked to, he pumped multiple times before he fired.

If i'm understanding correctly, this allows for airgun power with a single stroke?

Put a one-way valve in the plunger head and you're done. Pull back like a xbow, chamber a terrifying shotgun load with 50% of darts facing backwards for spread, release and let the spring compress the air, pull trigger which actuates solenoid valve.

mister_elliott wrote:If i'm understanding correctly, this allows for airgun power with a single stroke?

Put a one-way valve in the plunger head and you're done. Pull back like a xbow, chamber a terrifying shotgun load with 50% of darts facing backwards for spread, release and let the spring compress the air, pull trigger which actuates solenoid valve.

Thats exactly what I'm going for. I don't want a gun that will kill, if I wanted something like that I'd use a tried and tested airgun system. I want something that would be usable at wars, as you could theoretically dial in a reasonable range/power depending on how much you compress the spring.

Sorry for all the posts. I figured I should clarify a little more. There would be no pump in this setup - the only force exacting on the spring would be a traditional springer grip being pulled back once. Does this help? Sorry I'm still trying to get my head around the physics of it..

238232 wrote:The bit I'm concerned about is a "single priming". By that you mean only one pump right?

If so, then you'll need to have one of the following:

a) A very large pump or a very small tank. The compression of the spring will be limited by the amount of air you can cram into the tank, which will determine the pressure inside the tank and thus the force acting on the spring to compress it.
b) A very weak spring. The converse of the above, if you can't build up enough pressure from a single pump, then weaken the spring. Eventually this will be self-defeating as the spring strength approaches zero.

It could work, but it sounds to me like you're going to have to satisfy one of those conditions. You'll notice that Buffdaddy's homemade pulsestrike that MIG linked to, he pumped multiple times before he fired.

stoph wrote:@238232: Sorry, missed your question from earlier and you beat me before I could edit and reply. The premise of the concept is that you would only prime once and not require pumping. Essentially, you are only cocking the gun. This is where my main concern lies: whether there would be any difference between a regular catch/trigger sytem vs the solenoid system I'm proposing.

Right, I get you now.

This is what I'd say will happen:


1) You pull the plunger rod back. Total amount of air will be one plunger's volume at atmospheric pressure.
2) You let go of the plunger rod (solenoid valve is still closed). It goes forward a fair bit (note wasted energy here) and compresses the air.
3) You open the solenoid valve and the dart goes on its merry way.

The main thing that doesn't look good to me about this system is that you're essentially wasting energy by using the spring to compress the air instead of doing it yourself (2 step process as opposed to a 1 step process). Summing the energy, while you might get springer ranges, you will probably get less, and you certainly can't get more energy out than what you put in while priming it.

Still, do it and see what happens. I'd like to be proven wrong on this, but it just sounds to me like it's a more complex system (adding the solenoid valve) for little/no gain.

Interesting thread...

Stoph, could you start using the edit button mate. You've got multiple double-posts in this thread, which would generally put a couple of strike's against you. I realise you're new to the forum, so if you could utilise the edit button from now on, it would be greatly appreciated.

Also, could you please update your profile with an avatar, age, location etc etc

Keep up the good work with original concepts.

Cheers,

@238232: Ah you are totally right! It makes sense now, I just needed a sounding board to bounce it off cause it's been rattling around in my head for a while and I haven't been able to make head nor tails of whether it would work. Looks like it's back to the drawing board, but thank you very much for your patience and help on the matter!

@clunk07: Very sorry about that mate, I will do my best in future to keep track of my posts. I've updated my profile as per your request. Thanks for being understanding and patient as well, I appreciate it.

Thanks guys! I'll try and work out an alternative.

- stoph

No problems at all mate, I think we all can get carried away at times, and lose track of posts. Especially when brain-storming.

Stick with it, I'm sure you'll come up with something more plausible.

Cheers,

Now that I understand what your going for (a single prime), 238232 is absolutely right. In terns of physics, energy would be wasted. Potential energy from the spring compresses the air but 'heat' is also created during this process. Since the spring is 'stopped' before release, it also loses momentum. The heat created by compressing the air and stopping the plunger head, is what gets wasted. It may not seem like a lot but it's enough to affect the ranges you are hoping to achieve.

@238232 you will not be proven wrong.

I guess it depends on what you are trying to achieve...

I see this as a cool way to reset/cock the spring loaded plunger and achieve a semi auto effect.

It would be spendy $$, but could be done with a small compresser or a small compressed air cylinder (there are some excellent rescue breathing apparatus options in carbon fiber), with a 2 way solenoid controlled by a switch on the trigger.

I just don't see it utilizing the spring power and compressed air together...

Either the air pressure would be high, and have expelled the dart before the spring fully released,

OR

The air pressure will have leaked down (more likely) and you'd just be getting the spring power.

It would take one very tight (and high friction) plunger seal to hold the air pressure.

I would probably prefer to be pumping up an air blaster tank, and using the solenoid setup for a high powered semi auto that way.

But it looks like a great idea worthy of further investigation

But after reading more carefully, you aren't introducing compressed air??

Then no, the air tight seal would be too tight to release properly IMO.

But I could be wrong, only trying will tell for sure...

pretty something similar exists (shot blast tank)
but it doesn't work exactly like this.