From Eco-Vehicles

Found this, might be useful. Six years old vid.

linear pedal cycle.

Not only


But also,

Doesn't have to have an exact linear travel, can arc on a pivot too.
Essentially at the heart is 2, single sprocket freewheels.
Interesting but... (always a but)... If it is/was so much more efficient we would have seen a lot more of it in production bikes today I think.
I think the video exposed the benefit and the "flaw" in it. It is like being on a stair-stepper because there is very little let up in the cycle the "torque/load" on the legs doesn't really let up its a full load for each pedal-stroke and not a varying load. I suspect if it was such a giant-leap forwards the mainstream cycle manufacturers would have gobbled it up with relish and put it out there.

On that second video, if there is a freewheel on each side of the rear-wheel and a driving arm with a foot platform on the end once you have reach a certain speed how will you ever get any faster?
There's no gearing, you are just pulling 2 chains over a limited distance and then spring-returning them to re-engage on the ratchet IF you can depress the pedal fast enough to get the pawls to re-engage, and IF the return spring is strong enough to pull the chain back YOU are working against that spring on the power stroke and that's wasted energy isn't it?

Thanks for sharing Martin. :)