Bicycle pump CW key
An ordinary bicycle pump - a natural starting point for building a "pump" CW key.
(The so called "pump" keys seldom have anything to do with real pumps. This one is an exception.)
Choose a party balloon to suit your taste and attach it to the pump nozzle. A short length of garden hose is used to hold the balloon tightly in place without air leaks.
Two oversized hose clamps are attached to the pump shaft. The ends of the steel bands are bended so that they come near each other. A paper clip is needed for contacts.
"Key up" position: empty balloon - no contact.
"Key down" position: air pressure in the balloon makes the contacts touch.
Keying cable is connected with alligator clips to the clamps.
Pneumatic CW on the air. Two hands are needed.