3D-printed carbon fiber and elastomer bike saddle

Overview

Many bicycle saddles on the market today inadequately support the rider due  to over-reductionist designs. The “one size fits all” seats do not account for the varying anatomies of riders and can cause severe discomfort, numbness, and pain; they are even associated with chronic urogenital pathologies. Our team sought to address these issues by designing a system for producing a fully customizable bike seat.

Objectives

– Develop a method to accurately collect input measurements (i.e., sit bone breadth) of an individual to inform the customization of a bike seat for that individual. 
– Use CAD to model the base and elastomer top of the bicycle seat so that both are parametrizable for a wide range of individuals’ input measurements.  
– Create function to vary seat thickness and lattice structure in MATLAB and nTop software to optimize the function, support, and comfort of the elastomer top. 
– Manufacture the customized components of the seat using additive manufacturing and carbon fiber layups.  
– Unify all the components of the system so that collecting user input measurements, adjusting the CAD files of the elastomer top and base, and manufacturing the seat are streamlined and capable of producing a complete bicycle seat customized to an individual.

Approach

– Define customer and sponsor needs and decide what the final outcomes are.
– Disassemble seats on the market to investigate their components, identify strengths and weaknesses, and brainstorm what the team’s improved seat design should look like.
– Develop a CAD model of the elastomer top of the seat.
– Print the elastomer top and reiterate on the design multiple times before deciding on a final CAD model.
– Develop a way of collecting input measurements from the customer: conduct a small-scale study for measuring ischial tuberosity (sit bone) breadth on a range of participants; determine impression foam as the best mechanism for measuring an individual’s sit bone breadth.
– Model the saddle base using an existing seat on the market; parametrize both the seat base and the elastomer top to be based on sit bone breadth as a global variable.
– Develop a MATLAB stiffness map to vary thickness throughout the elastomer top based on sit bone breadth.
– Use nTopology to relate the MATLAB map to varying lattice densities on the elastomer top.
– Print the lattice elastomer top using a 3D resin printer; reiterate printing techniques.
– Print 3 different seat bases for 3 varying sit bone breadths using 3D printed PLA; base the varying sit bone breadths on data from the sit bone study.
– Use vacuum bagging to apply carbon fiber layups around the PLA base cores to reinforce the seat bases.
– Attach the elastomer top to the carbon fiber base to complete the assembly of a fully customized bike seat.

Outcomes

– Fully parametrizable CAD models of seat base and elastomer top. 
– Fully customizable variable stiffness map. 
– System to collect user measurements to input as global variables for the stiffness map and CAD files. 
– Final customized seat featuring carbon fiber base and elastomer lattice top 
– Bonus Outcome (supplements the initial project scope): method of manufacturing custom carbon fiber rails using 3D printed molds.