This is easily one of the most unusual of bicycles ever made!
1994 Trialtir Integrale
1994 Trialtir Integrale
Very unusual two wheel drive bike. Not too sure that I can describe the action well enough to be understood but here it goes. The handlebars go forwards and backwards using the pivots on the fork crown. The stem has a forward bumper to limit the forward travel. The lower end of the legs, attached to the bars, has a cable that attaches to a cog mounted to the back of the fork. The cog has an internal wound spring to return the cog with the forward handlebar motion. The fork mounted cog drives a single cog freewheel, that is attached to the front wheel, via a regular bike chain. So basically, you pull back on the handlebars which pulls the cable on the end of the leg attached to the bars, the cable rotates the upper cog which drives the freewheel via the chain, pushing the bars forward allows the spring in the upper cog to return the cog to prepare for the next power stroke. There is also an additional shifter on the handlebars which will lock the stem so it can be used as a conventional bike.
While it is all somewhat complicated, and uses pretty inexpensive parts, it actually doesn't work all that bad. You definitely get a much better upper body workout and you can feel a little extra boost while pulling the bars back. It would be pretty tricky to use off road and when the bars are in the rearward position, the controls are really awkward to reach.