Mountain/speed drive cranks shift with a button you tap with your heel. no added lever.

it's in the place where the crank arm fits onto the spindle.

http://schlumpf.ch/antriebe_engl.htm

http://kinetics.org.uk/html/mountain_drive.shtml or http://www.foldabikes.com/

I got a Mountain drive for My Brompton 54t + a 15t on my AW3 hub,

in low the crank is in effect a 21.6t [it's hilly and then some, here]