Need help: can we make a suction device out of a water gun?

General water gun discussion.
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ewright
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Need help: can we make a suction device out of a water gun?

Post by ewright » Tue Sep 29, 2009 10:14 am

Hey everyone,

I was hoping that you could help me on a small problem I am trying to solve. I am a doctor working in southeastern Uganda and the regional hospital here doesn't have any good machines available for medical suction. We cant use anything that requires electricity because the power is intermittent, so I got to thinking about the super soakers that I played with and how they seem like relatively inexpensive and readily available air pressurization devices. The question I have is: can I buy a water gun off the shelf and then make some quick and simple modifications to make it into a vacuum generating device rather than a pressure generating device. I was hoping that it might be as straightforward as reworking how the valves are connected, but since you guys are the experts at this sort of thing I figured I would seek your advice and guidance first. Any help you can offer would be appreciated. Thanks!

ernie :)

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isoaker_com
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Re: Need help: can we make a suction device out of a water gun?

Post by isoaker_com » Tue Sep 29, 2009 1:39 pm

For many water blasters, you wouldn't need to really make any modification to the water blaster, itself. Rather, you'd need to hook up tubing securely to the reservoir and/or reservoir intake. The main problem I foresee is that I'm not sure how much vacuum power you're hoping for. Not sure how much negative pressure you can generate with a typical blaster's pump. As well, the seals on typical stock water blasters aren't really designed for prolonged exposure to negative pressures... might work at first, but once the seals give up, repairs may not be simple.

You may be better off making a simple, but more durable homemade pump.

:cool:
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Silence
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Re: Need help: can we make a suction device out of a water gun?

Post by Silence » Tue Sep 29, 2009 7:36 pm

Same questions here: how much negative pressure? And are you sure you can't find hand-powered vacuum pumps anywhere? And do you already know how you're going to keep fluids from rushing into the device?

If you build a pump you may want to use a syringe for the seal, as homemade pumps can leak a bit and aren't always reliable. The biggest problem is that you can't maintain a vacuum continuously with piston pumps. A large tank may let that suction last longer, although you'll still have to empty it of air again afterwards.

ewright
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Re: Need help: can we make a suction device out of a water gun?

Post by ewright » Wed Sep 30, 2009 5:49 pm

Hey guys: first thank you for your replies and helping me to think a little more about exactly what I am trying to accomplish. I think the key is that I am trying to find a suction device that I can buy off the shelf and modify minimally in order to produce a vacuum for as long of a time as possible without needing to be "re-pumped" to reestablish the vacuum. I was thinking that a water blaster would be a good candidate because:

1. they are relatively inexpensive
2. they are readily available
3. the trigger mechanism would allow us to turn the suction on and off easily
4. the large chambers could produce a suction force that wouldnt need recharging often

In reply to some of your questions: we wouldnt be looking for much suction force to be generated (essentially enough to just suck fluids out of a patients airway) and we would keep fluids from rushing into the chamber by installing a catch basin in between the device and the patient to capture all the fluids being sucked out. So I guess the essential question is:

Is there a way to modify a water blaster to generate a vacuum that doesnt need to be recharged often, and then to use the trigger to switch the suction on/off.

Thank you again for all of your replies, Im looking forward to hearing your ideas.

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cantab
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Re: Need help: can we make a suction device out of a water gun?

Post by cantab » Wed Sep 30, 2009 6:22 pm

ewright wrote:Is there a way to modify a water blaster to generate a vacuum that doesnt need to be recharged often, and then to use the trigger to switch the suction on/off.
No. A partial vacuum would readily be created by reversing the one-way valves - though since water blaster's pumps and valves are designed for water, not air, you may encounter trouble. But when you open the trigger, air will rush in and you'll lose your vacuum. Even the largest of chambers would fill in seconds.

To be honest, I think you're going to need a motorised pump. If you can rely on electricity at least sometimes, charge a car battery when the electricity's on, and run the pump off the battery. Or even run it off a battery in a vehicle.

PS: Is what you seek the device sometimes known as an aspirator?
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
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Silence
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Re: Need help: can we make a suction device out of a water gun?

