One of the kayak lines we carry at our store is Riot Kayaks - in particular their Mako models in the 10' and 12' versions. Both use the same traditional bicycle-motion pedal drive - the "Impulse Drive " - known for its lower-than-normal cost which helps keep the overall price of their models well below the comparable competition.
A key to the lower cost point is the use of a simple, but very effective plastic gear train inside the drive. We deconstruct one of the drives and take a peek inside. Check out the video below!