Caesar cipher wheel

A classroom tool with very little setup

The wheel lets students choose a letter shift, encode a message, and decode it again. I designed both the physical tool and a single-page guide so students could start using it with minimal explanation.

Decisions that made it practical

• Print in place. A tapered fit lets the inner disc rotate without requiring assembly after printing.
• Eight wheels per build plate. The 100 mm diameter leaves room for readable letters while making class sets practical to produce.
• One color change. Black-and-white lettering stays legible without repeated material changes.
• Optional detent. A spring-loaded insert adds indexing at each letter position.

I tested three versions to adjust the clearance between the disc and outer ring. The guide uses large type, numbered steps, and the same straightforward visual style as the wheel.

Trying it with students

A small group worked through the activity using the guide. They could turn the wheels easily and use them to encode and decode messages. Their feedback informed a revision to the decoding instructions.

The center also has a recessed circle for an optional engraved badge, allowing branded versions without redesigning the wheel.