I need to build a propane valve that can be actuated by an RC servo. This means that the range of travel of the controlling surface is limited and the force needed to open and close the valve should be low.
Due to the travel limitation, I cannot use a screw type valve (see attached drawing) where it's just a brass needle pressing onto a hole when closed.
With a low travel distance, e.g. 5mm/0.2", the torque from the servo would be higher than with a longer travel distance. The force the servo can press or pull at 5mm/0.2" distance would be something like 5-10kg/11-22lbs.
Propane pressure would be no more than 6bar/87psi.
I'm thinking that it should be a valve type where the pressure from the propane would close the valve so the pressure would help seal the valve. But then this might also prevent the servo from opening the valve due to the limited force of the servo.
I have been thinking about a design as attachment number 2, simply a pin that goes into an O-ring and seals off the propane flow. Would this work? Or would the O-ring be a weak link? What would happen if liquid propane would enter by accident, would it block up the movement of the pin into the O-ring? I would of course have something that keeps the pin from shooting out to the right.
Another idea comes to mind. I will be using the type of propane canister with a built-in valve (Lindal B188 valve), it's those EN 417 threaded canisters. That valve needs to be pressed down for the propane to flow, and is pressed when you attach your device to the canister. But maybe I could make the servo push that valve pin down and open up the flow that way.
Please add your comments to this
The lighter is way too small (not enough flow) and the pressure range has increased to 8-9 bar.