Concept Generation and Development

Based on the research carried out  initial ideas for a mechanical crab  generated and developed. The concept centres around the use of linkages to convert rotary motion into forward movement in a way that is reminiscent of a crab. It was my intention from the outset to design a creature that is sculptural and not something that tries to accurately mirror creature.

Initial sketches exploring how linkages might create forward motion

Investigating existing linkage mechanisms

 Development of the linkage design

Using Creo Elements each component was then accurately drawn and then modelled to further develop the design concept. By modelling the component first its proportions and aesthetics can be assessed prior to production and in doing so the 2D drawings required for laser cutting a given component are also produced. The images below detail both the 2D component profile and a perspective view of the component extruded.

After the modelling stage was complete a dedicated drawing page of the component was created in the drawing part of the Creo package. This was then saved as a DXF file and loaded into Coral Draw where it could be sent to print on the laser cutter.

Laser cut components

With these components a functional test rig was constructed to test the proposed mechanism. The components were assembled using m6 nuts and bolts which were mounted onto an MDF board as seen below.

 

The dowel in the centre of the picture represents an off centre cam that is attached to a circle that spins around a fixed centre point.

As the off centre cam circulates the fixed centre so the attached linkages alter the position of the legs.