Dual-Stage Pump

Build a homemade water gun or water balloon launcher and tell us about it.
User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Dual-Stage Pump

Post by Silence » Wed Apr 26, 2006 12:52 am

Okay, here's another homemade pump idea: wouldn't it be pleasant to have a pump that had both large and small pistons? This would allow fast pumping at the beginning (when the pressure is low), but as the PC fills and the pressure increases, you can use a narrower pump piston to make pumping easier.
Image
Basically, there are two stages: when the pump is 100% to 50% extended, more water is pump because both the wider and the narrower pistons are moving; but when the pump is 50% to 0% extended, only the narrower piston is moving, so pumping is easier. This setup is also somewhat balanced because one should be able to exert more force in the first stage and less in the second, though my logic may be faulty.

Usage: at the beginning, pump only in the first stage; then, use a combination of the first and second stages; and finally, when the pressure is almost at its maximum, only use the second stage. This makes your pumping the most effective.

All, right I admit this is a radical idea and would be too complex and expensive to actually implement. However, I am looking for suggestions on how to change it and make it more practical. If it can be done, it will be done!

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Wed Apr 26, 2006 8:42 pm

Perhaps you should consider two pumps?

A small and a large one - much simpler to build and less likely to go wrong.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Wed Apr 26, 2006 8:51 pm

Yes, but that would be bulky.

I thought of a problem: the inner piston piece (freemoving) can't be pushed back all the way (or can it)?

User avatar
m15399
Posts: 224
Joined: Sat Oct 15, 2005 1:54 am

Post by m15399 » Thu Apr 27, 2006 4:04 am

All, right I admit this is a radical idea and would be too complex and expensive to actually implement.
What makes you say that? It shouldn't be too complicated. Use some 1" pipe and some 1/2" pipe with a reducer in the middle, and then the pump shaft shouldn't be too hard either...

What do you mean "pushed back all the way"? Do you mean to the right or to the left on your drawing. If you mean that it won't be able to re-enter the pipe, I'm sure it will. If you use a reducer, it will be a cone shaped thingy inside so the piston will be perfectly guided.

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Thu Apr 27, 2006 8:18 am

I think that two pumps could actually be more compact and practical than something like this.

I still don't know exactly how this design is supposed to work - I'm good at missing things like that.

If you think that it can be done, then try it and tell us how it went. You could be hailed as the inventor of the dual-stage pump, the creation that almost no homemade goes without.

EDIT: I think I've worked out how it works now.... it seems like a very novel idea - I think I might try it sometime if I find the resources...
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Thu Apr 27, 2006 2:06 pm

@ m15399: By "pushed back all the way," I meant completely extended; that would be all the way to the left.

Okay, I found the possible problem that was bugging me earlier. See the pip on the pump rod that is the farthest to the left? Well, the opening where the rod enters has to be large enough to allow that pip to freely move in and out.

And there's an even bigger problem: first of all, you're going to get maximum resistance when the pump is in the second stage; second, you won't be pushing anything in the first stage; and third, in the second stage, the larger piston can't push water anywhere because the smaller piston will be blocking the path.

Wow, I don't know what I had been thinking. I'm pretty sure the design that had been in my head was different from the one that I posted. I'm sure there's a way to get what I want, but it will need a new design--from the ground up.

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Thu Apr 27, 2006 7:40 pm

You'd need at least three check valves to make that one work. I'll come back with an animation to show how I think it could work.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Thu Apr 27, 2006 9:33 pm

I don't know what your intial plans where, but this is how I see the design working (I assume this isn't quite how you saw it working because I didn't encounter any problems...)

Single stage use:

Image

Use of both stages:

Image

I really like this design, and I might even use it on my APH (which might become a PCgH, but I'm not sure.)

Seals shouldn't be a problem, and cost shouldn't be a major barrier to implementing this.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Fri Apr 28, 2006 7:02 pm

On further news on this topic, I went to the trouble of setting up a spread sheet to calculate pumping efficency. I've used two forms of efficency:

Pumps to pressure: Simple enough - the amount of pressure after a certain number of pumps.

Pump distance to pressure: More complex. The pressure after a certain distance that the pump shaft has travelled. Only the pressurizing stroke is counted.

These figures are based on the following data:
2000 ml PC (yes, quite large)
Total pump length 30 cm - equally split between stages
Person capable of exerting 20 lbs of force on the pump.
No precharge on the chambers

Pump 1: (blue) One stage - 1/2" ID
Pump 2: (pink)Two stages - 3/4" and 1/2" IDs
Pump 3: (green) This is just for interest: Three stages - 3/4", 1/2" and 3/8" IDs
Pump 4: (red) Two stages - 1/2" and 3/8" IDs

The following graphs result:

Image

Image


Ignore the fact that the pink and blue/green and red lines end at different pressures - they will be able to achieve the same eventual pressure.