Post by Silence » Thu Oct 01, 2009 12:06 pm

You're going to have problems if you expect to not need pump often. Can you calculate the volume of vacuum that you'd need to use in, say, an hour?

Producing the vacuum itself would indeed be easy - just know that sucion would appear at the inlet, closer to the water reservoir. The fact that you're pumping airwill make a difference if there's a lot of "dead space" between the valves and the pump, because air is compressible. Some of the air will just expand out of and contract into the dead space as you pump. I'm not saying this will be a problem, just that most water guns were not designed with this in mind.

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SSCBen
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Re: Need help: can we make a suction device out of a water gun?

Post by SSCBen » Sat Oct 03, 2009 3:54 am

Welcome to SSC!

cantab mentioned what's called an aspirator which may be what you're looking for: http://en.wikipedia.org/wiki/Aspirator

This device can generate a vacuum from a flow of a fluid. The fluid flows from an inlet through an outlet and it sucks in the fluid on a second inlet. You basically need only a tee, some tubing, and a way to attach it to the nozzle of the water gun. As I have no experience with these devices I can not speculate on its efficacy with a water gun as the power source.

Edit: It's not as simple as I indicated here. A low pressure region must be created by accelerating the water through a nozzle or orifice. Consequently a simple tee as described above is not adequate by itself. A modified tee would work.

The simplest solution is a large syringe-like water gun with a tube attached to the nozzle.
Last edited by SSCBen on Sat Oct 03, 2009 1:26 pm, edited 1 time in total.

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cantab
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Re: Need help: can we make a suction device out of a water gun?

Post by cantab » Sat Oct 03, 2009 12:50 pm

The medical aspirator is something different, I'm not sure if they use the same principle.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

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SSCBen
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Re: Need help: can we make a suction device out of a water gun?

Post by SSCBen » Sat Oct 03, 2009 1:23 pm

I see. The photo on the Wikipedia page about the medical device seems to be a reasonably simple way to accomplish this: http://en.wikipedia.org/wiki/Aspirator_ ... evice[/url)

By reversing the pump in a water gun a similar effect probably could be achieved, but I'm unsure of how well a water gun will work when pumping a vacuum or if the PCs in a modern water gun would collapse under vacuum pressure.

Reading the page about the other aspirator I mentioned, it says at 25 C (77 F) it can generate a vacuum pressure of 3.2 kPa (0.46 psi). That's not bad. With a large enough pressure chamber you could have potentially minutes of continuous suction too.

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martianshark
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Re: Need help: can we make a suction device out of a water gun?

Post by martianshark » Wed Oct 07, 2009 4:28 am

Would it work if you simply turned the check valves around?

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cantab
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Re: Need help: can we make a suction device out of a water gun?

Post by cantab » Wed Oct 07, 2009 9:15 am

For a brief period. The problem is the pressure chamber's not big enough. Air moves faster than water. Take any water gun you have, air pump it a lot, and fire - the air shot time will be much less than the usual water shot time.

Also, as I alluded to before, that may not be so simple. You're gonna have to cut and rejoin pipes that aren't meant to be cut and rejoined.
I work on Windows. My toolbox is Linux.
Arsenal:
Super Soaker: XP215, 2xXP220, Liquidator, Aquashock Secret Strike M(odded), Arctic Blast M, CPS1200, CPS2100, SC Power Pak, 3l aquapack, 1.5l aquapack
Water Warriors: Jet, Sting Ray M, Shark, Argon M, Tiger Shark, PulseMaster
Others: Waterbolt, The Blaster, Storm 500, Shield Blaster 2000, generic PR gun, generic backpack piston pumper (broken), 3l garden sprayer M, 10l water carrier:

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martianshark
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Re: Need help: can we make a suction device out of a water gun?

Post by martianshark » Thu Oct 08, 2009 11:24 pm

Wait-We're working with air? I thought we were working with liquid, that way when you turn the check valves around, the liquid goes into the reservoir. In that case, couldn't we turn the check valves around and give it a PC expantion?

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