Heim joints and a piece of steel tubing hinged to the steering column, and another rod or tube attached with heim joints to the lever arm are the basics behind a hand clutch. It can even have fancy bends in it as long as the leverage is correct to allow hand pressure to overcome the return spring and the pressure plate springs. If it's built right, the clutch can still be operated with a foot.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!