This Will Blow Your Minds.

Build a homemade water gun or water balloon launcher and tell us about it.
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AMDAthlon
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This Will Blow Your Minds.

Post by AMDAthlon » Tue Jul 04, 2006 3:53 pm

After about a month's worth of work I have decided to go chasing after a different homeade design. After hours of math and a little inspiration from the boards I now have my own complex design that should be a small revolution.

I will not divulge all until after the construction is completed and the design is perfected. However I cannot keep this out of the public light. My concept is for a tracked twin cylinder dual compression chamber pump. Here is how the concept works:

Image


Where everyone should note that the red denotes the cylinders, green denotes seals, yellow denotes solid endstops on the second cylinder, and the purple or pink denote check valves for intake or output....

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wetmonkey442
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Post by wetmonkey442 » Tue Jul 04, 2006 5:12 pm

That'll be one heavy pump with all of those check valves. Good luck on your construction, and please don't hesitate to update us.

Soak On

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Silence
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Post by Silence » Tue Jul 04, 2006 6:31 pm

Maybe good in theory, but there are a few things to be ironed out. It's nothing more than a non-tracked two-stroke pump combined with joannaardway's final design of a dual-stage pump. However, you will need to be sure to make the O-rings for the internal pump looser than those for the external pump, or the pump might not function correctly.

Also, I really don't see the need for two O-rings on the inner pump shaft, as one will serve just fine. If you're worried about stability, it's just like a standard non-tracked homemade pump--tight electrical tape on either side should make the entire thing very solid. However, wetmonkey442 has a point about the weight--and it might prove a problem especially in the light backup homemades that I plan to make that will use two-stroke pumps. These notes aside, good luck with the further development--you would be the first to make each type if you do it soon.

AMDAthlon
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Post by AMDAthlon » Wed Jul 05, 2006 10:12 pm

The design has everything to do with the tooling that I have at my disposal. I would advise anyone who thinks that weight is an issue to redefine their view of a check valve or to buy a few small ones from McMaster Carr. When you are thinking about check valves think small being less than a quarter inch inside diameter and an inch long. Flap type check valves can be homeade with old inner tube for less than fifteen cents each and less than two grams worth of weight. PC-11 Marine Epoxy by Loctite Corporation produces great plastic to rubber anchors. In other words attach a 0.5 inch by 0.75 inch piece of inner tube over a quarter inch hole and use the epoxy to attach approximately one third of the rubber section to the pipe. Make sure the flap can move back and forth freely. Depending on which side of the pipe you put your flap on determines the directionality of the medium moving through it. When pressure is applied the flap should shut firmly against the contact surface.

Also consider the usage of tape. It is a temporary seal but not one that lasts.
The O-Rings are a more suitable solution. If you have a lathe that can be easily tooled I would recommend aquiring a thin piece of high speed tool steel, adjusting the rake angle accordingly, and creating the grooves for the O-Rings. As for the design calling for two O-Rings I like solid compression. Not only that O-Rings are cheap. Ask yourself "Why not?" Overbuilding something is the trait of an engineering mind. Besides if one fails you have a reserve. If one is overly concerned about stiffness in the pump the grooves can be adjusted and the addition of silicon based greases can be of benefit.

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joannaardway
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Post by joannaardway » Thu Jul 06, 2006 9:06 am

"It is a temporary seal, but not one that lasts" - Ermmmm..... Possible rewriting needed.

Flap type check valves will not hold the pressures you need to create.

I would advise against this design - the two designs will not merge well. You will nullify the advantages of the dual stage with the two stroke.

A higher pump bore makes it harder to pump - and pumping on the outstroke is incredibly hard... So both together will make the concept extremely difficult to use.
"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

AMDAthlon
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Post by AMDAthlon » Thu Jul 06, 2006 6:55 pm

The whole application of the design is to quickly build a large volume of air then bring it to higher pressures with the smaller inner bore. This is why I merged the two designs. One piston slides inside the other when higher pressures are achieved. Bores can be limited. The current prototype I have built is one inch with a smaller half inch cylinder inside. So far the highest pressure I can get is somewhere around 40 PSI but I have not pushed my pump due to it's construction. In essence do not use DWV pipe to build this design.

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joannaardway
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Post by joannaardway » Thu Jul 06, 2006 7:09 pm

Yes, but the inner bore will move first....

Thus invalidating your point...

