Those two bouncers are mine.. the black one I built and sold in @1992, the green one on the striped Ford is my first Whymcycle, built in 1988..It's been ridden by many thousands of folks since..
Just this week been following up the shenanigans you get up to on bounce bikes. The art car race looks amazing as a test of ingenuity and practicality
Having messed up knees I was wondering if a bounce whymcycle may be a solution.