Mechanical & product design
A tricycle, built from scratch
A functional children’s tricycle designed around user measurements and built through CAD, metal fabrication and woodworking.
Why I started
I set out to design and build a functional children’s tricycle around user measurements.
My contribution
I worked from CAD through mechanical design, MIG welding, woodworking and assembly.
Current state
Completed functional prototype. Workshop photographs and riding footage document the build; formal load and durability tests are not recorded here.
Designing around a person
The brief was to design and build a functional tricycle for children. Child anthropometric measurements informed the dimensions and mechanical requirements, connecting the design to the intended user. Seating position, reach, frame scale and comfort had to work together with stability, strength and the parts I could actually manufacture.
From CAD to fabrication
I used Onshape and SketchUp for the design, adapted a bicycle-style differential mechanism for two driven wheels, and built the physical prototype using metal tubing, MIG welding, woodworking and assembly.
The build reuses a bicycle front section for steering, the front wheel and the crank-and-pedal assembly. I connected it to a custom rear structure with triangular bracing, an axle assembly and two smaller rear wheels. A chain runs from the pedal drive to the rear sprocket. The workshop photographs show both the rear structure on its own and its integration into the assembled tricycle.
Making and assembling the prototype
The build combined MIG welding, metalworking and woodworking, with custom component interfaces, reinforced load-bearing joints and finishing work. Each design decision had to survive the move from CAD into real materials and assembly.
The flat wooden seat sits on upright metal supports above the rear structure. The fabrication photograph shows a bicycle frame tube held in a vice during modification; the axle close-up shows the sprocket, chain, supports and welded joints. These interfaces were where the reused bicycle components had to meet the parts I made.
The custom drivetrain transmitted power to two rear wheels within the child-sized frame; it could not simply reuse adult bicycle dimensions. The completed functional tricycle combines CAD, mechanical reasoning, materials, fabrication and practical assembly.
- Design around user requirements.
- Make fabrication constraints part of the design.
- Carry the work through to a functional physical prototype.
The build in use
The supplied photographs document the workshop build, and the riding video shows the assembled tricycle being pedalled and steered outdoors. The rider is supported on the wooden seat while the custom frame and two rear wheels travel together. This is a practical demonstration of a rideable prototype.
The video does not provide measured load capacity, braking distance, durability or a formal child-user evaluation. Those would need a separate test programme. The project is completed; original CAD, dimensions and recorded mechanical tests would add further detail to the build documentation.
From workshop to a rideable build
These photographs show the rear structure, the seat and pedal arrangement, and the frame modification work. The riding video shows the assembled tricycle moving under pedal power and being steered outdoors.
27-second riding demonstration, presented as a silent web copy. A rider pedals the tricycle along a paved area and steers around a bend, showing the wooden seat, custom frame and rear wheels in use.
Download riding video