Pistons are useful for many things in today's world.  For example, internal combustion engines that run our cars use pistons.  Pistons can also be used for hydraulics, pneumatics, pumps, and other devices of all shapes and sizes.  The possibile uses for pistons is endless.  However, it is very difficult if not impossible to make a perfectly sealed piston for your everyday projects.  In this Instructable I will show the process I used to make perfectly sealed pistons for PVC pipes, and how I used a piston to make a simple airgun.

A video of the airgun can be found here: http://www.youtube.com/watch?v=WGaR2vzxUu8
I had a lot of difficulty getting the video to embed properly, even though I have not before.  If anyone has a tip, let me know!
Webster's Definition of "piston": a sliding piece moved by or moving against fluid pressure which usually consists of a short cylindrical body fitting within a cylindrical chamber or vessel along which it moves back and forth
See source here: http://www.merriam-webster.com/dictionary/piston

Here's an overview of what will be explained in the following steps:
  • Step 1:  Materials Needed
  • Step 2: The Build: The Secret to the Perfect Piston
  • Step 3: The Build: Piston Pictures
  • Step 4: Simple Airgun Theory of Operation
  • Step 5: The Build: Simple Airgun
  • Step 6: Conclusion

Step 1: Needed Materials

Not many materials are needed for this project.  The list is as follows:
  • PVC Pipe - (pic 1) - You can use whatever diameter you would like.  In this project, I use a length of 1" Inner Diameter Schedule 40 PVC for the outer part of the piston.  For the inner piece that seals against the 1" pipe, I used 1/2" Inner Diameter Schedule 40 PVC.  PVC pipe is available at any big box home improvement store.
  • Foam Rubber Sheet - (pic 2) - I bought this sheet at my local craft store.  It is very cheap, and comes in a variety of colors and thicknesses.  In this Instructable I am using black "Foamies" brand sheets that are 3mm in thickness.
  • Hot Glue Gun - (pic 3) - Everyone has to have one
  • Dremel or Rotary Tool - (pic 4) - I use my Dremel for nearly every project.  Optional, but very helpful.
  • Hacksaw - (not pictured) - I used this to cut the handles for the airgun I used the piston for.  Optional.
<p>By the way: http://www.instructables.com/id/Potato-AirGun/</p>
Same concept. Thanks for sharing!
well done. ive always wondered about how to make good pistons with out messing around with o-rings. there we go. i might use this idea in an upcoming project... so sad i missed this years Launch It! challenge (and last years, and so on)<br><br>well done. i recommend shooting potato plugs or marshmallows.
Thanks!! I've struggled with the O-ring problem as well, which is a big part of what prompted this project. I could easily shoot potato plugs with this gun as-is, but I'd have to make a different barrel to shoot marshmallows. <br> <br>Thanks for commenting!! : )
Nice. Btw, i have a question and a fix for your marshmallow thing. <br> <br>Q-Do you know something else i can use instead of the foam rubber. <br> <br>C-Maybe you can get one of those bellish-shaped reducers, and a smaller diameter of PVC. Use the PVC cement with those. Then when u want to use it you can just put it on, like an attachment.
In answer to your question, there's a lot of things you could use instead of foam rubber. Regular riveter Sugru would network good ones.the foam rubber just made it way easier to get an airtight seal. Your solution to the marshmallow issue is a good one, I can't see any issues either other than maybe scratching the paint.<br><br>thanks for commenting!! : )
i am almost done making a rife based on this concept, and will probably have it done in time for the Challenge! i will of course site you as the inspiration for the seal design.
That sounds great!! I'd love to see the finished project. Feel free to post a link to your project here as well : ).
Here you go! I'm afraid it is really sloppy because i had to use a terrible camera that would just not cooperate. anyway, you can still understand it. <br><br>http://www.instructables.com/id/The-Potato-Piston-Rifle/<br><br>here is also a picture of the finished gun
Awesome!! The pictures are actually pretty good considering the camera used. It looks like a fun project, and thanks for mentioning me in the Instructable : )
no problem.
i want to make a DiY nerf gun for a competition. my qeustion is will i be able to use this inside the nerf gun or not?<br><br>P.S. sorry for my poor english
You would definately be able to use a piston design like this one to build a nerf gun, since it can be scaled up or down to any size. <br> <br>Thanks for the comment!
could you use nerfs
As projectiles? Absolutely! Just as long as the barrel is the correct diameter. <br> <br>Thanks for commenting! : )
where the nipples do i get foam rubber?????
I found mine at the local craft store. You should be able to find it at craft/hobby stores like Michael's or Hobby Lobby.
whats the texture like as ive never used the stuff?
That's actually pretty hard to describe. It's sort of like a sponge, but with holes so small you can't tell that they're there? It's soft, light, somewhat squishy..
This looks like a simple, elegant way to create a seal. Have you done any tests to see how much pressure the foam seal can hold? I have been holding off on a PVC project because I need to find the right O-rings. If you haven't tried higher pressures, I might invest some time and experiment with this.
Thanks!! I have not done any tests with higher pressures, although I would really like to. If anything, high pressure seems like it would be the downfall of this method. <br> <br>Thanks for commenting! This has been entered into the Launch It! Contest by the way : )..
embedded<br> <div class="media_embed"> <div class="media_embed"> <iframe frameborder="0" height="349" src="http://www.youtube.com/embed/WGaR2vzxUu8" width="425"><br> </iframe></div> </div>
Thanks : ).. I copied and pasted the embed code from youtube like I always do and it didn't work for some reason. Did you do anything differently? <br> <br>Thanks for reading and commenting : )
no, that's exactly what I did. maybe it works in comments only?
Hmm. That's interesting, I'll have to try it again. Thanks!
<br> Well, to make my water pump may take a bit long time. I am a farmer and we are living the middle of the summer here in Turkey. I have alot to do now, but winter time is good for instructables. <br> <br> Best....
<br> Yes ! Thank you for the way to make it. <br>I'll use the same system for my water pump now ! <br>Thank you !
Excellent. When it is done, post pictures of the finished project if you can! Thanks for commenting! : )
Awesome gun!
Thanks! Thanks for commenting : )

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Bio: I am currently a mechanical engineering student at the University of Toledo, and the founder of the University of Toledo Maker Society. I have a ... More »
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