SpudFiles

I'm making a cannon and using a qev. I plan to fill it with a schrader valve. Do I need to add a ball valve there because I heard that sometimes qev's can be piloted just by the air comming out when you pull the hose off the schrader valve.

I had the same thought about the schrader activating the pilot on my up and coming high pressure gun. It would be a serious hazzard if that were the case. I was going to use a blow gun but Jack reckons that the schraders work fine.

Yes, they can be piloted, but sometimes they may only half open and the air will kinda leak out the barrel. Also my old bike pump likes to leak a little air sometimes and that can even stop it from sealing.

EDIT: 777th post 8)

but has anyone actually had it happen to them?

I heard that sometimes qev's can be piloted just by the air comming out when you pull the hose off the schrader valve.

If your pilot volume is small, then yes it can happen.

I had the same thought about the schrader activating the pilot on my up and coming high pressure gun. It would be a serious hazzard if that were the case. I was going to use a blow gun but Jack reckons that the schraders work fine.

Whoops, here's something I forgot to mention What I do to get around this is to put an o-ring between the schrader and the attachment on my shock pump. This means that the stem of the schrader isn't being pressed down and effectively acts as a check valve, being opened only by the pressure of the filling air. This means that when I disconnect the fitting, the schrader is already closed and no air is lost from the pilot chamber.

what do you use to push the valve inside with?

jon_89 wrote:what do you use to push the valve inside with?

You don't have to push it in - the stem is only held in place by a weak spring, so if the air pressure your pump or compressor is putting out is greater than that in your chamber, it will still pass through the schrader.

cool i will have to try that sometime thanks jsr

point taken