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Diaphrams!! Pistons!! everyone is using pistons and I never see many good diaphram these days, whats the differnce? why pistons?

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Generally Pistons are easier to make and more common, Im not sure about performance wise but it would be hard to go 4" with a diaphragm I believe. if one was more powerful then the other I would say it would be a piston.

Oh my GOD!!!!!!!! How can you say pistons are easier to make?!?!? A diaphragm is a friggin' circle of rubber!!!!

It depends on what you mean by "more powerful".Efficiency,flow,opening time.There are alot of different characteristics and no valve is 'better' then the other its like comparing a turbo charger to a supercharger there is no 'better' valve.Which ever you choose you wont be disapointed though.

A Piston usualy has better flow but a Diaphram has a vastly quicker opening time.A Diaphram valve would be easyer to build then a piston as there is no need for the building of the piston all that is required is a sheet of thick rubber or similar material.

noname wrote:Oh my GOD!!!!!!!! How can you say pistons are easier to make?!?!? A diaphragm is a friggin' circle of rubber!!!!

I find them easier, I tried a 'phragm and I spent alot of time finding the right rubber thats flexible and to mount it perfectly was a pain, A small piston can just be a piece of wood(some broom handle) with a piece of rubber bolted on.

Diaphragms are material specific, while pistons can be made out of pretty much anything round with a rubber ball or something on the end. The other problem with diaphragms is that sometimes they get sucked out of the barrel.

I just go to the hardware store and buy some 1/8" rubber sheet, it's usually the right flexibility.

well I guess if you know exacly what you need and have a clean cut a diaphram is easier, but if you wanted something bigish like 4" or more I think a diaphram would be easier.

I make my 4" diaphrams from the rubber caps that you get that have hose clamps on them. They are slightly crowned on one side and I put that side againest the barrel outlet. They work great.

I do the exact same thing, never had a single problem.

Diaphragm valves generally open faster, where piston valves open more completely, (don't bounce), because they have a higher inertia due to their mass.

In other words, as much as I like diaphragms, pistons are generally better than diaphragms for large cannons, say, over a 2.5" piston, and diaphragms are better for smaller guns.

Actually QEV's are better for small guns.

Theres two types though, ones a lightweight shaped plastic disk, the other is a rubber diaphragm.

Just to keep the piston/diaphragm debate going into QEV's

And QEVs use diaphragms, which you've just explained, and you also said they're better for smaller guns, so I win.

Ah but the other type of QEV uses a lightweight rigid plastic disk which is specially shaped and that could be called a piston...