I worked on this all weekend and I've machined the parts for 4 valves. I've fully assembled one and done some preliminary testing, so far it looks good. I promissed some pictures. The first picture on the is the Ryobi drill taken apart.
The next picture is the set of machined parts nevessary to turn this into a valve driver. The part on the left consists of a custom piece bolted to the remanats of the drill chuck that was turned down.
The next picture is an assembled valve.
The motor power wires are on the left, the small wires exiting the top go to the magnetic position sensor that sense a small magnet glued to the top of valve shaft. I've built for of these. When I get the electronics to operate them done I'll test one with LN2 and see how they work.
The finished valve weight about 1100 grams.
The machined parts are about 170 gm and the just the motor without any thing else is 350.
so there is some room to use a better (brushless ) motor and trim some weight.
The final valve could probably end up under 1Kg.