What We Learned Developing a Retractable Cubby Lid

Not every TRUNKWERKS prototype becomes a product.

We recently explored a retractable lid for the BMW i4 trunk-side storage platform. The goal was to conceal the adapter and storage beneath a sliding cover while keeping access convenient.

After multiple printed prototypes and a full-size vehicle-fit test, we have decided to shelve the design.

What we were trying to create

The concept used a flexible curtain made from rigid, articulated slats. It would travel through side tracks and roll around a bearing-supported cylinder when opened.

The surrounding frame also needed to install above the existing tray and carrier without compromising adapter access.

What worked

The articulated slat design proved flexible in physical testing. The curtain-to-cylinder connection was refined until it held snugly, and the bearing interfaces fitted successfully.

The complete prototype also showed that the curtain could move smoothly when guided by hand and the cassette halves were held in better alignment.

Those were useful results, but they did not establish a finished, independently functioning system.

Where the prototype fell short

The final prototype exposed several problems:

• The assembled unit was too large for the vehicle’s cubby space, and assembling it in place was not practical.

• The cassette connections did not hold the halves together reliably enough; a clamp was needed during bench assembly.

• Curtain travel needed assistance rather than consistently working from the handle alone.

• Removing print supports took approximately an hour, and small nut-retaining pieces did not print successfully in the tested 0.6 mm nozzle setup.

These were not finishing details. They affected fit, assembly, printing and everyday operation—the fundamentals of a usable product.

What we learned

A successful hinge or roller test does not prove that the complete system will work in the vehicle. The available space, insertion path, assembly access and alignment have to work together.

Future development needs to establish those constraints earlier, before committing to a complete mechanical prototype.

Development status

The retractable lid is shelved. It is not a production release, is not included in the current product, and is not available to purchase or download.

We are proud of the work and what it taught us. But adding a feature only makes sense if it improves the experience. For now, our focus remains on the practical storage and adapter-retention features of the released TRUNKWERKS platform.