The Mathematical Bridge
Built by Chris Warrell in April 2009 for the Building Bridges Secretary’s Challenge
This model was built for the Secretary’s Challenge to build a bridge with a span of 24½”.
Using my newly acquired blue/gold № 9 set (more correctly, newly built up, since it’s taken a while to get the full contents) this model is based on a bridge in Queens College at The Backs in Cambridge. The original is of timer construction and was built in 1749 by James Essex the Younger to the design of William Etheridge (1709 — 1776). It was repaired in 1866 and subsequently rebuilt to the same design in 1905, but in teak instead of the original oak. The joints of the original bridge were fastened by iron pins, but the present version uses nuts and bolts.
The Meccano model is based solely on a photograph in the book Bridges of Britain by Eric de Mare.
The construction of the model is quite straightforward, with angle girders being used for the newel posts, main beam and top rail. All other struts and posts are represented by strips of various lengths. Use of the slotted holes in the angle girders meant that, despite the odd geometry of the model, it was possible to have at least two fixing points for all but the most minor of strips. The bridge deck is mainly 5½” x 3½” plates overlaid with 12½” strip plates.