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New advances in hand pumps

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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New advances in hand pumps

Unread postAuthor: Lentamentalisk » Sat Mar 01, 2008 4:43 pm

I just had a brilliant idea for a pump.
Everyone is always complaining about the time it takes them to pump up their tanks if they want to get it to a high pressure, because their high pressure pumps have such a low flow. I present to you the solution to this problem, the two stroke pump:
Image
With this pump you screw the small diameter portion into the middle section, and have a high flow low pressure pump. When it gets too tough to pump you screw the middle into the bottom, and unscrew the top from the middle. Ta-Da! You have a low flow high pressure pump!

This idea can theoretically be extended many times, so you could make an even smaller pump inside the top section, or a even bigger tube around the bottom, its very flexible.

The other feature is that instead of getting its air from the environment, it gets it from the port on the left, meaning that you can pump from your hydrolysis machine or a premixed set of gases, or what ever you want.

What do you all think?
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Unread postAuthor: brother361 » Sat Mar 01, 2008 4:51 pm

wow it seems like it would work mnow u should go and make it
but the idea i think is preety good
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Unread postAuthor: Ragnarok » Sat Mar 01, 2008 5:25 pm

Although it's a good idea, it's not entirely new. The Joe Blow Ace pump works on a similar principle, except it uses two individual pump tubes for the job (so you can use both together, the large one, or just the small diameter one for three different options.)

Now I think, I even remember helping with a design practically identical to this, if designed for water, well over 2 years ago.

It's a more than workable idea, but I think that two strokes is a practical upper limit, after that I can see problems arising.

However, it might just be simpler to have a conventional bike pump for getting to 150 psi reasonably fast, then swap to a homemade high pressure one - which was an early plan I had to help my pressurization, but it later got overshadowed by other ideas.

Go for it if you want, but I think it over complicates things, adds more seals that could leak, among a few other problems. Done well, it could be very useful, but it would need careful construction.
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Unread postAuthor: potatoflinger » Sat Mar 01, 2008 5:31 pm

I think it sounds like a great idea, you should definitely attempt to make one.
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Unread postAuthor: Hawkeye » Sat Mar 01, 2008 5:51 pm

I have a schrader on a larger chamber gun and also a fill valve that my homemade pump threads onto. I can then pump it quickly to 200 or so with a bike pump and then top it up with high pressure homemade model.
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Unread postAuthor: Lentamentalisk » Sat Mar 01, 2008 5:58 pm

the idea is best fit for mounting on a gun that you dont want to have 2 pumps strapped to. I realize that compressors are much faster, but they are heavy and require a battery/outlet to work. This is a fast way to fill up your chamber with a gun mounted pump.
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Unread postAuthor: Hawkeye » Sat Mar 01, 2008 6:09 pm

It still has to be attached in a way that allows ease of pumping. No sense having one that you can't really apply pressure without possibly snapping something.
Mine is attached so that I use the brass T on the pilot area as a handle while the traditional handle goes against the ground. Upside down like the Girandoni pump.
Another option might be one of those swivel air fittings. You could lie the gun on the ground and swivel the pump upright. A swivel air fitting is about 12 dollars in the compressed air tool section.
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Unread postAuthor: Gippeto » Sat Mar 01, 2008 6:29 pm

Sorry, I can see this working quite well with water, but not with air.

If I'm missing something please let me know.

As soon as you achieve some amount of pressure, the outer pump cylinder will stall in the extended position. Leaving the small cylinder to do the work. Then your compression ratio goes out the window. Mechanical compression ratio is essential for getting high pressures with air.
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Unread postAuthor: Lentamentalisk » Sat Mar 01, 2008 6:41 pm

you pump with the big one until it starts getting too hard... you dont wait till it is completely impossible to pump the big one... That is why there are screw fittings. You screw the big one down so that you only use the small one... So long as you arnt a robot, you will be able to tell when the big one starts getting hard to pump.
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Unread postAuthor: Hawkeye » Sat Mar 01, 2008 7:15 pm

You will need a one way valve in the larger pump head so that the smaller pump can fill the gun chamber.
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Unread postAuthor: ghostman01 » Sat Mar 01, 2008 7:26 pm

yeh wont the smaller pump push the larger one down when you use it ??
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Unread postAuthor: Lentamentalisk » Sat Mar 01, 2008 7:43 pm

neither of you get the point at all. The smaller one is screwed into the larger one when you are using the larger one, and the larger one is screwed into the base when you use the little one. No you dont need a check valve in the larger ones head, because that would make it not work at all. As you may have seen from the diagram, those O-rings are fixed in place, and there is no air that leaks past them. The entire point is that it pulls from one port, and pushes air out of the other...
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Unread postAuthor: bluerussetboy » Sat Mar 01, 2008 8:00 pm

nothing revolutionary, you see this design on pumps for rafts and inflatable kayaks and air mattresses. i don't see this working well for the high pressures needed for spudgunnery.

i don't think your lower inlet/exhaust fitting will be efficient. too much dead space for your 'high' pressure to be productive. and dead space kills high pressure pumps.

what is your pipe diameters going to be? 1" > 3/4" > 1/2"? making larger jumps in diameters can be tricky if they don't make the right fitting. if you have to start using combinations of fittings this pump is going to get expensive real quick. if your going to make custom fittings then expect to pay more money.

JSR has been doing a lot of talk lately about small chamber/high pressure being more efficient. i think he's onto something. this pump design isn't it.
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Unread postAuthor: Lentamentalisk » Sat Mar 01, 2008 8:16 pm

1"? do you realize how little pressure you can get out of that?
I was aiming for 1/2" and 1/4". At 1/2", you get a 1:5 force to PSI ratio, and 1/4" you get a 1:20 ratio... I don't see why it wont work for high pressures.

As for the dead space, that is what epoxy puddy is for. I realize that dead space is bad, but as everyone knows, its also easily fixed by putting something in that space. Problem solved.

Are there any throughly thought through comments that anyone has?
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Unread postAuthor: Hawkeye » Sat Mar 01, 2008 8:19 pm

Yes I do get it, I just forgot that the small pump head locked in the bottom position basically has the two o-ring seals functioning together as the larger pump seal.
I think dead space will be detrimental. The only reason to make a pump of smaller diameter than 3/4 is to go over 400psi. Do you need that?
A happy medium is a chamber that goes to 350 with ten strokes of a 3/4 bore pump.
I think two separate pumps is a simpler solution if you need 500 plus psi.
A half inch top up pump that is about twice as long as a shock pump and lets you use your body weight to pump it is a pretty compact piece.
My next project is a (JSR inspired) pistol that operates at 500 psi and it will use a small pump of that size.
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