Friday, January 9, 2015

Auckland's rolling lift draw bridge

I recently came across Auckland's rolling lift draw bridge, which I have seen before, but have not paid any attention to.  This time I noticed a gear rack embedded in the road way and took a couple of photos to try to understand how it works,  This particular bridge was supplied by the Cleveland Bridge and Engineering Company in 1932 but it seems the rolling lift design originated by William Scherzer who died in 1893.  The drive pinion retracts the bridge along the rack located on top of two frames anchored to the bridge abutment.  Two curved edges at the end of the bridge truss are engaged with the gear racks embedded in the road and the whole structure rolls up and back out of the way of passing boats.

I had to make a paper prototype model to illustrate and understand the mechanism because I haven't seen the bridge working.  Notice how the pinion stays at the same level as the drive motor and gear train revolve around it.  William Scherzer gets my vote for induction into the Tinker's Hall of Fame.