I have interested in walking bicycle. For the concept is just bicycle that you don't cycling pedal but stepping or striding to drive wheel
Which leads me to think that is it better if we use linear or ellipse motion of leg to transmit to bicycle
The closest mechanic I could think is piston crankshaft like a car. It convert linear motion to rotation
How disadvantage of the mechanic compare to cycling motion?
The biggest problem with a "two cylinder" crankshaft is that there is a dead spot in the torque curve whenever either "piston" is at TDC or BDC.
When you have your feet directly on the pedals of a conventional circular crank, you actually have the ability to apply force over greater than a 180° arc — by a combination of flexing your ankles and pushing forward/backward with your thigh muscles — which eliminates the dead spot.
If you try to use a mechanical connecting rod with a crankshaft, you need some other way to eliminate the dead spot. This typically involves using more than two pistons, or by incorporating a large flywheel into the mechanism. None of this is practical or desirable on a bicycle.
I have seen toy vehicles for small children that use such a mechanism. but invariably, they need to put their feet down on the ground from time to time to push themselves out of the dead spot.