The dots show the end of each pump stroke - thus the space between dots shows the effect of that pump on the pressure.

The steeper the gradient of the curve, the harder it will prove to pump.

As you can see the higher bore two stage pump is very effective - it will raise pressure faster than either of the other two pumps, and can achieve a decent pressure.

The green line (three stage) reaches over 150 psi - the 3/8" ID for the last stage really boosts the pressure. In terms of distance pumped, it is more effective speed wise than the standard pump, and can reach much higher pressures.

The red line reaches over 150 psi, but is slowest to pressurize overall. The low capacity limits it's pressurization speeds.

Note: There was a problem with the graphs, but it has now been corrected.
Last edited by joannaardway on Fri Apr 28, 2006 9:12 pm, edited 1 time in total.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
SSCBen
Posts: 6449
Joined: Sat Mar 22, 2003 1:00 pm

Post by SSCBen » Sat Apr 29, 2006 8:49 pm

Interesting ideas. I believe that there was some similar discussion last year with a different and more compact design. If I remember correctly, DA (ZOCCOZ, etc.) suggested a two-stage pump where an outer and inner pump exists. Essentially, this system will be compact, allow for two internal diameter, and not change the design substantially (a single check valve can be used).

The larger pump will be used until pumping becomes hard, where the second internal pump will be removed and used. The system does seem to have a few issues to work out (such as if the smaller pump should lock in place).

Here's my poor drawing (feel free to remake it):

Image

On second thought, please do remake that image. The best way to describe the system is via an image.

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Sun Apr 30, 2006 5:42 pm

Wow, I'm gone for just a few days, and so much more content is posted that I don't have time for it! Nice job, joannaardway.

Yes, I told you there was a problem with my design. I had something else in my mind, and although you managed to fix this one, a new method built from the ground up might be better. In addition, you don't need such a long plunger for the wider piston tube, unless you're worried about tilting problems.

It's good to know that somebody else appreciates PCgHs--like CPHs, they are vastly under-represented.

You did an excellent job with the graphs--I never even considered doing something like that. However, they seem to miss the point of the dual-stage pump. With the two stages, you should be able to use both plungers in the first stage to fill the PC quickly, because there will be less pressure and difficulty in pumping. As pumping becomes harder, the user reverts to the second stage (or the third one) and can fill the PC with less effort, albeit with a greater amount of pumps.

I am assuming that the slight bends in the middle of the multi-stage plots are where the user reverts to the second stage. Good job on showing the continuation in the graphs. It's hard to notice, but if you look closely, you can see that the lines would get much steeper (as in the standard pump) if not for multiple stages. The partial ease of pumping is exactly what I was trying to explain.

Finally, we come to the reasons not to use multi-stage pumps. Due to differences in dropoff, these pumps truly only aid in the pumping of an APH, barely aid in the pumping of PCgHs, and don't aid at all in the pumping of CPHs. Clearly, one would be better off building CPHs or even PCgHs, as they would show benefits beyond APHs while not "requiring" the complexity of a multi-stage pump.

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Sun Apr 30, 2006 8:28 pm

The graphs do show the use of the stages as you described - as per the animation.

However, I like this other idea... It allows a full stroke with any bore that you use, and less check valves are needed.

I presume this is what your diagram was to show:

Image
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Sun Apr 30, 2006 8:46 pm

@ joannaardway: Your most recent diagram is pretty close to what I wanted. However, I'm wondering if there's a way to build something like it that doesn't require a tube within a tube--but maybe that's what I wanted. I don't really know anymore.

I am going to draw another diagram and get my concept out of my head. It's driving me nuts!

User avatar
Silence
Posts: 3825
Joined: Sun Apr 09, 2006 9:01 pm

Post by Silence » Sat Jun 17, 2006 10:43 pm

I guess I never drew the diagram I promised after all...but I'm thinking along the same lines as joannaardway. The tube inside will have washers or reducers or something in both mouths for proper functionality, although it shouldn't take a genius to figure that out.

Now, the reason I created another post instead of editing my old one is because I found that this idea has been proposed before (and it isn't too surprising). Check out the thread "APH Design," from about a year ago; specifically post 17.

User avatar
joannaardway
Posts: 855
Joined: Mon Feb 20, 2006 10:04 pm

Post by joannaardway » Sun Jun 18, 2006 10:45 am

You'd need to have some screw parts, and some way of locking the outer pump in place for when you are using just the inner pump, but this is a good idea all in all.

(otherwise when you pump the inner one in, the outer one will start moving out.)

It combines the advantages of high and low diameters - which is what everyone wants.
"Over the hills and far away, she prays he will return one day. As sure as the rivers reach the seas, back in his arms again she'll be." - Over the Hills and far away, Gary Moore

"So many people have come and gone, their faces fade as the years go by. Yet I still recall as I wander on, as clear as the sun in the summer sky" - More than a feeling, Boston

Locked