The problem

Canard Design was developing a new wheelchair, which needed to fold flat and to be light enough to be carried quickly by paramedics. It needed a frame that would be cost effective to make, easy to keep clean, durable and light weight. Coupland Bell was given the task of designing a new frame that would be lighter than the first prototype.

Our solution

The first prototype used thin wall highly-stressed steel tubing from Reynolds. Aluminium and carbon fibre were the clear choices for a lighter design.

A comparison was made by building FEA models of the largest component in the frame, in both materials. Although slightly heavier, aluminium was chosen because it would be easier to modify when further changes were needed on the new prototype and it would be more cost effective for a small initial production batch.

Our consultants also investigated whether to share the loads between the frame and the panels. Although this could save some weight, it was not done in the prototype because speed of assembly and ease of changing damaged panels in service were considered more important. By also redesigning and deleting some parts the weight of the chassis/ frame was reduced from 9.75 to just 3.7kg.