<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div></div><div>Hank,</div><div>there is a flaw with the Bellows Add system that I can see, in that if you</div><div>have an air leak that increases the cabin pressure then the Bellows Add</div><div>system won't add O2. </div><div>Ultimately you are relying on your O2 sensor & even then O2 sensors</div><div>have a large failure rate & a life expectancy.</div><div>Rebreathers use 3-5 sensors for redundancy & compare signals.</div><div>For a large sub you have a lot more time for any failure to have an effect</div><div>than you would in a sub like your 1 person or Cliff's. </div><div>Maybe if you insist on a Bellows Add system, have an extra O2 sensor.</div><div>The second stage regulator works the opposite way than what you want</div><div>with the water pressure pushing on a thin diaphragm that has a lever the</div><div>other side that opens the valve. Maybe if you glued the lever to the inside</div><div>of the diaphragm you could open a valve with it. You would only use the </div><div>regulator valve though, as the rest would be useless.</div><div>Better still, make a small sealed enclosure with a diaphragm on one face</div><div>& attach the second stage lever mechanism to the outside against the diaphragm.</div><div>That way you could make a screw in / out fine tuning adjuster as per DW.</div><div>Alan</div><div><br></div><div><br>On 25/05/2020, at 1:50 AM, hank pronk via Personal_Submersibles <<a href="mailto:personal_submersibles@psubs.org">personal_submersibles@psubs.org</a>> wrote:<br><br></div><blockquote type="cite"><div><div class="yahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div dir="ltr" data-setdir="false">Hi All, I am looking for ideas on how to make a automatic O2 feed similar to the DW bellows add. I want a non electronic system. I was thinking about a scuba second stage regulator conversion, that senses negative pressure to release O2. Sean???</div><div dir="ltr" data-setdir="false">Hank</div></div></div></blockquote><blockquote type="cite"><div><span>_______________________________________________</span><br><span>Personal_Submersibles mailing list</span><br><span><a href="mailto:Personal_Submersibles@psubs.org">Personal_Submersibles@psubs.org</a></span><br><span><a href="http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles">http://www.psubs.org/mailman/listinfo.cgi/personal_submersibles</a></span><br></div></blockquote></body></html>