Where/how to make a plastic piston valve

In summary: Try posting the same question on one of these sites .http://www.model-engineer.co.uk/forums/latest_posts.asphttp://modeleng.proboards.com/board/12/general-chat
  • #1
Seanshine
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I have a project for school and need to make a hand water pump. The thing is, it needs to be a "mini" pump. I will be using 2 mini 1 way check valves and a t fitting, but the problem is i cannot find a way to make the actual piston pump. I also need a spring to draw the piston back up so i can manually push it down with my thumb. I need help with spring rate and how to make the pump in general. I was going to use the famous youtube "how to make a pvc pump" but i cannot find his stuff in a small enough size.

Any insight on where i can buy the peices or how i could make them? The flow of water needs to be similair to a spray bottle
 
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  • #2
(1) Try posting the same question on one of these sites .

http://www.model-engineer.co.uk/forums/latest_posts.asp

http://modeleng.proboards.com/board/12/general-chat

(2) Get a hand trigger operated bottle type spray and use the bits .

Aquarium shops are sometimes a good source of odd things to make pumps from .

(3) Everything you want can be bought but there are problems in getting very small quantities .
 
  • #3
A water pistol pump.
 
  • #4
You can make a piston from any hard plastic. The piston should be free to slide in the cylinder with minimum clearance.
Use a lathe to cut a rectangular groove in the piston. Put a rubber O-ring in that groove.
The O-ring must be big enough to gently touch the cylinder wall.
The groove must be deep enough and wide enough so the O-ring is a loose fit and is not pinched.
Water will move in behind the O-ring and seal the small gap between the piston and cylinder wall.
 
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  • #5
Baluncore said:
You can make a piston from any hard plastic. The piston should be free to slide in the cylinder with minimum clearance.
Use a lathe to cut a rectangular groove in the piston. Put a rubber O-ring in that groove.
The O-ring must be big enough to gently touch the cylinder wall.
The groove must be deep enough and wide enough so the O-ring is a loose fit and is not pinched.
Water will move in behind the O-ring and seal the small gap between the piston and cylinder wall.

This^^

Thanks for the reply. I actually found pvc small enough. But as you stated my problem is the o ring is too tight. Even with all the lubrication i have tried like vegetable oil wd40 and pb blaster its still a shove to get down. Its either too "loose" and the water leaks or its too tight. Any ideas on how i could get it to glide smoother?
 
  • #6
Nidum said:
(1) Try posting the same question on one of these sites .

http://www.model-engineer.co.uk/forums/latest_posts.asp

http://modeleng.proboards.com/board/12/general-chat

(2) Get a hand trigger operated bottle type spray and use the bits .

Aquarium shops are sometimes a good source of odd things to make pumps from .

(3) Everything you want can be bought but there are problems in getting very small quantities .

Theres no places these peices can even be bought in large quantaties! I have checked
 
  • #7
Seanshine said:
Any ideas on how i could get it to glide smoother?
Water is a natural lubricant with rubber and PVC. Lubricate the rubber only with water, anything else prevents the water doing the lubrication.

The O-ring must not be tight in any direction. An O-ring seals because water pressure expands it slightly against the cylinder wall, while pressing it against one wall of the piston groove.

You can make your own special size O-ring by cutting a small part out of a bigger O-ring. To find the ring size needed, rest an oversize cut ring in the cylinder without the piston. Carefully cut of the excess rubber that overlaps. Keep it dry, then carefully glue the joint with superglue if necessary.
 
  • #8
Baluncore said:
Water is a natural lubricant with rubber and PVC. Lubricate the rubber only with water, anything else prevents the water doing the lubrication.

The O-ring must not be tight in any direction. An O-ring seals because water pressure expands it slightly against the cylinder wall, while pressing it against one wall of the piston groove.

You can make your own special size O-ring by cutting a small part out of a bigger O-ring. To find the ring size needed, rest an oversize cut ring in the cylinder without the piston. Carefully cut of the excess rubber that overlaps. Keep it dry, then carefully glue the joint with superglue if necessary.

I have tried everything and it seems like i cannot get it right, i don't have the right tools for anything. I am cutting the grooves with a knife and i always don't cut enough or i cut to deep and it leaks air really bad

Is theyre really no place i could buy this? Its seems impossible that i couldn't cause squirt bottles and water pistols have them.
 
