100% seal, no O-rings!

[Brian the brain]

I took a long look at the rubber diaphram in bike pumps and decided to use that to build a better piston.The phram works like a one way valve and allways ( a good one at least) seals a 100%, because it expands towards the tube walls under pressure.

Things you need:
Electric drill
Vice
Sandpaper
Disposable knife blade from a utility knife or a razorblade


First, cut a thick neoprene sheet into a circle slightly larger than the piston housing.Put a threaded rod through the middle and clamp it in with some nuts.
Put the rod in a basic electric drill.
You now have half a lathe.
Put the blade in the vice , with only about 2 mm of the edge sticking out.
THis will be your cutter.

Spin the drill at maximum velocity and gentley ( sp?) start grinding the neoprene circle straight on top of the blade,pushing it onto the vice. BUT WITH THE DISC AT AN ANGLE!!
This way the sheet of neopren becomes tapered.

You will need to practice this and learn to hold the spinning drill in just the right spot to avoid the whole thing starting to bounce.It should feel smooth if you do it careful enough.

This way you can shape the sheet anyway you like.
The idea is to end up with a smooth tapered shape.Finish it off by spinning it perfectly smooth on fine sandpaper.
You do the same thing with a slightly smaller diameter neoprene disc to fit INSIDE the barrel.
It MUST however still be slightly oversized.

With these two rubber discs you can now make a piston wich seals perfectly INSIDE the barrel, and wich will allow filling from the backside, but will not allow any backflow.This will cause a very powerfull pop when discharged.The front "barrelphram" can NOT be used without the back one.Without the back the front can NOT be pulled out the barrel because of the pressure on the front causing friction.
Feel free to build your own, just don't forget who came up with it!

Below is an example.I forgot to add a stopper in the pic to stop the piston from going into the barrel too far, but those of you who think this idea through will get what I mean, and see the potential.
I showed the middle washer with big holes in it, so effectively the chamber gets bigger.
The upper pic should explain how to spin the phrams into shape.

[VH_man]

Nice. thats truly ingenious. have you tested that thought? I can see the air slipping right past those neoprene disks.

[Brian the brain]

The discs should be slightly larger than I showed in the pic.I just showed it like this to show off the tapered edge.
When the discs are bigger they bulge and seal off the pipe completely.
They can't flip over to let the air out because of the metal washers.They are pressed into place, sealing the edges.
I have tried it, it works like a charm.

[iknowmy3tables]

thats pretty nice, the diffrent sized diaphrams in the valve confuse me, but Ive seen some sanding disks that might work

[Brian the brain]

What??? Sanding discs don't seal.

The different size has to do with the workings of a piston valve

[experament-u2]

that is awsome and looks pretty easy maybe i might be able to make a piston valve that woks

great how-to as well nice clean images

[Hotwired]

What??? Sanding discs don't seal.

Wonder if I can make signature room for that one

Back on topic: looks like a great and very workable idea but as with the bike pumps its found in it'll need greasing (not oil) to slide and seal as it should or you'll get friction wear.

[iknowmy3tables]

I still dont get the tee valve, is the chamber opening from the bottom, if so how could air dumping behind the smaller disk be enough to pull the larger disk since it has more surface area where presure is aplicated to make it move left,
I'm just a little confused

[Brian the brain]

Yes you are!
Very confused!!
And to think you are so close!!
If a small surface can not pull away the larger one.....would it be possible
the larger surface is supposed to pull away the smaller one???
DUH!!

Sorry to ridicule you..it's all in good humor.
The bottom is the inlet from the reservoir, the left side is where the barrel is, the pilot area ( wich empties through a valve) is depicted on the right.

[iknowmy3tables]

oooohh whoops

[jjk92]

sorry for my ignorance but i couldnt find the answer in the wiki or anywhere else but are all 3 washers if not what is each one ? thank you

[Brian the brain]

All metal washers.

[sgort87]

VERY NICE! I had my doubts until you said you had done it successfully.

This is a real neat design. The only thing I can see is that the pack of the "piston" has a very large area.

I wonder how this would perform if one were designed so the piston's sealing side would simply release from the back end. No pilot. No "opening time" involved. Just a lot of remaking sealers.

This gives me an idea... The projectile makes the seal. That would get time consuming to make all the ammo/sealers if it were fired often.

[MrCrowley]

I wonder how this would perform if one were designed so the piston's sealing side would simply release from the back end. No pilot. No "opening time" involved. Just a lot of remaking sealers.

Do you mean the back of the piston would be fixed in place but the front washer with the modded washer that seals the barrel 'slides' back and forth when acuated and filling the gun like a supah or something?

[sgort87]

No, I mean you actually let go of the sealing assembly and launch it.