Piston valve help again

[Procrastinator]

Hi again, I just finished my piston valve and gotten really bad results (100psi shooting a battery 3 metres) I thought the problem might be the piston being too short leaving alot of space for the piston to move back, but I put a new washer further forward behind the piston and it still continued to blow 75% of the air though the pilot. I really can't figure this one out, could someone give me some advice? I think I'm just going to buy a QEV. Here is the basic setup of my Piston valve if it helps. (MRR's plans)
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[jvw1979]

Maybe some more experienced guys can pitch in as well, My first valve had the same issue, turns out it wasn't tight fitting enough so a lot of air were allowed to escape through the pilot as it seeps around the piston.

Don't know the tolerances on your piston, but try a few turns of tape around it to get it more "snug" and try again.

[Procrastinator]

Don't know the tolerances on your piston, but try a few turns of tape around it to get it more "snug" and try again.

Thanks for your reply.
The piston is a perfect fit in the tube apart from the equalization ridge I cut out. If I taped it, the piston wouldn't even fit in the tube

[jackssmirkingrevenge]

your piston should fit this description:

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the equalization ridge I cut out.

There's your problem.

No o-ring = no need for equalisation holes

[Procrastinator]

No o-ring = no need for equalisation holes

Darn, I was kinda wishing it wasn't my piston. How could have MRR's have worked then?

[daniel0663]

Have you tried using a larger pilot vavle? e.g. 1/2" or a 1/4" ball valve.
There might be lots of problems/manfunctions which may contribute to this problem.

I don't think it may be the piston tolerance, unless the piston is dramatically undersized, which will cause all kinds of sealing issues in the first place.

Your piston seems to be the same length as the nipple so i don't see any problems there.

I presume the hose is your "air tank" which you use to help you maintain a muli-shot, without refilling.

If it is, you have a exceeding amount of pilot volume ( air volume behind your piston ) which JSR will happily go over the problems relating to pilot volumes which may be the problem in the first place...

also, is that a nail holding the rubber againts the piston?
if it is, you are rebellious, not to mention it is dodgy

[Procrastinator]

also, is that a nail holding the rubber againts the piston?
if it is, you are rebellious, not to mention it is dodgy

Yeah it is, That was the result of my failed attempt at using epoxy

I presume the hose is your "air tank" which you use to help you maintain a muli-shot, without refilling.

That was my original idea in which I ran into another problem the threads were all wrong.

[MrCrowley]

While in a perfect world that closely resembles jackssmirkingrevenge's workshop, one could pilot such a piston with a blowgun but without o-rings and the large pilot volume you're probably best going with a 1/4" ball valve.

Usually, it is a combination of a bad fitting piston with a small pilot valve but you can have the worst fitting piston and the largest pilot valve and see sh|t results whereas you can have an excellent fitting piston and only see slightly worse results and perhaps a small delay in firing with a small pilot valve.

Tip: Buy some lubricant, it will help seal the piston around its edges.

[jackssmirkingrevenge]

While in a perfect world that closely resembles jackssmirkingrevenge's workshop

I'm running out of space to support my compuslive accessory buying habit!

[Procrastinator]

New piston is setting. Hopefully with the help of a little lubricant it will work.

[Crna Legija]

what in the last pic is your tank the fire extinguisher? and its connected by hose, if so id say thats your problem.

[Brian the brain]

I see a couple of problems.

The pilot volume is massive.
Even more so when compared to available chamber volume.
The chamber should be the elephant, pilot volume should be the mouse.

That hose is a well known snake: Floa Constrictor..
So the volume is really only restricted to the valve itself.

I can see light passing between the piston and it's housing.
Not what you would call " Toight like a toiger" now is it?

You don't need the airchannel.If it slides there is enough room for air to pass.

So throw out the snake, and bring in the tiger, have the elephant ready to fight the mouse and you're ready.



And Jack...leave me out of this.
I'm in a bad mood 'cause I lost my mustache in a nasty ssssssmelting accident!

[jackssmirkingrevenge]

I'm in a bad mood 'cause I lost my mustache in a nasty ssssssmelting accident!

How will people know you're Dutch now

[Brian the brain]

Cause of my wooden shoes.
Mine are painted in metalflake.

I looooooove metal.


Call me steelmember...

@Procrastinator:
I suggest using a bolt and washer type piston.
That way you can bolt on the sealing face.Much stronger.

[Procrastinator]

I can see light passing between the piston and it's housing.

That isn't light its blue teflon tape I forgot to remove
EDIT: That isn't my piston either, Its the rubber washer I put infront of a metal washer.

About the chamber, I didn't plan for that huge volume. I bought the fire extinguisher then found out the threads weren't 3/4 so then for some stupid reason I decided to attach it with a hose

I will buy some 3/4 pipe to make the chamber. The piston I was thinking about but that's for another day.