  • #9
What is the capacity that you need to achieve. Is this just a demonstration or do you have an end transfer rate that you need to accomplish.

Strictly for a demonstration my thoughts would be to visit a pharmacist or veterinarian. Either of these would likely have an irrigation syringe. These are typically in size up to 3 or 4 ounces. A quick trip to a store should come up with a compression spring that will overcome the seal of the syringe when lubricated. Adapt this to a tee between two check valves and bingo a hand pump. Clamp it in a holder and fabricate a cam to operate the plunger and there you go mechanical pump.

I was reviewing your original post. Seeing the you only need to approximate a spray bottle I would definitely go with a smaller syringe and maybe look for something that is close in outside diameter so that it could be glued into one of your PVC fittings.
 
  • #10
It would be helpful on the school type projects to know what the goal is for your learning experience. We could help with the calculation of seal friction for your project or we could also help with volumetric calculations. As an engineer often the first and sometimes most challenging goal is to identify your desired result. If you could help us with that we could assist further.
 
  • #12
A hand pump normally uses a cup seal, as seen here,
http://www.clean-water-for-laymen.com/hand-water-pump.html

Same thing usually used for a water pistol, except the cup is a flexible plastic.
Probably the same for sqeegie bottles.
Binding and friction forces are minimized if done correctly.

One could make that with a rod, a metal washer of less diameter than the bore of the cylinder, and a rubber washer (similar to that in your kitchen sink tap) slightly larger than the bore., and a screw.

Or use a piece of leather cut to size so it forms a small cup without crinkling when in the bore, making sure their is enough clearance, plus a bit so it is not tight, between washer and bore to accomidate the leather thickness. Try substituting the metal washer with a rubber washer for flexibility if needed. Add a cup in both directions to obtain doubly acting pump on the up and down strokes.

Into a wooden rod drill a hole in one end to accomidate the screw so that the wood does not split.
Place the washer, then the rubber washer ( or leather ), and then screw to the rod.
Put piston inside bore and enjoy.

You have to experiment with your valves and entrance exit points, with regard to whether you make a single or doubly acting pump.

Take apart a bycycle pump to see how that is made for extra insight.
 
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  • #13
Ketch22 said:
What is the capacity that you need to achieve. Is this just a demonstration or do you have an end transfer rate that you need to accomplish.

Strictly for a demonstration my thoughts would be to visit a pharmacist or veterinarian. Either of these would likely have an irrigation syringe. These are typically in size up to 3 or 4 ounces. A quick trip to a store should come up with a compression spring that will overcome the seal of the syringe when lubricated. Adapt this to a tee between two check valves and bingo a hand pump. Clamp it in a holder and fabricate a cam to operate the plunger and there you go mechanical pump.

I was reviewing your original post. Seeing the you only need to approximate a spray bottle I would definitely go with a smaller syringe and maybe look for something that is close in outside diameter so that it could be glued into one of your PVC fittings.

The syringe is a good idea. But even the syringe doesn't give "spray bottle like" ease with the trigger
 
  • #14
256bits said:
A hand pump normally uses a cup seal, as seen here,
http://www.clean-water-for-laymen.com/hand-water-pump.html

Same thing usually used for a water pistol, except the cup is a flexible plastic.
Probably the same for sqeegie bottles.
Binding and friction forces are minimized if done correctly.

One could make that with a rod, a metal washer of less diameter than the bore of the cylinder, and a rubber washer (similar to that in your kitchen sink tap) slightly larger than the bore., and a screw.

Or use a piece of leather cut to size so it forms a small cup without crinkling when in the bore, making sure their is enough clearance, plus a bit so it is not tight, between washer and bore to accomidate the leather thickness. Try substituting the metal washer with a rubber washer for flexibility if needed. Add a cup in both directions to obtain doubly acting pump on the up and down strokes.

Into a wooden rod drill a hole in one end to accomidate the screw so that the wood does not split.
Place the washer, then the rubber washer ( or leather ), and then screw to the rod.
Put piston inside bore and enjoy.

