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DIY PVC piston?

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DIY PVC piston?

Unread postAuthor: Hurricane Air Arms » Mon Oct 08, 2018 6:17 am

Hey team, struggling to find a way to precisely create a PVC-on-PVC piston.

It has to be PVC on PVC because I need it to glide and seal pretty darn well. I've found some couplings that fit pretty close inside the 25mm PVC but without a lathe or pro routing tools... it's hard to get anything close.

So I'm going to do some DIY work but in the meantime, without buying a footpump, how do I build the perfect PVC piston?

3D printing doesn't have the integrity to build a tough enough cylinder, even if precise.

I also want to avoid excessive O-ring contact, don't want to burn out the seals.

Any suggestions or tips?
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Re: DIY PVC piston?

Unread postAuthor: Cthulhu » Mon Oct 08, 2018 9:38 am

Have you considered 3d printing an adapter to fit inside a section of PVC pipe so that you can use a regular drill to turn it?
Even more advanced would be to use bobwombles 3d printed 3 jaw Chuck to hold a coupler or section of pipe to be turned.
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Re: DIY PVC piston?

Unread postAuthor: jackssmirkingrevenge » Mon Oct 08, 2018 11:32 am

Hurricane Air Arms wrote:without a lathe or pro routing tools... it's hard to get anything close.


epoxy casting is your friend!
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Re: DIY PVC piston?

Unread postAuthor: hectmarr » Mon Oct 08, 2018 11:34 am

I made them from epoxy resin or polyester resin. They come out perfect when using a mold. If you leave a hole well centered, and then, when the curing is finished, temporarily stick a metal shaft, and make the slot for the oring in the side hole-making machine. I use it in a 5X hybrid, and it has not been destroyed until the present. You can try it, if you think it's convenient for your project.
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Re: DIY PVC piston?

Unread postAuthor: Hurricane Air Arms » Tue Oct 09, 2018 7:16 am

Cthulhu wrote:Have you considered 3d printing an adapter to fit inside a section of PVC pipe so that you can use a regular drill to turn it?
Even more advanced would be to use bobwombles 3d printed 3 jaw Chuck to hold a coupler or section of pipe to be turned.


Many times. But due to the nature of 3D printers regarding layering, I was advised that these types of pistons woudln't hold up to the pressure and force exerted.
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Re: DIY PVC piston?

Unread postAuthor: Hurricane Air Arms » Tue Oct 09, 2018 7:21 am

hectmarr wrote:I made them from epoxy resin or polyester resin. They come out perfect when using a mold. If you leave a hole well centered, and then, when the curing is finished, temporarily stick a metal shaft, and make the slot for the oring in the side hole-making machine. I use it in a 5X hybrid, and it has not been destroyed until the present. You can try it, if you think it's convenient for your project.


So apparently a friend of mine says a two-part epoxy injected into a mould (say, an off-cut of PVC pipe) works well. The epoxy dries hard and solid, and is kept from sticking using linseed oil? Very interesting! Huge info. The piston I'm building must be able to do a similar job to a high-end foot-pump and I think you hit the nail on the head regarding this mould idea.

Thanks!
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Re: DIY PVC piston?

Unread postAuthor: jackssmirkingrevenge » Tue Oct 09, 2018 9:15 am

kept from sticking using linseed oil


I would suggest a very thin layer of grease, less chance of it mixing with the epoxy.
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Re: DIY PVC piston?

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Re: DIY PVC piston?

Unread postAuthor: keks2033 » Tue Oct 09, 2018 12:55 pm

The valve for tubeless wheels is well suited to the role of a piston, the diameter is just 25 mm. Image
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Re: DIY PVC piston?

Unread postAuthor: keks2033 » Tue Oct 09, 2018 1:26 pm

I also did it like a pump piston. Image Image
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Re: DIY PVC piston?

Unread postAuthor: Hurricane Air Arms » Wed Oct 10, 2018 10:21 am

I’m pleased.

I went ahead today and bought two part epoxy putty, unfortunately the wrong type (steel). You would think a warm mouldable substance would curate like crumbly play-doh, wow, how wrong was I?

This stuff cured, WARM, in about 15 minutes and after an hour, was virtually indestructable. Impressive. I think the reason I stayed away from epoxy was because of the nature of it as a repair and patch-up solution- Never in my wildest dreams did I think you could mould your own piston (there are approx. 2-3 vids on youtube showing people cure their own plastic epoxy pistons!)

I know I’m harping on, but to me without a precise piston, every airgun I plan to build won’t function. This has also been a severe barrier regarding my spudding desires because like anything, without a key component, you won’t have anything else. Hell. I can’t even take measurements or plan the rest of an airgun because without the piston, or testing the initial design, I won’t know if it’ll work! :(

Alas, you can buy PVC-suitable Epoxy Putty. This is purely amazing to me. And to believe I was trying to find stock PVC that would magically fit...

Thanks again! This has helped get my project back on track.
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Re: DIY PVC piston?

Unread postAuthor: hectmarr » Thu Oct 11, 2018 10:47 am

Good news that this home technology is useful for your projects :) Liquid epoxy resins, for laminating, also work very well. They are two-component and it is very easy to make it take the shape you need. regards
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