Stabli: Spill-Minimizing Beverage Holder

Bicycles and coffee don't mix easily. 59% of casual bikers surveyed displayed interest in investing in a cup holder to minimize spillage of their daily coffee during a ride. Stabli utilizes material properties of urethane and plastic to provide users with spill minimization of unsealed takeout beverages. Aimed towards commuters and casual cyclists, Stabli keeps drinks accessible at all times, allowing for a more enjoyable ride. Collaboration with Basma Aiouche, Jordan Hoffmann, Molly McLaughlin, Kevin Shannon, Salute Wonghiriwat, Jack Yao, and Emily Ye.

Won People's Choice Award at RISD-MIT final presentation.

Patent Pending.

Exhibited at Global Grad Show, Dubai, UAE (pending, Nov 2017).

RISD-MIT STUDIO 2.739/15.783 Spring 2017 Product Design and Development

Primary Market Commuter and casual cyclists.

Role Industrial design, prototyping, graphic design, branding.

Categories: product design, engineering


  1. pitch ideas, Real-Win-Worth-it Assessment
  2. divide into teams
  3. user and market research
  4. concept generation and selection
  5. target specifications
  6. key uncertainty and failure modes addressed
  7. prototyping
  8. CTF Specifications
  9. bill of materials, life cycle analysis
  10. functional testing, customer feedback
  11. patent
  12. financial model
  13. branding

Initial pitch of concept proposed for a better way of holding a takeout coffee while riding a bicycle. Each member of the team generated several ideas on how to minimize spillage, and all the ideas were dissected and combined onto a single sheet.

After narrowing down to the three most promising concepts (Hanging Weight, Spring Suspension, and Spill Proof Lid), we decided to make a series of works-like models to help further downselect the options. We constructed models that functioned as much like the three concepts as possible while at the same time using simple and easy-to-find materials.

Highly mechanical concepts were explored in the initial stage. A talk with a Ph.D student introduced us with the possibility of using rubber as a damping material. In order to derive the best performing dimension of the “neck,” a number of Design of Experiments (DOE) was done with 4 variables (width, length, and height of the neck, and weight of the cup) in relation to acceleration measured by the gyroscope in the cup.

Preliminary testing.

Following the concept development and DOE, the team arrived at the final design outline:

  1. The product is easy to remove and install.
  2. The product is manufactured out of ABS and TPU, double shot injection molded, with some metal parts.
  3. The neck of the product provides torsional rotation while being strong enough to withstand the weight of the cup.
  4. The clamping action, the axial rotation of the cup receptacle, and the torsional rotation of the neck are the primary motion of the product.

By discovering engineering and design constraints from earlier prototypes and design of experiments, the team was able to design the final alpha prototype.

Materials were selected to reduce the number of parts and increase recyclability through overmolding. Thermoplastic elastomer (TPE) can be overmolded with olefinic materials without adhesive since the two materials form a chemical bond upon double shot molding. The overmolded part can be reground, melted, and reprocessed to be recycled since both materials in the part are thermoplastics. Thermoplastic polyurethane (TPU) bonds well to polycarbonate (PC), acrylonitrile butadiene styrene (ABS), PC ABS composite, and certain types of nylon (PU), while providing required shore hardness for our product to function properly. Urethane also has good damping properties and is durable (wear-resistant).

Pictured is the beta prototype with a generic bicycle mount to test the concept of overmolding and observing the interaction between different hardness materials.

Both alpha and beta prototypes use carbon fiber-fused nylon 3D print pieces and urethane rubber. The materials are similar in mechanical characteristics to ABS and TPU, the materials for the production version of the product.

In order to reach the final alpha prototype, 10 CAD generations, 10 3D print batches, and lots more molds were necessary.

Final molds and cast parts. Platinum cure silicone molds. SLA resin prints, carbon fiber-fused nylon prints. Urethane rubber.

Bicycle CAD model by Pratap Singh, GrabCAD.

Bicycle CAD model by Pratap Singh, GrabCAD.