You have to experiment with your valves and entrance exit points, with regard to whether you make a single or doubly acting pump.

Take apart a bycycle pump to see how that is made for extra insight.
Intresting.. I took apart one spray bottle i had and saw that cup seal that you just mentioned.. Really interesting, the only gaskets and o ring i have ever used were parts for a car like pistons and misc parts. It seems to slide easy since its plastic against plastic, and the cup skirt is a tad flexible. I am still having a hard time understanding how the cup seal makes a perfect seal while the piston rises. Makes sense how the pressure inside would cause the skirt to open and seal while going down.

I read online that to make the perfect seal you glue foam rubber sheets to the piston to make the perfect seal. Witch in theory should work, since it was saying the little air pockets in the foam rubber give room to be compressed when needed, but in my case it seems that the moment it "needed" to compress was on the up stoke thus not creating a vaccume to even hold water in my piston pipe
 
  • #15
Does anyone know where i can find a supplier for water pumps pistons like I am looking for? How did they get it?
 
  • #16
Seanshine said:
Intresting.. I took apart one spray bottle i had and saw that cup seal that you just mentioned.. Really interesting, the only gaskets and o ring i have ever used were parts for a car like pistons and misc parts. It seems to slide easy since its plastic against plastic, and the cup skirt is a tad flexible. I am still having a hard time understanding how the cup seal makes a perfect seal while the piston rises. Makes sense how the pressure inside would cause the skirt to open and seal while going down.

I read online that to make the perfect seal you glue foam rubber sheets to the piston to make the perfect seal. Witch in theory should work, since it was saying the little air pockets in the foam rubber give room to be compressed when needed, but in my case it seems that the moment it "needed" to compress was on the up stoke thus not creating a vaccume to even hold water in my piston pipe
The cup faces the higher pressure.

Foam rubber - use a string wrap around the piston, coat with wax, or impregnate before hand . Do not have any knots touching the cylinder.

You could also try a plunger type piston setup. The piston is longer than the cylinder length, and of lessor diameter than the cylinder so that there is no contact. The seal, or in this case, the packing, is at the top of the piston . Pushing the plunger into the water displaces the water pushing it out. Pulling the plunger out brings waterback in.

You will need to experiment a bit. The first try would not necessarily work.
 
  • #17
Seanshine said:
Does anyone know where i can find a supplier for water pumps pistons like I am looking for? How did they get it?

I do not know about finding the cup seals that are as small as a pistol grip sprayer. I do know that these are common in hydraulics ( repair shops harder to find but wider range) and also in automobile brakes. ( Car parts stores pretty easy to find and often have sets of brake parts for rebuild of wheel cylinders or master cylinders). You can possibly find what you need there. As you search the seals in Master cylinders are typically smaller in diameter you may be able to find something that fits well in you PVC pipe.
 

1. How does a plastic piston valve work?

A plastic piston valve works by using a plastic piston to control the flow of a liquid or gas. When the piston is in the closed position, it creates a seal that prevents the liquid or gas from passing through. When the piston is moved to the open position, the liquid or gas can flow through the valve.

2. What materials are needed to make a plastic piston valve?

To make a plastic piston valve, you will need a plastic piston, a valve body, a sealing material (such as rubber or silicone), and any necessary connectors or fittings. It is important to choose materials that are compatible with the liquid or gas that will be flowing through the valve.

3. What is the process for making a plastic piston valve?

The process for making a plastic piston valve may vary depending on the specific design and materials used. Generally, the steps include creating the piston and valve body, attaching the sealing material, and connecting any necessary fittings. The valve may also need to be tested and adjusted for proper function.

4. Are there any safety considerations when making a plastic piston valve?

Yes, there are some safety considerations to keep in mind when making a plastic piston valve. It is important to use materials that are compatible with the liquid or gas being controlled, and to ensure that the valve is properly sealed to prevent leaks. It is also important to follow any safety guidelines or procedures for handling and working with plastic materials.

5. Can a plastic piston valve be used for high-pressure applications?

Yes, a plastic piston valve can be used for high-pressure applications, but it is important to choose materials that are strong and durable enough to withstand the pressure. It may also be necessary to reinforce certain parts of the valve to ensure it can handle the pressure without breaking or leaking.

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