Hang on, why are you pumping air with 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

AMDAthlon
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Post by AMDAthlon » Thu Jul 06, 2006 7:51 pm

The inner bore is supposed to move first. When you want the full bore of the pump to move volume you can get it but when you want pressure you can use the inner bore only sliding inside the larger cylinder to build pressure. Keep in mind that the yellow points of the larger cylinder are smaller than the bore of the smaller cylinder as to keep it inside and once the pump is extended to a certain point to engage the larger cylinder as to have the full bore. I am only pumping air to see how well I have my design tuned. It might also have something to do with the design of my water gun. I am chasing air pressure but one should assume the medium the pump is moving could be water.

On another note I was trying to place emphasis on the fact that tape was not a good choice for a sealing medium. Sure it makes a great temporary seal but it will not last thus making O-Rings more favorable.

If anyone is curious to the bore sizes I am working with try 0.75 inches on the small bore and 1.5 inches for the large bore. Of course these can be changed if anyone else is trying to produce a working pump of this design.

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joannaardway
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Post by joannaardway » Thu Jul 06, 2006 8:26 pm

Are you serious?

.75" is a max for a usable pump - 1.5" will be virtually unusable - unless you are secretly the governor of california...

This design style was discarded for rather good reason. - You will be forced to use half strokes for high pressure work, which will get annoying.

And the human frame cannot exert as much force on the outstroke as the instroke - thus defeating the point of the dual stage pump.

The aim of the dual stage pump is to allow a lower bore pump to allow the pressures a high bore pump can't.

By making it two stroke, then you cannot achieve what the dual stage system is capable of - unless you have some method of "turning off the second chamber"
"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

AMDAthlon
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Post by AMDAthlon » Thu Jul 06, 2006 11:34 pm

Short strokes can be eliminated by increasing the length of the large bore cylinder. I have a eighteen inch long pump not counting the endcaps which contain the checkvalves. The larger bore cylinder can move four inches in either direction and the smaller bore cylinder can move up to fourteen inside the larger bore cylinder. I definitely do not consider this a short stroke given that most Super Soakers only average about six to ten inches.

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wetmonkey442
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Post by wetmonkey442 » Thu Jul 06, 2006 11:52 pm

I look forward to seeing the construction of this design. In my mind, the weak link is the check valves. However, I am willing to trust your opinion, and will look forward to pictures and/or construction updates.

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Silence
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Post by Silence » Fri Jul 07, 2006 12:48 am

I'm afraid I'll have to support joannaardway on some of your claims. In fact, if you look at the design closely, you'll notice that no matter which direction you're pumping in, the small bore will always move first! A short bore section on the instroke is a large bore section on the outstroke, and similarly, a large bore section on the instroke is the small bore section on the outstroke. Thus, there is no way to actually be able to use this effectively.

I was surprised when you first suggested a 1/2" and even a 1" pump--that's four times the area of the smaller bore, which means you can only use it for 1/4 of the pressure (and much less than 1/4 of the time). Needless to say, that really isn't worth it--the 4/9 of the pressure from a 3/4" pump is preferable for me in most situations, although your priorities might differ. I didn't even have time to respond to that before you proposed a 3/4" and 3/2" pump--that is simply ridiculous! As joannaardway said, you would need to be as strong as the Terminator in order to generate enough pressure. In fact, if you could only get about 40 PSI with the 1/2" one, then either (A) your design already has some serious flaw somewhere (bad) or (B) you're not nearly strong enough (bad, especially so with a 3/4" pump).

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joannaardway
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Post by joannaardway » Fri Jul 07, 2006 8:53 am

Having different stroke lengths for the high and low bores?

Based on the amount that the larger bore can actually do over that distance - why bother? It's just more to go wrong, and:

Assuming 1/2" and 3/4" over 4 inches - it will add a pitiful 16ml to the stroke (based on the extra effort added), and may well "jam" the pump due to the increased force required.

An 18" stroke on a 1/2" pump offers almost 60ml per stroke - and has no risk of "force overkill"

Anyway - I came up with a quick experiement - and gave it to my twin (who has recently put on a little over 2 stone of muscle so he's not exactly lacking in the power department)

He could only exert about half the force on the outstroke - if that. I could beat his outstroke with my instroke...

With a two stroke pump, you double the pressurization speed, but halve the pressure you can reach.

That is an incredible loss of power involved. Do you want to go to extra effort, for less power and range?
"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

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