What I had in mind was a simple on/off switch with a voltage controlled return relief so that you could adjust the smoothness of the "off-pedal" action. I think you would want it to go on hard and accurately then come off the clutch at a determinable rate. The other option would be to have a pull style (or similar to a grip handle on a motor-cycle) handle that adjusted a potentiometer to voltage control the return, then you would have full control over the clutch but would not get any noticeable feedback like you do through the pedal. Which imo makes it less user friendly. option 1 creates a sort of launch control system, and you could take it a step further and tie it into your throttle control to always have the smoothest launch. But that would require changing to a non-mechanical throttle control. Either way it wouldn't be too difficult to design. I just personally can't afford to proto-type. I have an automotive engineer I can goldfish this idea with. We were already discussing hydraulic set-ups for z-bar replacement.
When I drove Mack trucks for UPS, they had an air operated clutch. It took no more effort to operate then an accellerator pedal. It was like an in and out clutch. The pedal in the Mack was even identical to the accellerator pedal.
Pneumatics are nice, but you need an air compressor to run them. Semi's use air more than hydraulics because they have alot more room to run larger air compressors. Generally they use 1 or 2 air compressors to run everything from the brakes, to shocks, to clutches and horns. If you want to stick an air compressor in your trunk you can convert your car to all air stuff too. Pneumatics imo are more reliable than hydraulics, much less temperature sensitive. and they can be alot more forgiving on leaks in the system, just ramp up the air pressure down the leaky line until you get the replacement parts ready. Ramp up the pressure on a hydraulic line and it just runs out of fluid faster.
Hand clutch like you have drawn would take way too much force to over come the pressure plate. It would have to use some thing to "boost" the hand movement, but still not be on and off so as to be able to feather the clutch. An electic clutch that worked an accuator off a potentiometer on the shifter would be the best way to go. I'VE BEEN MARRIED 17 YEARS AND HAVE THE GRIP STENGTH!!!
I totally agree that being able to feather the clutch would be ideal I'm just not sure where you get any feedback to tell you how much you were feathering the clutch. Then again since were putting in fancy electronic controls we could put in a pressure sensor to let you know how much you were feathering it. It is also something that requires a more difficult design. I had in mind a design that anyone could buy off the shelf parts and replicate. This would be a much more specialized design. But, not really any harder to create. Ok so what we would want is a handle grip that we can put in something like this http://www.potentiometers.com/Series404.cfm which would be used to control something like http://www.alibaba.com/product-gs/338585915/electronic_pressure_control_ls_1_.html (this is actually a bad example it would not work with this application) which would actuate the slave cylinder in a hydraulic set-up. Thats just an off the cuff 15 minute research.
Volkswagen had electric clutch with their automatic transmission back in '69. If your knee touched the shifter it will disengage the clutch
