The ball valve is a 1'' and I bored out the end with a drill press a slight bit to have it fit a standard double hose mouthpiece cage. Here is a link that will more or less walk you through the process.
http://www.atlimp.com/rguwob.htm
You will notice that he glues the pvc pipe mouthpiece to the exterior of the ball valve. I instead fitted the pvc pipe with the help of a heatgun to fit inside the drilled 3/4'' hole for less bulk. Just a little pvc glue and its a smooth transition. If there is anything I am leaving out please do not hesitate to ask questions.
The following were found on the web...
If any of you have access to some machinery something in this ballpark could be a possibility. I am thinking about experimenting with an exhaust valve similar to the one in the picture below.
Here is a link for the DSV on the Azimuth rebreather pretty compact
http://www.nobubblediving.com/azimuth.dsv.htm
and another home build
http://www.ppo2.com/mouthpiece.htm
Another...
This is not at all vintage, but for the true solo divers out there that want a safe second...
