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Neoprene rod stock as piston?

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Neoprene rod stock as piston?

Unread postAuthor: PVC Arsenal 17 » Fri Nov 09, 2007 4:19 pm

I'm currently working on what I hope to be a completely tool-free piston valve. It will serve as a sprinkler valve replacement, and would be easy to build especially for anyone without a lathe (like me).

It will be housed in a 1" PVC tee with a 3/4" outlet. I found that 35mm film cans fit almost perfectly into the part of the tee that is stepped down in diameter to prevent the pipe from moving too far into the sockets. Originally I had planned to use a film can filled with hot glue as the piston, but then that would still require drilling a hole for the sealing face and bolt, plus attaching some sort of bumper.

Since I was still looking to make the construction of this valve brutally simple, I decided against the film can. So I used a caliper to find the diameter of one and it turned out to be roughly 1.25". I then started looking through McMaster for PVC stock or something with the right diameter to replace the film can. I found all kinds of stuff in 1.25", but then I noticed that they also had solid neoprene stock.

It dawned on me that I could kill three birds with one stone if I used neoprene stock:
-I can buy in 1.25" diameter, so there would be no taping involved to get the right diameter.
-It's neoprene after all, so I wouldn't even need to bolt on a sealing face.
-Neoprene is a relatively soft material, so I wouldn't have to make a bumper either.

Has anyone ever attempted this before? The stock found is McMaster part# 8629K131
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Unread postAuthor: jrrdw » Fri Nov 09, 2007 5:09 pm

How much bend would the lenth of a piston have? Would the pressure be enough to bend the piston to the point of jamming? It would need to be lubbed no dought. What lube would last? Whats the over all cost of a pistons lenth be? Or would it have to be bought by the foot and then cut down?
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Unread postAuthor: mark.f » Fri Nov 09, 2007 5:13 pm

You would still have to cut down to length. :wink: So it's not technically a "tool-free" piston.

But it's still a good idea. I don't think rubber would jam since it's pliable and has plenty of force acting on it.
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Unread postAuthor: Novacastrian » Fri Nov 09, 2007 5:14 pm

As long as the neoprene is of the correct hardness i can see this idea working. What pressures were you planning on using? Above certain pressures (my guess around 200psi) the piston might get compacted or "squished" up, causing it to stick in place. (theory only). Would you use an equalization hole or rely on piston by-pass?
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Unread postAuthor: PVC Arsenal 17 » Fri Nov 09, 2007 5:21 pm

Hmmm... never considered that it might compress to the point of jamming. Guess I'll just have to test it out and see.

And supposedly you can cut it with shears... by "tool-free" I really meant
lathe-free. You also need a drill for the back plug's bolts. Who doesn't have shears and a drill? :P
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Unread postAuthor: Novacastrian » Fri Nov 09, 2007 5:29 pm

Good luck getting a nice clean cut. I mould polyurethane and it is very similar to neoprene. It is a cow to cut with any method :x
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Unread postAuthor: Velocity » Fri Nov 09, 2007 5:49 pm

Neoprene is heavy and high friction. I think you would be better off using PVC rod (great stuff). A lot of people dream of tool-free pistons; however, just about everyone has a drill, saw, screwdrivers, etc... so a few basic tools is fine.
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Unread postAuthor: mark.f » Fri Nov 09, 2007 5:57 pm

Then by PVC's definition of tool-less, nearly 90% of homemade piston valves are.

I just wrap duct tape around my pistons until they fit and slide easily with some petroleum jelly. They work beautifully.
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Unread postAuthor: spudgunnerwryyyyy » Fri Nov 09, 2007 6:12 pm

I dont understand why epoxy with a bolt and neoprene sealing face is complicated. Its so simple. Drill thats the only tool u need
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Unread postAuthor: PVC Arsenal 17 » Fri Nov 09, 2007 6:55 pm

That's the thing. I have OCD with 'improvised' things. I don't know why...

I can't even bring myself to build something that requires tape, or casting something out of epoxy. It has to be perfect, or I start freaking out. I spent a long time deciding whether or not to post my tennis ball gun because I held it together with strings before I got hose clamps. Yeah I have problems...

It's not even so much the tool-less part as it is avoiding having to improvise.
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Unread postAuthor: jrrdw » Fri Nov 09, 2007 7:15 pm

PVC Arsenal 17 wrote:That's the thing. I have OCD with 'improvised' things. I don't know why...

I can't even bring myself to build something that requires tape, or casting something out of epoxy. It has to be perfect, or I start freaking out. I spent a long time deciding whether or not to post my tennis ball gun because I held it together with strings before I got hose clamps. Yeah I have problems...

It's not even so much the tool-less part as it is avoiding having to improvise.


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Unread postAuthor: spudgunnerwryyyyy » Fri Nov 09, 2007 8:06 pm

epoxy isnt improvising, the casting process is very perfect in every way talked to jsr. I use pvc filled with epoxy and a o-ring as my piston. o-ring= perfect seal.
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