Vintage Double Hose

Our friend Robert up in north Florida sent me this regulator to share. From all appearances it's just a late model long yoke LaSpirotechnique Royal Mistral but INSIDE ??? Click on the dropbox link to see all the pictures

CLICK HERE DROPBOX

Looks like a balancing chamber.
Is there a step inside the main body supports the balancing chamber?
Is the volcano orifice and the stem of the seat the same diameter?
Is the volcano orifice larger than the other Spirotechinque Mistral?

The first two question are required in order to balance the pneumatic forces.

Is there a step inside the main body supports the balancing chamber?
Yes, a very slight step in the body but not as large a step as a Phoenix, Kraken or Titan
Is the volcano orifice and the stem of the seat the same diameter?
Yes, the stem can set on the volcano orifice opening but is just a fraction too large to fit though it.
Is the volcano orifice larger than the other Spirotechinque Mistral?
Substatinally larger and different all together. I put more pictures in dropbox so you could see the difference.

Yes, that is exactly what I suspected. That is a balanced (or mostly balanced) valve.

It is very similar to my Unicorn. I just used the internal valve components from a Conshelf first stage and made the parts I needed.

It is a shame that they used what looks like the exact same levers as the regular Mistral. The Mistral levers work well, but with the balanced valve it would be possible to change the levers to get more mechanical advantage and actually lower the cracking effort. They are not taking full advantage of the balanced valve. So once you rebuild it, you may or may not see a big improvement.

You will probably only see an improvement with a full tank pressure, which in itself is worthwhile.

Someday, when I have more time, I would like to get back to the Unicorn project and have my prototype lever system built. I already have the design and I have talked to Herman to try to build it.

Keep in mind that if you or Bryan ever made a balanced single stage regulator that I would be first in line to buy one. I'd also help finance it, or test dive it, or really do all the easy stuff besides the actual engineering.

If I had Herman's machining skills I would be trying to make a balanced demand valve for one of my single stage regulators! Been on my mind for a long time, and I may yet tear up some perfectly good extra regulator parts trying! Maybe when my garage/shop warms up a bit and I run out of other things to do

This begs the question; "Why didn't US Divers adopt this mechanism instead of fumbling around with their "Royal Mistral" disaster?"