Ergonomic Recumbent Bike Seat

As a member of UC Berkeley Human Powered Vehicle, I was tasked with designing an ergonomic seat for our rider.

CAD Model

Design Considerations

When designing the seat, ergonomics were a top priority.  Our research showed that the comfort and cycling performance of a recumbent trike depends on 3 primary angles – the body body configuration angle (BCA), the hip orientation angle  (HOA), and the knee angle (KA). In a recumbent position, a BCA of 130 degrees, HOA of -5 degrees and a KA below 90 degrees maximizes comfort and power delivery while also keeping aerodynamic drag to a minimum. 

Diagram showing key body joint angles

I then took measurements of our intended driver (95th percentile male) as shown in the table below, and used these to scale the seat measurements accordingly. A lumbar support height of 11” with a back angle (BA) of 50 degrees was used to provide our driver with maximum support and comfort.

Measurement DefinitionDimension (Inches)
Top of head to base of neck10
Shoulder to hip21
Hip to knee21
Knee to ankle18
Shoulder to wrist25
Width of shoulders22
Width of hips15
Overall Height72

I primarily used Fusion360 to CAD the seat, and used the surface modeling workspace to create the general shape of the seat using sweeps and cuts. I then used the thicken tool to add depth, and finally filleted sharp edges before importing the model into SolidWorks to use in the final assembly.